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1.
  • Faivre-Rampant, O., et al. (författare)
  • Peroxidase activity, ethylene production, lignification and growth limitation in shoots of a nonrooting mutant of tobacco
  • 1998
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 36:12, s. 873-877
  • Tidskriftsartikel (refereegranskat)abstract
    • The rooting recalcitrant rac Nicotiana tabacum cv Xanthi mutant has been multiplied in vitro under the form of shoots in parallel to wild-type. rac Shoots grew at a lower rate and did not root whatever the treatments when compared to those of wild-type shoots. They were characterized by a higher lignin level, a higher total specific peroxidase activity with higher activity of both acidic and basic isoperoxidases (although missing and supernumerary isoenzymes were observed), and higher ethylene production. These observations might be causally related to growth inhibitions as similar incidences have been noted in different stress-induced growth limitation, through cell wall rigidification and auxin catabolism. The relationship between these aspects and rooting recalcitrance remains to be explored. (C) Elsevier, Paris.
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2.
  • Hjortswang, H I, et al. (författare)
  • KNOTTED1-like homeobox genes of a gymnosperm, Norway spruce, expressed during somatic embryogenesis
  • 2002
  • Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 40:10, s. 837-843
  • Tidskriftsartikel (refereegranskat)abstract
    • Two Norway spruce (Picea abies (L.) Karst.) genes belonging to class I of the KNOTTED1-like homeobox (KNOX) genes, HBK2 and HBK3, were cloned with PCR-based methods. The expression of these and a previously characterised related gene, HBK1, in different organs and during somatic embryogenesis was studied with RTPCR. Transcripts of all three genes were detected in stems, roots and in cone buds, but not in needles. HBK1 and HBK3 are expressed throughout development in a normal cell line with embryogenic potential and in a cell line unable to form somatic embryos. HBK2 is expressed in the normal cell line, but not in the developmentally arrested cell line. This suggests that the HBK2 gene is involved in the somatic embryo development.
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3.
  • Aliakbari, Massume, et al. (författare)
  • Rubisco activase A (RcaA) is a central node in overlapping gene network of drought and salinity in Barley (Hordeum vulgare L.) and may contribute to combined stress tolerance
  • 2021
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 161, s. 248-258
  • Tidskriftsartikel (refereegranskat)abstract
    • Co-occurrence of abiotic stresses, especially drought and salinity, is a natural phenomenon in field conditions and is worse for crop production than any single stress. Nowadays, rigorous methods of meta-analysis and systems biology have made it possible to perform cross-study comparisons of single stress experiments, which can uncover main overlapping mechanisms underlying tolerance to combined stress. In this study, a meta-analysis of RNA-Seq data was conducted to obtain the overlapping gene network of drought and salinity stresses in barley (Hordeum vulgare L.), which identified Rubisco activase A (RcaA) as a hub gene in the dual-stress response. Thereafter, a greenhouse experiment was carried out using two barley genotypes with different abiotic stress tolerance and evaluated several physiochemical properties as well as the expression profile and protein activity of RcaA. Finally, machine learning analysis was applied to uncover relationships among combined stress tolerance and evaluated properties. We identified 441 genes which were differentially expressed under both drought and salinity stress. Results revealed that the photosynthesis pathway and, in particular, the RcaA gene are major components of the dual-stress responsive transcriptome. Comparative physiochemical and molecular evaluations further confirmed that enhanced photosynthesis capability, mainly through regulation of RcaA expression and activity as well as accumulation of proline content, have a significant association with combined drought and salinity stress tolerance in barley. Overall, our results clarify the importance of RcaA in combined stress tolerance and may provide new insights for future investigations. 
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4.
  • Andersson, Inger, et al. (författare)
  • Structure and function of Rubisco
  • 2008
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 46:3, s. 275-291
  • Tidskriftsartikel (refereegranskat)abstract
    • Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the major enzyme assimilating CO2 into the biosphere. At the same time Rubisco is an extremely inefficient catalyst and its carboxylase activity is compromised by an opposing oxygenase activity involving atmospheric O2. The shortcomings of Rubisco have implications for crop yield, nitrogen and water usage, and for the global carbon cycle. Numerous high-resolution crystal structures of different forms of Rubisco are now available, including structures of mutant enzymes. This review uses the information provided in these structures in a structure-based sequence alignment and discusses Rubisco function in the context of structural variations at all levels – amino acid sequence, fold, tertiary and quaternary structure – with an evolutionary perspective and an emphasis on the structural features of the enzyme that may determine its function as a carboxylase.
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5.
  • Askerlund, Per, et al. (författare)
  • Detection of distinct phosphorylated intermediates of Ca2+-ATPase and H+-ATPase in plasma membranes from Brassica oleracea
  • 1993
  • Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 31:5, s. 787-791
  • Tidskriftsartikel (refereegranskat)abstract
    • Two distinct phosphorylated intermediates representing the Ca2+-ATPase and H+-ATPase, respectively, were detected after phosphorylation of plasma membranes from cauliflower (Brassica oleracea L.) inflorescences with [gammaP-32]ATP and separation of polypeptides in an acidic gel. A 116 kDa polypeptide was identified as a Ca2+-ATPase by its Ca2+-dependent phosphorylation which was enhanced by La3+. A second polypeptide (105 kDa) also phosphorylated in the absence of Ca2+ and was identified as the H+-ATPase by immune blotting.
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6.
  • Batista-Santos, Paula, et al. (författare)
  • Is salt stress tolerance in Casuarina glauca Sieb. ex Spreng. associated with its nitrogen-fixing root-nodule symbiosis? An analysis at the photosynthetic level
  • 2015
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 96, s. 97-109
  • Tidskriftsartikel (refereegranskat)abstract
    • Casuarina glauca is an actinorhizal tree which establishes root-nodule symbiosis with N-2-fixing Frankia bacteria. This plant is commonly found in saline zones and is widely used to remediate marginal soils and prevent desertification. The nature of its ability to survive in extreme environments and the extent of Frankia contribution to stress tolerance remain unknown. Thus, we evaluated the ability of C. glauca to cope with salt stress and the influence of the symbiosis on this trait. To this end, we analysed the impact of salt on plant growth, mineral contents, water relations, photosynthetic-related parameters and nonstructural sugars in nodulated vs. non-nodulated plants. Although the effects on photosynthesis and stomatal conductance started to become measurable in the presence of 200 mM NaCl, photochemical (e.g., photosynthetic electron flow) and biochemical (e.g., activity of photosynthetic enzymes) parameters were only strongly impaired when NaCl levels reached 600 mM. These results indicate the maintenance of high tissue hydration under salt stress, probably associated with enhanced osmotic potential. Furthermore, the maintenance of photosynthetic assimilation potential (A(max)), together with the increase in the quantum yield of down-regulated energy dissipation of PSII (Y-NPQ), suggested a down-regulation of photosynthesis instead of photo-damaging effects. A comparison of the impact of increasing NaCl levels on the activities of photosynthetic (RubisCO and ribulose-5 phosphate kinase) and respiratory (pyruvate kinase and NADH-dependent malate dehydrogenase) enzymes vs. photosynthetic electron flow and fluorescence parameters, revealed that biochemical impairments are more limiting than photochemical damage. Altogether, these results indicate that, under controlled conditions, C glauca tolerates high NaCl levels and that this capacity is linked to photosynthetic adjustments.
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7.
  • Berglund, Torkel, et al. (författare)
  • Nicotinamide; antioxidative and DNA hypomethylation effects in plant cells
  • 2017
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 118, s. 551-560
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of nicotinamide (NIC) and its natural plant metabolites nicotinic acid (NIA) and trigonelline (TRIG) were studied with respect to defense in plant cell cultures. NIC and NIA could protect against oxidative stress damage caused by 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH), which generates free radicals. Damage was analyzed as DNA strand breaks in cell cultures of Pisum sativum (garden pea), Daucus carota (carrot), Populus tremula L. × P. tremuloides (hybrid aspen) and Catharanthus roseus (Madagascar periwinkle), monitored by single cell gel electrophoresis (comet assay), and assays of cell leakage in C. roseus. The activities of aconitase and fumarase enzymes, which have key roles in energy metabolism, were analyzed in P. sativum cultures after treatment with NIC or NIA. Aconitase activity was increased by NIA, and fumarase activity was increased by both compounds. These compounds were shown to promote glutathione metabolism in P. sativum cultures, and NIC was shown to have a global DNA hypomethylating effect. Neither TRIG nor poly(ADP-ribose) polymerase (PARP) inhibitor 3-aminobenzamide offered any protection against DNA damage or cell leakage, nor did they promote aconitase or fumarase activities, or glutathione metabolism. By this broad approach addressing multiple biochemical factors and different plant species, we demonstrate that NIC and NIA protect plant cells from oxidative stress, and that NIC clearly exerts an epigenetic effect; decreased DNA methylation. This indicates that these compounds have important roles in the regulation of metabolism in plant cells, especially in connection to stress.
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8.
