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- Igamberdiev, Abir U, et al.
(författare)
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Photorespiration Contributes to Stomatal Regulation and Carbon Isotope Fractionation: A Study with Barley, Potato and Arabidopsis Plants Deficient in Glycine Decarboxylase
- 2004
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Ingår i: Photosynthesis Research. ; 81, s. 139-152
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Tidskriftsartikel (refereegranskat)abstract
- The rates of respiration in light and darkness, C i/C a and carbon isotope fractionation were investigated in glycine decarboxylase-deficient plants of barley, potato and Arabidopsis thaliana grown in climate chambers with controlled light intensity, temperature, humidity, irradiation and different CO2 concentrations (360, 700 and 1400 µl l–1) and compared to the wild-type plants. All photorespiration-impaired plants exhibited higher C i/C a and corresponding lower apparent water-use efficiencies, which were more expressed under high irradiance and elevated temperature. The mutants were depleted in 13C as compared to the wild-type plants, with a difference of up to 6permil following growth in 360 µl l–1 CO2. We determined the carbon isotope content at different CO2 concentrations to calculate the contribution of both C i/C a and photorespiration for 13C/12C fractionation. The direct effect of photorespiration was in the range of 0.7–1.0permil, from which we calculated the value of fractionation at the site of glycine decarboxylation as being 10–13permil, which is in agreement with the previously reported carbon isotope discrimination exerted by the glycine decarboxylase. Respiratory rates, particularly in the light, were increased in the glycine decarboxylase mutants. The necessity of the maintenance of a high CO2 concentration near the site of carboxylation in chloroplasts in plants deficient in photorespiratory enzymes, requires an increased opening of the stomata with a corresponding decrease in water-use efficiency. It is concluded that photorespiration participates in the regulation of C i/C a and contributes to carbon isotope fractionation, both via effects on stomata and via discrimination of 13C in the glycine decarboxylase reaction.
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