  • Björn, Lars Olof (författare)
  • On the history of phyto-photo UV science (not to be left in skoto toto and silence).
  • 2015
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 93:Online 30 September 2014, s. 3-8
  • Forskningsöversikt (refereegranskat)abstract
    • This review of the history of ultraviolet photobiology focuses on the effects of UV-B (280-315 nm) radiation on terrestrial plants. It describes the early history of ultraviolet photobiology, the discovery of DNA as a major ultraviolet target and the discovery of photoreactivation and photolyases, and the later identification of Photosystem II as another important target for damage to plants by UV-B radiation. Some experimental techniques are briefly outlined. The insight that the ozone layer was thinning spurred the interest in physiological and ecological effects of UV-B radiation and resulted in an exponential increase over time in the number of publications and citations until 1998, at which time it was realized by the research community that the Montreal Protocol regulating the pollution of the atmosphere with ozone depleting substances was effective. From then on, the publication and citation rate has continued to rise exponentially, but with an abrupt change to lower exponents. We have now entered a phase when more emphasis is put on the "positive" effects of UV-B radiation, and with more emphasis on regulation than on damage and inhibition.
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9.
  • Braumann, Ilka, et al. (författare)
  • Reduced chlorophyll biosynthesis in heterozygous barley magnesium chelatase mutants
  • 2014
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 78, s. 10-14
  • Tidskriftsartikel (refereegranskat)abstract
    • Chlorophyll biosynthesis is initiated by magnesium chelatase, an enzyme composed of three proteins, which catalyzes the insertion of Mg2+ into protoporphyrin IX to produce Mg-protoporphyrin IX. In barley (Hordeum vulgare L.) the three proteins are encoded by Xantha-f, Xantha-g and Xantha-h. Two of the gene products, XanH and XanG, belong to the structurally conserved family of AAA+ proteins (ATPases associated with various cellular activities) and form a complex involving six subunits of each protein. The complex functions as an ATP-fueled motor of the magnesium chelatase that uses XanF as substrate, which is the catalytic subunit responsible for the insertion of Mg2+ into protoporphyrin IX. Previous studies have shown that semi-dominant Xantha-h mutations result in non-functional XanH subunits that participate in the formation of inactive AAA complexes. In the present study, we identify severe mutations in the barley mutants xantha-h.38, -h.56 and -h.57. A truncated form of the protein is seen in xantha-h.38, whereas no XanH is detected in xantha-h.56 and -h.57. Heterozygous mutants show a reduction in chlorophyll content by 14-18% suggesting a slight semi-dominance of xantha-h.38, -h.56 and -h.57, which otherwise have been regarded as recessive mutations
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10.
  • Carlsson, Georg (författare)
  • Phosphorous deficiency decreases nitrogenase activity but increases proton efflux in N-2-fixing Medicago truncatula
  • 2011
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 49, s. 458-460
  • Tidskriftsartikel (refereegranskat)abstract
    • Effects of Sinorhizobium strain and P nutrition on N-2-dependent growth, nitrogenase activity and proton efflux by nodulated roots were investigated in the model legume Medicago truncatula cultivar Jemalong grown in hydroaeroponic culture in symbioses with Sinorhizobium meliloti strains 102F51 and 2011. Sinorhizobium strain had strong effects on nitrogenase activity and N-2-dependent growth, with S. meliloti 102F51 being the more efficient strain. Apparent and total nitrogenase activities, measured by hydrogen evolution in air and argon, respectively, were drastically reduced in plants supplied with 5 mu mol P plant(-1) week(-1) as compared with 15 mu mol P plant(-1) week(-1). There was a net proton efflux as soon as 2 weeks after inoculation and, in contrast to the effect of P nutrition on nitrogenase activity, P deficiency increased total and specific proton effluxes, irrespective of Sinorhizobium strain. (C) 2011 Elsevier Masson SAS. All rights reserved.
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11.
  • Christiernin, Maria (författare)
  • Lignin composition in cambial tissues of poplar
  • 2006
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 44:11-12, s. 700-706
  • Tidskriftsartikel (refereegranskat)abstract
    • The cambial tissues of a Populus balsamifera, Balsam poplar clone were studied during a growth season. The Klason and acid-soluble lignin contents were determined as well as the carbohydrate monomer distribution and the protein content. Both the phloem and the xylem sides of the cambial region were examined. The samples were analyzed by thioacidolysis and structures of dimeric products were determined by mass spectrometry after desulphuration. Chemical analysis of samples during the growth season was combined with microscopy of embedded specimens that showed the state of cell differentiation at the time of sampling. In spring and early summer, growth is very rapid and the intention was to collect tissue in which exclusively the middle lamella/primary cell wall had begun to lignify. The Klason lignin, protein content and carbohydrate monomer distribution showed that all the specimens from the cambial tissues sampled during a growth season contained predominantly middle lamella and primary walls; except for the developing xylem sampled in August where the carbohydrate composition showed that secondary walls were present. Thioacidolysis showed that the lignin from the cambial tissues had more condensed structures than the lignin from the reference balsam poplar clone wood. More guaiacyl than syringyl units were detected and mass spectrometry showed that the cambial tissues contained more lignin structures with end-groups than the reference sample. These results suggest that lignification in the cambial layer and early developing xylem may take place predominantly in a bulk fashion during the summer. (c) 2006 Published by Elsevier Masson SAS.
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12.
  • Christiernin, Maria, et al. (författare)
  • Lignin isolated from primary walls of hybrid aspen cell cultures indicates significant differences in lignin structure between primary and secondary cell wall
  • 2005
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 43:8, s. 777-785
  • Tidskriftsartikel (refereegranskat)abstract
    • Hybrid aspen (Populus tremula x tremuloides) cell cultures were grown for 7, 14 and 21 days. The cell cultures formed primary cell walls but no secondary cell wall according to carbohydrate analysis and microscopic characterization. The primary walls were lignified, increasingly with age, according to Klason lignin analysis. Presence of lignin in the primary walls, with a higher content in 21-day old cells than in 7-day old cells, was further Supported by phloroglucinol/HCI reagent test and confocal microscopy after both immunolocalization and staining with acriflavin. Both laccase and peroxidase activity were found in the cultures and the activity increased during lignin formation. The lignin from the cell culture material was compared to lignin from mature aspen wood, where most of the lignin originates in the secondary cell wall, and which served as our secondary cell wall control. Lignin from the cell walls was isolated and characterized by thioacidolysis followed by gas chromatography and mass spectrometry. The lignin in the cell cultures differed from lignin of mature aspen wood in that it consisted exclusively of guaiacyl units, and had a more condensed structure. Five lignin structures were identified by mass spectrometry in the cell suspension cultures. The results indicate that the hybrid aspen cell culture used in this investigation may be a convenient experimental system for studies of primary cell wall lignin.
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13.
  • Christiernin, Maria (författare)
  • Structure of lignins in developing xylem of Norway spruce
  • 2006
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 44:11-12, s. 693-699
  • Tidskriftsartikel (refereegranskat)abstract
    • The developing xylem in a Norway spruce (Picea abies) clone was investigated during a growth season and compared to lignin from sapwood of the same tree clone. Klason and acid-soluble lignin contents were determined as well as the carbohydrate monomer distribution and protein content. By analyzing lignin thioacidolysis products, it was shown that only guaiacyl units could be detected in the materials, and the relative amount of beta-O-4' bonds was assessed. Monomeric and selected dimeric lignin products were identified by mass spectrometry. The specimens were embedded and thin sections examined by microscopy to determine the state of cell differentiation in the samples. In the spring and early summer, growth was very rapid and the intention was to collect tissue in which exclusively the middle lamella/primary cell wall had begun to lignify. Combining data regarding Klason lignin, protein content and carbohydrate monomer distribution with microscopy, it was found that the developing xylem sample from mid-June contained lignin from exclusively middle lamella/primary wall. The Klason lignin content in the developing xylem during the growth season was 20%, 5% and 10% in April, June and August, respectively. Thioacidolysis showed that the lignin had more condensed structures than lignin from the reference Norway spruce clone wood. Mass spectrometry showed that the developing xylem specimens from June and August contained more lignin structures with end-groups than the reference sample. These results suggest that lignification in the cambial layer and early developing xylem may take place more in a bulk fashion during the summer.
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14.
  • Ciereszko, I, et al. (författare)
  • Glucose and mannose regulate the expression of a major sucrose synthase gene in Arabidopsis via hexokinase-dependent mechanisms
  • 2002
  • Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 40:11, s. 907-911
  • Tidskriftsartikel (refereegranskat)abstract
    • Sucrose synthase (SuSy) is an important enzyme involved in sucrose synthesis/breakdown in all plants. Sus1, a major SuSy gene in Arabidopsis thaliana, was upregulated by sucrose, glucose and D-mannose, but not 3-O-methylglucose, when those compounds were fed to excised leaves. Mannos, was more effective than glucose or sucrose in the induction of Sus1, with strong effects observed at a concentration as low as 20, mM. When fed to the excised leaves, N-acetyl-glucosamine, an inhibitor of hexokinase (HXK) enzymatic activity, decreased sucrose- and glucose-dependent, but not mannose-dependent, upregulation of Sus1. The sucrose/glucose-dependent Sus1 expression was strongly induced in transgenic Arabidopsis HXK-overexpressing (OE) plants, whereas mannose-dependent Sus1 expression markedly decreased in OE, but not in HXK-"antisense", Arabidopsis plants. Feeding with sucrose resulted in a marked increase of glucose content in leaves, suggesting that it is glucose rather than sucrose that serves as a signal in upregulating Sus1 expression in sucrose-fed plants. The data suggest that Sus1 is regulated by a HXK-dependent pathway, with glucose and mannose effects differentially sensed/transmitted via the HXK step. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.
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15.
  • Dimitrova Mårtensson, Linda-Maria, et al. (författare)
  • Water use efficiency and shoot biomass production under water limitation is negatively correlated to the discrimination against 13C in the C3 grasses Dactylis glomerata, Festuca arundinacea and Phalaris arundinacea
  • 2017
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 113, s. 1-5
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate change impacts rainfall patterns which may lead to drought stress in rain-fed agricultural systems. Crops with higher drought tolerance are required on marginal land with low precipitation or on soils with low water retention used for biomass production. It is essential to obtain plant breeding tools, which can identify genotypes with improved drought tolerance and water use efficiency (WOE). In C-3 plant species, the variation in discrimination against C-13(Delta,13C) during photosynthesis has been shown to be a potential indicator for WOE, where discrimination against C-13 and WUE were negatively correlated. The aim of this study was to determine the variation in the discrimination against C-13 between species and cultivars of three perennial C-3 grasses (Dactylis glomerate (cocksfoot), Festuca arundinacea (tall fescue) and Phalaris arundinacea (reed canary grass)) and test the relationships between discrimination against C-13, season-long water use WUEB, shoot and root biomass production in plants grown under well-watered and water-limited conditions. The grasses were grown in the greenhouse and exposed to two irrigation regimes, which corresponded to 25% and 60% water holding capacity, respectively. We found negative relationships between discrimination against C-13 and WUEB and between discrimination against C-13 and shoot biomass production, under both the well-watered and water-limited growth conditions (p < 0.001). Discrimination against C-13 decreased in response to water limitation (p < 0.001). We found interspecific differences in the discrimination against C-13, WUEB, and shoot biomass production, where the cocksfoot cultivars showed lowest and the reed canary grass cultivars highest values of discrimination against C-13. Cocksfoot cultivars also showed highest WUEB, shoot biomass production and potential tolerance to water limitation. We conclude that discrimination against C-13 appears to be a useful indicator, when selecting C-3 grass crops for biomass production under drought conditions. (C) 2017 Elsevier Masson SAS. All rights reserved.
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16.
  • Dusi, Valentina, et al. (författare)
  • Involvement of the tomato BBX16 and BBX17 microProteins in reproductive development
  • 2024
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 213
  • Tidskriftsartikel (refereegranskat)abstract
    • BBXs are B-Box zinc finger proteins that can act as transcription factors and regulators of protein complexes. Several BBX proteins play important roles in plant development. Two Arabidopsis thaliana microProteins belonging to the BBX family, named miP1a and miP1b, homotypically interact with and modulate the activity of other BBX proteins, including CONSTANS, which transcriptionally activates the florigen, FLOWERING LOCUS T. Arabidopsis plants overexpressing miP1a and miP1b showed delayed flowering. In tomato, the closest homologs of miP1a and miP1b are the microProteins SlBBX16 and SlBBX17. This study was aimed at investigating whether the constitutive expression of SlBBX16/17 in Arabidopsis and tomato impacted reproductive development. The heterologous expression of the two tomato microProteins in Arabidopsis caused a delay in the flowering transition; however, the effect was weaker than that observed when the native miP1a/b were overexpressed. In tomato, overexpression of SlBBX17 prolonged the flowering period; this effect was accompanied by downregulation of the flowering inhibitors Self Pruning (SP) and SP5G. SlBBX16 and SlBBX17 can hetero-oligomerize with TCMP-2, a cystine-knot peptide involved in flowering pattern regulation and early fruit development in tomato. The increased expression of both microProteins also caused alterations in tomato fruit development: we observed in the case of SlBBX17 a decrease in the number and size of ripe fruits as compared to WT plants, while for SlBBX16, a delay in fruit production up to the breaker stage. These effects were associated with changes in the expression of GA-responsive genes.
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17.
  • Eckert, Diana, et al. (författare)
  • The maximum carboxylation rate of Rubisco affects CO2 refixation in temperate broadleaved forest trees
  • 2020
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 155, s. 330-337
  • Tidskriftsartikel (refereegranskat)abstract
    • Mesophyll resistance to CO2 diffusion (rm) and the maximum carboxylation rate of Rubisco (Vcmax) affect photosynthetic rates, and can potentially also influence the percentage of respiratory and photorespiratory CO2 being refixated (Pr) by mesophyll cells. Here we investigated how various leaf anatomical traits (e.g. leaf mass per area [LMA] and leaf dry matter content [LDMC]) influenced rm in leaves of mature forest trees. We further explored how rm and Vcmax in turn affected Pr, and if these traits varied among species and leaves along a light gradient. Photosynthetic CO2 response of leaves grown in high-, medium-, and low-light environments was measured, from Pinus sylvestris [Scots pine], Picea abies [Norway spruce], Quercus robur [English oak], and Betula pendula [Silver birch] in southern Sweden. A modified version of the Farquhar-von Caemmerer-Berry model was fitted to the leaf gas exchange data to estimate Vcmax, rm and Pr. We found that of all leaf traits measured, only LMA for Q. robur was significantly higher in leaves from high-light environments. When comparing species, both rm and LMA were significantly higher in the conifers, and rm had a negative correlation with Vcmax. We found that Pr was similar between different species and functional groups, with an average of 73.2% (and SD of ±10.4) across all species. There was a strong, positive correlation between Pr and Vcmax in broadleaves, and we hypothesise that this effect might derive from a higher CO2 drawdown near Rubisco in leaves with high Vcmax.
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18.
  • Edstam, Monika M., et al. (författare)
  • Characterization of GPI-anchored lipid transfer proteins in Physcomitrella patens
  • 2014
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 75, s. 55-69
  • Tidskriftsartikel (refereegranskat)abstract
    • The non-specific lipid transfer proteins (nsLTPs) are characterized by a compact structure with a central hydrophobic cavity very suitable for binding hydrophobic ligands, such as lipids. The nsLTPs are encoded by large gene families in all land plant lineages, but seem to be absent from green algae. The nsLTPs are classified to different types based on molecular weight, sequence similarity, intron position or spacing between the cysteine residues. The Type G nsLTPs (LTPGs) have a GPI-anchor in the C-terminal region which may attach the protein to the exterior side of the plasma membrane. Here, we present the first characterization of nsLTPs from an early diverged plant, the moss Physcomitrella patens. Physcomitrella LTPGs were heterologously produced and purified from Pichia pastoris. The purified moss LTPGs were found to be extremely heat stable and showed a binding preference for unsaturated fatty acids. Expression of a moss LTPG-YFP fusion revealed localization to the plasma membrane. The expression of many of the moss LTPGs were found to be upregulated during drought and cold treatments. Lipid profiling revealed that cutin monomers, such as C16 and C18 mono- and di-hydroxylated fatty acids, could be identified in Physcomitrella.
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19.
  • Foresi, Noelia, et al. (författare)
  • The tiny giant of the sea, Ostreococcus's unique adaptations
  • 2024
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 211
  • Forskningsöversikt (refereegranskat)abstract
    • Ostreococcus spp. are unicellular organisms with one of the simplest cellular organizations. The sequencing of the genomes of different Ostreococcus species has reinforced this status since Ostreococcus tauri has one most compact nuclear genomes among eukaryotic organisms. Despite this, it has retained a number of genes, setting it apart from other organisms with similar small genomes. Ostreococcus spp. feature a substantial number of selenocysteine-containing proteins, which, due to their higher catalytic activity compared to their selenium-lacking counterparts, may require a reduced quantity of proteins. Notably, O. tauri encodes several ammonium transporter genes, that may provide it with a competitive edge for acquiring nitrogen (N). This characteristic makes it an intriguing model for studying the efficient use of N in eukaryotes. Under conditions of low N availability, O. tauri utilizes N from abundant proteins or amino acids, such as L-arginine, similar to higher plants. However, the presence of a nitric oxide synthase (L-arg substrate) sheds light on a new metabolic pathway for L-arg in algae. The metabolic adaptations of O. tauri to day and night cycles offer valuable insights into carbon and iron metabolic configuration. O. tauri has evolved novel strategies to optimize iron uptake, lacking the classic components of the iron absorption mechanism. Overall, the cellular and genetic characteristics of Ostreococcus contribute to its evolutionary success, making it an excellent model for studying the physiological and genetic aspects of how green algae have adapted to the marine environment. Furthermore, given its potential for lipid accumulation and its marine habitat, it may represent a promising avenue for third-generation biofuels.
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20.
  • Fridborg, Ingela, et al. (författare)
  • Varied response of Spodoptera littoralis against Arabidopsis thaliana with metabolically engineered glucosinolate profiles
  • 2012
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 50, s. 72-78
  • Tidskriftsartikel (refereegranskat)abstract
    • Upon herbivory glucosinolates are known to be degraded into a cascade of secondary products that can be detrimental for certain herbivores. We performed herbivory bioassays using first and second instar generalist Lepidoptera larvae Spodoptera littoralis on Arabidopsis thaliana engineered to overexpress novel glucosinolates. A differential response in larval feeding patterns was observed on the plants engineered with novel glucosinolates. Larvae fed on plants overexpressing 4-hydroxybenzyl glucosinolate and isopropyl glucosinolate showed little response. Larvae fed on 35S:CYP79A2 plants engineered to overexpress benzyl glucosinolates, however, showed reduced larval and pupal weights. Upon herbivory a high expression of JA signalling gene LOX2 was observed on the 35S:CYP79A2 plants compared to the PR1a and VSP2 expression. To confirm the role of benzyl isothiocyanate (BITC), a degradation product of benzyl glucosinolate overexpressing plants, in the retarded larval growth we used Virus Induced Gene Silencing (VIGS) approach to silence LOX2 expression in the 35S:CYP79A2 plants. S. littoralis larvae fed on LOX2 silenced 35S:CYP79A2 plants exhibited a retarded larval growth thus indicating that BITC played a pivotal role in anti-herbivory and not only the JA signalling pathway. (C) 2011 Elsevier Masson SAS. All rights reserved.
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21.
  • Gadjieva, Rena, et al. (författare)
  • Analysis of gun phenotype in barley magnesium chelatase and Mg-protoporphyrin IX monomethyl ester cyclase mutants
  • 2005
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 43:10-11, s. 901-908
  • Tidskriftsartikel (refereegranskat)abstract
    • The ability of barley (Hordeum vulgare L.) chlorophyll biosynthetic mutants to regulate the expression of Lhc genes was analyzed by a microarray approach. The Lhc genes are located in the nucleus and encode chlorophyll a/b binding proteins of the light-harvesting complex. The chlorophyll a/b binding proteins are some of the many proteins, which are imported to the chloroplast. It has been suggested that the chloroplast can regulate expression of nuclear genes encoding chloroplast proteins, using a chlorophyll biosynthetic intermediate such as Mg-protoporphyrin IX (MP) or Mg-protoporphyrin IX monomethyl ester (MPE) as a signal molecule. These compounds are intermediates between the two enzymes magnesium-chelatase (EC 6.6.1.1) and Mg-protoporphyrin IX monomethyl ester cyclase (EC 1.14.13.81) in the chlorophyll biosynthetic pathway. Genomes uncoupled (gun) mutants are defective in the chloroplast-to-nucleus signal transduction and express Lhc even when chloroplast development is inhibited by the herbicide norflurazon. We show that barley xantha-f, -g and -h mutants, defective in the three Mg-chelatase genes, have a gun phenotype. In contrast, a xantha-l mutant, defective in a gene of Mg-protoporphyrin monomethyl ester cyclase did not. Genome uncoupling in the xantha-f, -g, -h and -l mutants was also analyzed in absence of norflurazon. All mutants showed transcription of Lhc. This was unexpected in the case of xantha-l as this mutant showed accumulation of MPE, which has been suggested to be one of the two negative regulators of Lhc transcription. We suggest that chlorophyll intermediates may only function as signal molecules at an early developmental stage of chloroplast development.
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22.
  • Gadjieva, Rena, et al. (författare)
  • Nonsense-mediated mRNA decay in barley mutants allows the cloning of mutated genes by a microarray approach.
  • 2004
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 42:7-8, s. 681-685
  • Tidskriftsartikel (refereegranskat)abstract
    • We have previously described a microarray approach to identify and clone genes from mutants of higher organisms. In the method cDNA of two mutants with similar phenotype are competitively hybridized to DNA clones arrayed on a glass slide. Clones corresponding to an mRNA that is not expressed in one of the strains due to a mutation will be specifically highlighted in the hybridization, which provides a possibility to identify and eventually clone the mutated gene. The approach is dependent on mutations that affect the amount of mRNA. Nonsense mutations, which prematurely terminate translation, can be such mutations as a surveillance system known as nonsense-mediated decay (NMD) has been developed by organisms to reduce the abundance of mRNA with nonsense codons. In the present study, we have analysed the barley (Hordeum vulgare L.) magnesium chelatase mutants xantha-f 26, xantha-f 27 and xantha-f 40 in order to investigate the presence of NMD in barley, as well as the importance of the position of the stop codon for NMD. Both nonsense-mutants xantha-f 27 and xantha-f 40, but not the missense mutant xantha-f 26, showed NMD. This was not expected for xantha-f 27 as its mutation is in the last exon of the gene. We conclude the NMD expands the number of mutants that can be used for gene cloning by our described microarray approach.
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23.
  • Gough, Simon, et al. (författare)
  • A new method for isolating physiologically active Mg-protoporphyrin
  • 2007
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 45:12, s. 932-936
  • Tidskriftsartikel (refereegranskat)abstract
    • Mg-protoporphyrin monomethyl ester (MPE) is a biosynthetic intermediate of chlorophyll and converted by MPE cyclase to protochlorophyllide. Limited availability of MPE has so far hampered cyclase research. In a new, simplified, method MPE was prepared from freeze dried bchE mutant Rhodobacter capsulatus DB575 cells by extraction with acetone/H2O/25% NH3. Isolated MPE was identified by absorption and fluorescence spectroscopy, and its purity was analyzed by HPLC. The extracted MPE was dried and redissolved in buffered DMSO and its substrate activity is shown by enzymatic cyclase assays. A linear time course was observed for MPE conversion to protochlorophyllide by enzymes from barley etioplasts. Our innovation of freeze drying the R. capsulatus cells before extraction provides a high yield method for MPE, which is significantly faster and more reproducible than previous extraction methods.
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24.
  • Greger, Maria, 1956-, et al. (författare)
  • Equisetum arvense as a silica fertilizer
  • 2024
  • Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 210
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim was to use the agricultural weed and silica (Si) hyperaccumulator Equisetum arvense as Si fertilizer in plant cultivation. We investigated (1) the Si uptake in various Equisetum species, (2) where Si accumulates in the Equisetum plant, (3) processing methods to release as much Si as possible from dried, ground E. arvense plants and (4) which treatment yields gives the highest uptake of Si in young wheat plants cultivated in soil containing ground E. arvense . The results showed that E. arvense containes 22% Si and was among the best Si accumulators. Equisetum arvense accumulates Si as both soluble and firmly bound fractions. Amorphous silica (SiO 2 ) accumulates in the outer cell walls of epidermis of the entire plant. Regarding the processing method, a longer treatment time, greater concentration of Equisetum , boiling, and the addition of sodium bicarbonate increased the Si availability in ground, dried E. arvense . The addition of untreated, ground, dried E. arvense to the soil, corresponding to 160 kg Si ha -1 , increased the available Si in the soil and the Si uptake in wheat plants by five -fold, compared with the control. Boiling the ground E. arvense increased the Si uptake by 10 times, and the of sodium bicarbonate increased the availability and uptake by 40 times, compared with the control. In conclusion, dried, ground E. arvense can be used as a Si fertilizer as is, after boiling for a slightly better effect, or with sodium bicarbonate (up to a similar amount as the ground material) for best effect.
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25.
  • Grimberg, Åsa (författare)
  • Preferred carbon precursors for lipid labelling in the heterotrophic endosperm of developing oat (Avena sativa L.) grains
  • 2014
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 83, s. 346-355
  • Tidskriftsartikel (refereegranskat)abstract
    • Oat (Avena sativa L.) is unusual among the cereal grains in storing high amounts of oil in the endosperm; up to 90% of total grain oil. By using oat as a model species for oil metabolism in the cereal endosperm, we can learn how to develop strategies to redirect carbon from starch to achieve high-oil yielding cereal crops. Carbon precursors for lipid synthesis were compared in two genetically close oat cultivars with different endosperm oil content (about 6% and 10% of grain dw, medium-oil; MO, and high-oil; HO cultivar, respectively) by supplying a variety of 14C-labelled substrates to the grain from both up- and downstream parts of glycolysis, either through detached oat panicles in vitro or by direct injection in planta. When supplied by direct injection, 14C from acetate was identified to label the lipid fraction of the grain to the highest extent among substrates tested; 46% of net accumulated 14C, demonstrating its applicability as a marker for lipids in the endosperm. Time course analyses of injected 14C acetate during grain development suggested a more efficient transfer of fatty acids from polar lipids to triacylglycerol in the HO as compared to the MO cultivar, and turnover of triacylglycerol was suggested to not play a major role for the final oil content of oat grain endosperm despite the low amount of protective oleosins in this tissue. Moreover, availability of light was shown to drastically affect grain net carbon accumulation from 14C-sucrose when supplied through detached panicles for the HO cultivar.
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26.
  • Igamberdiev, A U, et al. (författare)
  • Capacity for NADPH/NADP turnover in the cytosol of barley seed endosperm : The role of NADPH-dependent hydroxypyruvate reductase
  • 2000
  • Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 38:10, s. 747-753
  • Tidskriftsartikel (refereegranskat)abstract
    • Barley (Hordeum vulgare L.) endosperm from developing seeds was found to contain relatively high activities of cytosolic NAD(P)II-dependent hydroxypyruvate reductase (HPR-2) and isocitrate dehydrogenase (ICDH). In contrast, activities of peroxisomal NADH-dependent hydroxypyruvate reductase (HPR-1) and glycolate oxidase as well as cytosolic NAD(P)H-dependent glyoxylate reductase were very low or absent in the endosperm both during maturation and seed germination, indicating the lack of a complete glycolate cycle in this tissue. In addition, activities of cytosolic glucose-6-phosphate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase were low or absent in the endosperm. The endosperm HPR-2 exhibited similar properties to those of an earlier described HPR-2 from green leaves, e.g. activities with both hydroxypyruvate and glyoxylate, utilization of both NADPH and NADH as cofactors, and a strong uncompetitive inhibition by oxalate (K-i in the order of micromolar). In etiolated leaves, both HPR-1 and HPR-2 were present with the same activity as in green leaves, indicating that the lack of HPR-I in the endosperm is not a general feature of non-photosynthetic tissues. We conclude that the endosperm has considerable capacity for cytosolic NADP/NADPH cycling via HPR-2 and ICDH, the former being possibly involved in the utilization of a serine-derived carbon. (C) 2000 Editions scientifiques et medicales Elsevier SAS.
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27.
  • Igamberdiev, A U, et al. (författare)
  • Origins and metabolism of formate in higher plants
  • 1999
  • Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 37:7-8, s. 503-513
  • Forskningsöversikt (refereegranskat)abstract
    • Formate, a simple one-carbon compound, is readily metabolized in plant tissues. In greening potato tubers, similar to some procaryotes, formate is directly synthesized via a ferredoxin-dependent fixation of CO2, serving as the main precursor for carbon skeletons in biosynthetic pathways. In other plant species and tissues, formate appears as a side-product of photorespiration and of fermentation pathways, but possibly also as a product of direct CO2 reduction in chloroplasts. Formate metabolism is closely related to serine synthesis and to all subsequent reactions originating from serine. Formate may have a role in biosynthesis of numerous compounds, in energetic metabolism and in si,signal transduction pathways related to stress response. This review summarizes the current state of formate research, physiological/biochemical and molecular aspects. (C) Elsevier, Paris.
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28.
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29.
  • Javed, M. Tariq, et al. (författare)
  • Cellular proton dynamics in Elodea canadensis leaves induced by cadmium
  • 2014
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 77, s. 15-22
  • Tidskriftsartikel (refereegranskat)abstract
    • Our earlier investigations showed that Elodea canadensis shoots, grown in the presence of cadmium (Cd), caused basification of the surrounding medium. The present study was aimed to examine the proton dynamics of the apoplastic, cytosolic and vacuolar regions of E. canadensis leaves upon Cd exposure and to establish possible linkage between cellular pH changes and the medium basification. The changes in cytosolic calcium [Ca2+](cyt) was also investigated as the [Ca2+](cyt) and [pH](cyt) homeostasis are closely linked. The cellular H+ and Ca2+ concentrations were monitored by fluorescence microscopy and ion-specific fluorescent dyes. Cadmium concentration of leaf-cell walls was measured after plant cultivation at different fixed levels of starting pH. The protoplasts from E. canadensis leaves were isolated by use of a newly developed enzymatic method. Upon Cd addition, both cytosolic and vacuolar pH of leaf protoplasts increased with a concomitant rise in the cytosolic Ca2+ concentration. Time course studies revealed that changes in [Ca2+](cyt) and [PH](cyt) followed similar dynamics. Cadmium (0.5 mu M) exposure decreased the apoplastic pH by 0.85 units. The maximum cell wall bound Cd-contents were obtained in plants grown at low starting pH. It is concluded that Cd treatment causes apoplastic acidosis in E. canadensis leaves associated with enhanced Cd binding to the cell walls and, consequently, reduced Cd influx into the cytosol.
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30.
  • Kleczkowski, Leszek A, 1954- (författare)
  • A new player in the starch field
  • 2001
  • Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 39:9, s. 759-761
  • Tidskriftsartikel (refereegranskat)abstract
    • A possible role of a newly discovered ADP-glucose pyrophosphatase (AGPPase) is discussed in the context of starch synthesis. The enzyme hydrolyses ADP-glucose (starch precursor) and may potentially divert the flow of carbon from starch synthase, resulting in a 'futile cycle' when 'coupled' with ADP-glucose pyrophosphorylase. The activity of AGPPase is inversely related to starch yield in sink tissues, and may be prone to inhibition by Pi and certain other products of the starch pathway. The AGPPase likely belongs to a `nudix' family of enzymes that in animal tissues and yeast are known to regulate levels of activated sugars. Some strategies for future research are underlined. (C) 2001 Editions scientifiques et medicales Elsevier SAS.
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31.
  • Larsson, Kristina A. E., et al. (författare)
  • Differential regulation of 3-aminomethylindole/N-methyl-3-aminomethylindole N-methyltransferase and gramine in barley by both biotic and abiotic stress conditions
  • 2011
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 49:1, s. 96-102
  • Tidskriftsartikel (refereegranskat)abstract
    • The expression of NMT (3-aminomethylindole/N-methyl-3-aminomethylindole N-methyltransferase; EC 2.1.1.), involved in the biosynthesis of the indole alkaloid gramine, was investigated in aphid-infested barley (Hordeum vulgare L). NMT is induced by methyl jasmonate and it was hypothesized that the gene would be more strongly upregulated in aphid-resistant barley. We examined the effects of feeding by three aphid species; Russian wheat aphid (Diuraphis noxia Mordvilko), rose-grain aphid (Metopolophium dirhodum Walker) and bird cherry-oat aphid (Rhopalosiphum padi L.) on barley genotypes with varying resistance characteristics. The barley genotypes selected included the cultivar Libra, known to upregulate gramine after feeding by Schizaphis graminum. Infestation by R. padi and M. dirhodum resulted in higher NMT expression in the doubled haploid line 5172-28:4 (DH28:4), which has moderate resistance against R. padi, but not in other aphid barley combinations. None of the aphid plant combinations had however increased gramine, suggesting that aphid-induction of gramine is specific to S. graminum. The increased abundance of NMT transcript in aphid-infested DH28:4 did not lead to higher amounts of NMT protein or NMT enzyme activity, neither did 200 times upregulation of NMT transcript in cotyledons incubated with methyl jasmonate, illustrating that even large differences measured at transcript level may have no metabolic consequences. Drought stress or treatments with abscisic acid did lead to higher gramine concentrations in several barley cultivars, but without any concomitant increase of NMT transcripts. Thus, the regulation of the biosynthetic pathway to gramine at transcript and metabolite level diverges during two different stress conditions.
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32.
  • Li, Shaoshan, et al. (författare)
  • Anthocyanin accumulation and changes in CHS and PR-5 gene expression in Arabidopsis thaliana after removal of the inflorescence stem (decapitation)
  • 2005
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 43:6, s. 521-525
  • Tidskriftsartikel (refereegranskat)abstract
    • Anthocyanin accumulation occurs in rosette leaves of Arabidopsis thaliana within 8 days after removal of the inflorescence stem. Expression of stress-induced genes CHS and PR-5 was strongly up-regulated by stem removal, and was highest on day 4 after decapitation. These levels were 10 and 5 times higher than in the control, respectively. No obvious difference was found in expression of LHCB, MEB5.2, or PYROA genes following stem removal. We demonstrate that removing the inflorescence stem triggers events in Arabidopsis, including pigment accumulation and changes in gene expression of a subset of stress-induced genes, in a tissue distant from the wound site.
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33.
  • Mahawar, Lovely, et al. (författare)
  • Effect of copper oxide and zinc oxide nanoparticles on photosynthesis and physiology of Raphanus sativus L. under salinity stress
  • 2024
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 206
  • Tidskriftsartikel (refereegranskat)abstract
    • The study evaluates the impact of two metal oxide nanoparticles: copper oxide (CuO) and zinc oxide (ZnO) on the growth and physiology of Raphanus sativus L. (radish) under salinity stress. Fifteen days old seedlings of R. sativus were subjected to different concentrations of salt stress (0 mM, 150 mM, and 300 mM NaCl) alone and in interaction with 100 mgL−1 metal oxide nanoparticle treatments (CuO and ZnO NPs via foliar spray) for 15 days. The results confirmed the severe effects of salinity stress on the growth and physiology of radish plants by decreasing nutrient uptake, leaf area, and photosystems photochemistry and by increasing proline accumulation, anthocyanin, flavonoids content, and antioxidant enzyme activities which is directly linked to increased oxidative stress. The foliar application of CuO and ZnO NPs alleviated the adverse effects of salt stress on radish plants, as indicated by improving these attributes. Foliar spray of ZnO NPs was found efficient in improving the leaf area, photosynthetic electron transport rate, the PSII quantum yield, proton conductance and mineral content in radish plants under NaCl stress. Besides, ZnO NPs decreased the NaCl-induced oxidative stress by declining proline, anthocyanin, and flavonoids contents and enzymatic activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX) and guaiacol peroxidase (GOPX). Thus, our study revealed that ZnO NPs are more effective and have beneficial effects over CuO NPs in promoting growth and reducing the adverse effects of NaCl stress in radish plants.
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34.
  • Matic, Sandra, et al. (författare)
  • Sucrose synthase isoforms in cultured tobacco cells
  • 2004
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 42:4, s. 299-306
  • Tidskriftsartikel (refereegranskat)abstract
    • The plant enzyme sucrose synthase (SuSy; EC 2.4.1.13) catalyzes the reversible conversion of sucrose and UDP into UDP-glucose (UDP-Glc) and fructose. The enzyme exists in different isoforms and is both located in the cytosol, membrane-bound and associated to the actin cytoskeleton. We here investigate sucrose synthase from tobacco (Nicotiana tabacum L.) BY-2 heterotrophic cell suspensions. Two different isoforms of sucrose synthase SuSy1 and SuSy2, could be purified from cytosolic extracts of these cells using a combination of poly(ethylene glycol) (PEG) precipitation, gel filtration, ion-exchange chromatography and affinity chromatography. They were clearly distinct. both with regard to the binding to the ion-exchange column and with regard to their kinetic and regulatory properties. SuSy 1, the more abundant species, showed lower V-max and K-m for sucrose and UDP compared to the less abundant SuSy2. The activity of SuSy2 in the breakdown direction was stimulated by 60% by actin, in contrast to that of SuSy 1, which showed a 17% inhibition. An indication of interaction between SuSy I and actin was obtained by partitioning in aqueous Dextran-PEG two-phase systems. Furthermore, fructose 2,6-bisphosphate (F26BP) at micromolar concentrations stimulated SuSy2 in the presence of actin while SuSy I was strongly inhibited by fructose. Possible roles of these two isoforms in the sucrose turnover in BY-2 cells are discussed. (C) 2004 Elsevier SAS. All rights reserved.
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35.
  • Morgan, Sherif H., et al. (författare)
  • Leaf ion homeostasis and plasma membrane H+-ATPase activity in Vicia faba change after extra calcium and potassium supply under salinity
  • 2014
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 82, s. 244-253
  • Tidskriftsartikel (refereegranskat)abstract
    • Salt stress in plants impacts apoplastic ion activities and cytosolic ionic homeostasis. The ameliorating effects exerted by calcium or potassium on compartmentation of ions in leaves under salinity are not fully understood. To clarify how calcium or potassium supply could ameliorate ion homeostasis and ATPase activities under salinity, 5 mM CaSO4 or 10 mM K2SO4 were added with, or without, 100 mM NaCl for 7 d and 21 d to Vicia faba grown in hydroponics. The apoplastic pH was detected with Oregon Green dextran dye in intact second-uppermost leaves by microscopy-based ratio imaging. The cytosolic Ca2+, Na+, K+ activities and pH were detected in protoplasts loaded with the acetoxy methyl-esters of Fura-2, SBFI, PBFI and BCECF, respectively, using epi-fluorescence microscopy. Furthermore, total Ca2+, Na+, K+ concentrations and growth parameters were investigated. The ATPase hydrolyzing activity increased with time, but decreased after long salinity treatment. The activity largely increased in calcium-treated plants, but was depressed in potassium-treated plants after 7 d. The calcium supply increased Vmax, and the ATPase activity increased with salinity in a non-competitive way for 7 d and 21 d. The potassium supply instead decreased activity competitively with Na+, after 21 d of salinity, with different effects on Km and Vmax. The confirmed higher ATPase activity was related with apoplast acidification, cytosol alkalinization and low cytosolic [Na+], and thus, might be an explanation why extra calcium improved shoot and leaf growth.
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36.
  • Nazaralian, Sanam, et al. (författare)
  • Comparison of silicon nanoparticles and silicate treatments in fenugreek
  • 2017
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 115, s. 25-33
  • Tidskriftsartikel (refereegranskat)abstract
    • Silicon (Si) fertilization improves crop cultivation and is commonly added in the form of soluble silicates. However, most natural plant-available Si originates from plant formed amorphous SiO2 particles, phytoliths, similar to SiO2-nanoparticles (SiNP). In this work we, therefore, compared the effect by sodium silicate and that of SiNP on Si accumulation, activity of antioxidative stress enzymes catalase, peroxidase, superoxide dismutase, lignification of xylem cell walls and activity of phenylalanine ammonia-Iyase (PAL) as well as expression of genes for the putative silicon transporter (PST), defensive (Tfgd 1) and phosphoenolpyruvate carboxykinase (PEPCK) and protein in fenugreek (Trigonella foenum-graecum L) grown in hydroponics. The results showed that Si was taken up from both silicate and SiNP treatments and increasing sodium silicate addition increased the translocation of Si to the shoot, while this was not shown with increasing SiNP addition. The silicon transporter PST was upregulated at a greater level when sodium silicate was added compared with SiNP addition. There were no differences in effects between sodium silicate and SiNP treatments on the other parameters measured. Both treatments increased the uptake and accumulation of Si, xylem cell wall lignification, cell wall thickness, PAL activity and protein concentration in seedlings, while there was no effect on antioxidative enzyme activity. Tfgd 1 expression was strongly downregulated in leaves at Si addition. The similarity in effects by silicate and SiNP would be due to that SiNP releases silicate, which may be taken up, shown by a decrease in SiNP particle size with time in the medium.
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37.
  • Novak, Ondrej, et al. (författare)
  • Effect of light on growth and endogenous hormones in Chlorella minutissima (Trebouxiophyceae)
  • 2014
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 79, s. 66-76
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant growth regulators (PGRs) play an important role in mediating growth and stress responses in plants. Light influences PGRs concentrations in vascular plants. The effect of light on growth and endogenous PGR concentrations in microalgae was investigated in the present study. Chlorella minutissima MACC 360 was grown in 14:10 h light:dark (L:D), continuous dark (CD) and continuous dark with the addition of 5 g L-1 glucose (CD + G) for 48 h. Cultures were synchronized in the L:D cultures, increasing in size during the light period and dividing during the dark period. C minutissima cells did not increase in size or undergo cell division in CD cultures. In CD + G conditions, the cultures were no longer synchronized but did continue to increase in cell size and constantly underwent cell division although fewer cells divided than in the L:D cultures. Endogenous auxin and cytokinin concentrations increased and gibberellin concentrations decreased over time in the actively growing cultures (L:D and CD + G) but did not increase in the CD cultures. The largest increase in indole content was in the CD + G cultures while the L:D cultures had the largest cytokinin increase. Brassinosteroid concentrations decreased over time in all the cultures including those grown in CD conditions. Abscisic acid (ABA) concentrations were low and only increased in the CD cultures. These results show that endogenous PGRs were affected by the light regime and/or culture growth. (C) 2014 Elsevier Masson SAS. All rights reserved.
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38.
  • Ohlsson, Anna B., et al. (författare)
  • Increased metal tolerance in Salix by nicotinamide and nicotinic acid
  • 2008
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 46:7, s. 655-664
  • Tidskriftsartikel (refereegranskat)abstract
    • We have earlier shown that nicotinamide (NIC) and nicotinic acid (NiA) can induce defence-related metabolism in plant cells; e.g. increase the level of glutathione. Here we investigated if NIC and NiA could increase the metal tolerance in metal sensitive clones of Salix viminalis and whether this would be mediated via increased glutathione level. Salix clones, sensitive or tolerant to zinc (Zn), copper (Cu) and cadmium (Cd) were grown in the presence of heavy metals (Cd, Cu or Zn) or NIC and NiA as well as in combination. In addition, the influence of N-acetyl-cystein (NAC) and L-2-oxothiazolidine 4-carboxylate (OTC), stimulators of reduced glutathione (GSH) biosynthesis, and the glutathione biosynthesis inhibitor buthionine sulfoximine (BSO) was analysed. Tolerance was measured as effects on root and shoot dry weight, and the glutathione and metal concentrations in the tissues were analysed. Results showed that NIC and NiA decreased the toxic effects of Cd, Cu and Zn on growth significantly in sensitive clones, but also to some extent in tolerant clones. However, the glutathione level and metal concentration did not change by NIC or NiA addition. Treatment with NAC, OTC or BSO did not per se influence the sensitivity to Cd, although the glutathione level increased in the presence of NAC and OTC and decreased in response to BSO. The results suggest that NIC and NiA increased the defence against heavy metals but not via glutathione formation per se.
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39.
  • Olayide, Priscilla Olukola, et al. (författare)
  • Transcriptome and metabolome profiling identify factors potentially involved in pro-vitamin A accumulation in cassava landraces
  • 2023
  • Ingår i: Plant Physiology and Biochemistry. - 0981-9428 .- 1873-2690. ; 199
  • Tidskriftsartikel (refereegranskat)abstract
    • Cassava (Manihot esculenta Crantz) is a predominant food security crop in several developing countries. Its storage roots, rich in carbohydrate, are deficient in essential micronutrients, including provitamin A carotenoids.Increasing carotenoid content in cassava storage roots is important to reduce the incidence of vitamin A deficiency, a public health problem in sub-Saharan Africa. However, cassava improvement advances slowly, mainly due to limited information on the molecular factors influencing 13-carotene accumulation in cassava.To address this problem, we performed comparative transcriptomic and untargeted metabolic analyses of roots and leaves of eleven African cassava landraces ranging from white to deep yellow colour, to uncover regulators of carotenoid biosynthesis and accumulation with conserved function in yellow cassava roots.Sequence analysis confirmed the presence of a mutation, known to influence 13-carotene content, in PSY transcripts of deep yellow but not of pale yellow genotypes. We identified genes and metabolites with expression and accumulation levels significantly associated with 13-carotene content. Particularly an increased activity of the abscisic acid catabolism pathway together with a reduced amount of L-carnitine, may be related to the carot-enoid pathway flux, higher in yellow than in white storage roots. In fact, NCED_3.1 was specifically expressed at a lower level in all yellow genotypes suggesting that it could be a potential target for increasing carotenoid accumulation in cassava.These results expand the knowledge on metabolite compositions and molecular mechanisms influencing carotenoid biosynthesis and accumulation in cassava and provide novel information for biotechnological ap-plications and genetic improvement of cassava with high nutritional values.
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40.
  • Olsson, Ulf, et al. (författare)
  • Characterization of eight barley xantha-f mutants deficient in magnesium chelatase
  • 2004
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 42:6, s. 557-564
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnesium chelatase (EC 6.6.1.1) catalyses the insertion of magnesium into protoporphyrin IX, the first unique step of the chlorophyll biosynthetic pathway. The enzyme is composed of three different subunits of approximately 40, 70 and 140 kDa. In barley (Hordeum vulgare L.) the subunits are encoded by the genes Xantha-h, Xantha-g and Xantha-f. In the 1950s, eight induced xantha-f mutants were isolated. In this work we characterized these mutations at the DNA level and provided explanations for their phenotypes. The xantha-f10 mutation is a 3 bp deletion, resulting in a polypeptide lacking the glutamate residue at position 424. The leaky mutation xantha-f26 has a missense mutation leading to a M632R exchange. The xantha-f27 and -f40 are deletions of 14 and 2 bp, respectively, resulting in truncated polypeptides of 1104 and 899 amino acid residues, respectively. Mutation xantha-f41 is an in-frame deletion that removes A439, L440, Q441 and V442 from the resulting protein. Mutation xantha-f58 is most likely a deletion of the whole Xantha-f gene, as no DNA fragments could be detected by PCR or southern blot experiments. The slightly leaky xantha-f60 and non-leaky -f68 mutations each have a missense mutation causing a P393L and G794E exchange in the polypeptide, respectively.
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41.
  • Oquist, Gunnar, 1941-, et al. (författare)
  • THE TEMPERATURE-DEPENDENCE OF THE REDOX STATE OF Q(A) AND SUSCEPTIBILITY OF PHOTOSYNTHESIS TO PHOTOINHIBITION
  • 1993
  • Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 31:5, s. 683-691
  • Tidskriftsartikel (refereegranskat)abstract
    • The relationship between the redox state of primary, stable quinone acceptor of photosystem II (Q(A)) and the susceptibility of photosynthesis to photoinhibition at different temperatures was investigated. Non-hardened and cold-hardened seedlings of winter rye, and of winter and spring cultivars of wheat, were obtained by growth at either 20/16-degrees-C (day/night) or 5/5-degrees-C (day/night), respectively. A single, curvi-linear relationship was established between the steady-state redox level Of Q(A) and the susceptibility of photosynthesis to short-term (8 h) photoinhibition at 5 or 25-degrees-C when spring and winter cultivars of rye and wheat, in non-hardened or cold-hardened states, were plotted together. Furthermore, irrespective of temperature (0 to 25-degrees-C) or state of cold-hardiness, the susceptibility of photosynthesis to photoinhibition was controlled fully in winter rye by the redox state Of Q(A); e.g. similar susceptibilities to photoinhibition were obtained at 0, 5 and 25-degrees-C provided that the photon fluence rate at the different temperatures was adjusted to keep 50% of the photosystem II reaction centres in a closed state under steady-state illumination. Our results suggest that the primary reason plants become prone to photoinhibition at low temperatures is that the proportion of closed reaction centres increases due to the low temperature imposed constraints on photosynthesis. Thus, we propose that low temperature sensitized photoinhibition results from low temperature inhibition of photosynthesis rather than from low temperature inhibition of the photosystem II repair cycle.
  •  
42.
  • Ristilä, Mikael, et al. (författare)
  • The role of the pyridoxine (vitamin B6) biosynthesis enzyme PDX1 in ultraviolet-B radiation responses in plants
  • 2011
  • Ingår i: Plant physiology and biochemistry (Paris). - Amsterdam : Elsevier. - 0981-9428 .- 1873-2690. ; 49:3, s. 284-292
  • Tidskriftsartikel (refereegranskat)abstract
    • Ultraviolet-B radiation regulates plant growth and morphology at low and ambient fluence rates but can severely impact on plants at higher doses. Some plant UV-B responses are related to the formation of reactive oxygen species (ROS) and pyridoxine (vitamin B6) has been reported to be a quencher of ROS. UV-B irradiation of Arabidopsis Col-0 plants resulted in increased levels of PDX1 protein, compared with UV-A-exposed plants. This was shown by immunoblot analysis using specific polyclonal antibodies raised against the recombinant PDX1.3 protein and confirmed by mass spectrometry analysis of immunoprecipitated PDX1. The protein was located mainly in the cytosol but also to a small extent in the membrane fraction of plant leaves. Immunohistochemical analysis performed in pea revealed that PDX1 is present in UV-B-exposed leaf mesophyll and palisade parenchyma but not in epidermal cells. Pyridoxine production increased in Col-0 plants exposed to 3 days of UV-B, whereas in an Arabidopsis pdx1.3 mutant UV-B did not induce pyridoxine biosynthesis. In gene expression studies performed after UV-B exposure, the pdx1.3 mutant showed elevated transcript levels for the LHCB1*3 gene (encoding a chlorophyll a/b-binding protein of the photosystem II light-harvesting antenna complex) and the pathogenesis-related protein 5 (PR-5) gene, compared with wild type.
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43.
  • Rodriguez-Calzada, Tania, et al. (författare)
  • Effect of UV-B radiation on morphology, phenolic compound production, gene expression, and subsequent drought stress responses in chili pepper (Capsicum annuum L.)
  • 2019
  • Ingår i: Plant physiology and biochemistry (Paris). - Paris, France : Elsevier. - 0981-9428 .- 1873-2690. ; 134, s. 94-102
  • Tidskriftsartikel (refereegranskat)abstract
    • It has been suggested that accumulation of flavonoids could be a key step in development of plant tolerance to different environmental stresses. Moreover, it has been recognized that abiotic stresses such as drought and UV-B radiation (280-315 nm) induce phenolic compound accumulation, suggesting a role for these compounds in drought tolerance. The aim of the present study was to evaluate the effect of UV-B exposure on chili pepper (Capsicum annuum, cv. ‘Coronel’) plant performance, phenolic compound production, and gene expression associated with response to subsequent drought stress. Additionally, the phenotypic response to drought stress of these plants was studied. UV-B induced a reduction both in stem length, stem dry weight and number of floral primordia. The largest reduction in these variables was observed when combining UV-B and drought. UV-B-treated well-watered plants displayed fructification approximately 1 week earlier than non-UV-B-treated controls. Flavonoids measured epidermally in leaves significantly increased during UV-B treatment. Specifically, UV-B radiation significantly increased chlorogenic acid and apigenin 8-C-hexoside levels in leaves and a synergistic increase of luteolin 6-C-pentoside-8-C-hexoside was obtained by UV-B and subsequent drought stress. Gene expression of phenylalanine ammonia lyase (PAL) and chalcone synthase (CHS) genes also increased during UV-B treatments. On the other hand, expression of genes related to an oxidative response, such as mitochondrial Mn-superoxide dismutase (Mn-SOD) and peroxidase (POD) was not induced by UV-B. Drought stress in UV-B-treated plants induced mitochondrial Mn-SOD gene expression. Taken together, the UV-B treatment did not induce significant tolerance in plants towards drought stress under the conditions used.
  •  
44.
  • Rozpadek, Piotr, et al. (författare)
  • Arbuscular mycorrhiza improves yield and nutritional properties of onion (Allium cepa)
  • 2016
  • Ingår i: Plant physiology and biochemistry (Paris). - Paris, France : Elsevier. - 0981-9428 .- 1873-2690. ; 107, s. 264-272
  • Tidskriftsartikel (refereegranskat)abstract
    • Improving the nutritional value of commonly cultivated crops is one of the most pending problems for modern agriculture. In natural environments plants associate with a multitude of fungal microorganisms that improve plant fitness. The best described group are arbuscular mycorrhizal fungi (AMF). These fungi have been previously shown to improve the quality and yield of several common crops. In this study we tested the potential utilization of Rhizophagus irregularis in accelerating growth and increasing the content of important dietary phytochemicals in onion (Allium cepa). Our results clearly indicate that biomass production, the abundance of vitamin B1 and its analogs and organic acid concentration can be improved by inoculating the plant with AM fungi. We have shown that improved growth is accompanied with up-regulated electron transport in PSII and antioxidant enzyme activity.
  •  
45.
  •  
46.
  • Sharma, Arti, et al. (författare)
  • Comprehensive analysis of plant rapid alkalization factor (RALF) genes
  • 2016
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 106, s. 82-90
  • Tidskriftsartikel (refereegranskat)abstract
    • Receptor mediated signal carriers play a critical role in the regulation of plant defense and development. Rapid alkalization factor (RALF) proteins potentially comprise important signaling components which may have a key role in plant biology. The RALF gene family contains large number of genes in several plant species, however, only a few RALF genes have been characterized to date. In this study, an extensive database search identified 39, 43, 34 and 18 RALF genes in Arabidopsis, rice, maize and soybean, respectively. These RALF genes were found to be highly conserved across the 4 plant species. A comprehensive analysis including the chromosomal location, gene structure, subcellular location, conserved motifs, protein structure, protein-ligand interaction and promoter analysis was performed. RALF genes from four plant species were divided into 7 groups based on phylogenetic analysis. In silico expression analysis of these genes, using microarray and EST data, revealed that these genes exhibit a variety of expression patterns. Furthermore, RALF genes showed distinct expression patterns of transcript accumulation in vivo following nitrosative and oxidative stresses in Arabidopsis. Predicted interaction between RALF and heme ligand also showed that RALF proteins may contribute towards transporting or scavenging oxygen moieties. This suggests a possible role for RALF genes during changes in cellular redox status. Collectively, our data provides a valuable resource to prime future research in the role of RALF genes in plant growth and development.
  •  
47.
  • Siedlecka, A, et al. (författare)
  • Primary carbon metabolism in Phaseolus vulgaris plants under Cd/Fe interaction
  • 1997
  • Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 35:12, s. 951-957
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of the Cd/Fe interaction on primary carbon metabolism in Phaseolus vulgaris L. cv. Slowianka plants was investigated. It was documented earlier that Cd induced a decrease in the leaf Fe content, and increased levels of Fe may reduce Cd toxicity. The aim of the present study was to check whether Cd is toxic to Calvin cycle enzymes and especially if different Fe levels can modify the Cd effect. Bush-bean seedlings were cultivated in the presence of different Cd concentrations (0, 10, 20, 50 mu M) and at different Fe doses (deficient: 0 mmol, normal: 0.25 mmol, excessive: 0.5 mmol). Leaf content of ATP, ADP, Calvin cycle metabolites, activity of RUBISCO and carbonic anhydrase were measured. The influence of Cd/Fe interaction on the content of Calvin cycle metabolites seemed to be of both direct and indirect nature. The Cd-induced increase in ATP content, and in the ATP/ADP ratio, resulted from a decreased ATP consumption. At a higher Fe dose, the Cd/Fe interaction resulted in a revitalisation of the adenylate pool and Calvin cycle metabolites. The inhibition of RUBISCO carboxylase activity may be considered as the primary plant response to Cd-stress. The mechanisms of RUBISCO activation operate to overcome this limitation, although their efficiency was decreased by high Cd concentrations, resulting in decreased RUBISCO activity. At a low Cd concentration, the increase in RUBISCO activity was correlated with increased carbonic anhydrase activity.
  •  
48.
  • Sivan, Pramod, 1984-, et al. (författare)
  • Immunolocalization of β-(1–4)-D-galactan, xyloglucans and xylans in the reaction xylem fibres of Leucaena leucocephala (Lam.) de Wit
  • 2019
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier. - 0981-9428 .- 1873-2690. ; 142, s. 217-223
  • Tidskriftsartikel (refereegranskat)abstract
    • Cell wall architecture of tension wood fibres represents a suitable biological system to study the mechanism of growth and maintenance of posture of trees growing under various physical and physiological growth constraints. In the present study, we investigated the spatial distributions of β-(1–4)-D-galactan, xyloglucan and xylans (both less and highly substituted) in the opposite and tension wood fibres of bent Leucaena leucocephala by immunolabelling with monoclonal antibodies LM5, CCRCM1, LM10 and LM11 specific to these carbohydrate epitopes. The presence of non-lignified, tertiary wall layer is the typical tension wood characteristic associated with the reaction xylem fibres in Leucaena. LM5 labelling of opposite fibres showed weak labelling in the cell walls indicating less concentration of β-(1–4)-D-galactans while tension wood showed strong labelling in the tertiary wall layer suggesting the gelatinous layer (G-layer) has a strong cross linking with β-(1–4)-D-galactans. Xyloglucan distribution was more in the compound middle lamellae and the primary wall-S1 layer boundary of tension wood fibres as compared to that of opposite wood. A weak labelling was also evident near the boundary between the G-layer and the secondary wall of tension wood fibres. The secondary wall of opposite and tension wood fibres showed a strong distribution of both ls ACG Xs (LM10) and hs ACG Xs (LM11) while a weak labelling was noticed in the compound middle lamella. Tension wood fibres also showed strong xylan labelling mainly confined to the lignified secondary walls while the G-layer showed weak xylan labelling. In conclusion, our results suggest that β-(1–4)-D-galactans and xyloglucans could be implicated in the tensile stress generation within the G-layer of tension wood fibres of Leucaena leucocephala.
  •  
49.
  • Steccanella, Verdiana, et al. (författare)
  • Linking chlorophyll biosynthesis to a dynamic plastoquinone pool.
  • 2015
  • Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 97, s. 207-216
  • Tidskriftsartikel (refereegranskat)abstract
    • Chlorophylls are essential cofactors in photosynthesis. All steps in the chlorophyll pathway are well characterized except for the cyclase reaction in which the fifth ring of the chlorophyll molecule is formed during conversion of Mg-protoporphyrin IX monomethyl ester into Protochlorophyllide. The only subunit of the cyclase identified so far, is AcsF (Xantha-l in barley and Chl27 in Arabidopsis). This subunit contains a typical consensus di-iron-binding sequence and belongs to a subgroup of di-iron proteins, such as the plastid terminal oxidase (PTOX) in the chloroplast and the alternative oxidase (AOX) found in mitochondria. In order to complete the catalytic cycle, the irons of these proteins need to be reduced from Fe(3+) to Fe(2+) and either a reductase or another form of reductant is required. It has been reported that the alternative oxidase (AOX) and the plastid terminal oxidase (PTOX) utilize the di-iron center to oxidise ubiquinol and plastoquinol, respectively. In this paper, we have used a specific inhibitor of di-iron proteins as well as Arabidopsis and barley mutants affected in regulation of photosynthetic electron flow, to show that the cyclase step indeed is directly coupled to the plastoquinone pool. Thus, plastoquinol might act as an electron donor for the cyclase reaction and thereby fulfil the role of a cyclase reductase. That would provide a functional connection between the redox status of the thylakoids and the biosynthesis of chlorophyll.
  •  
50.
  • Sävenstrand, Helena, et al. (författare)
  • Six genes strongly regulated by mercury in Pisum sativum roots
  • 2004
  • Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 42:2, s. 135-142
  • Tidskriftsartikel (refereegranskat)abstract
    • Suppression subtractive hybridisation was used to isolate heavy metal-induced genes from Pisum sativum roots hydroponically exposed to 5 microM HgCl2 and 10 microM EDTA. Six genes were induced out of which one, PsHMIP6B, was novel. The other genes (PsSAMT, PsI2'H, PsNDA, PsAPSR, PsPOD) had not previously been isolated from pea and sequenced. All six genes were also induced after exposure to 5 microM HgCl2 in the absence of EDTA. The induction pattern was in some cases different for the two Hg species, demonstrating a quicker response to-free Hg2+ than Hg-EDTA. The stress-specificity of the gene regulation was investigated by hydroponically adding 5 microM Cd2+. Most Hg-induced cDNAs were also induced by Cd2+ but to a smaller extent than after Hg exposure. In addition, the gene expression was also probed for tissue specificity, which showed that all six genes were expressed in roots and not in leaves.
  •  
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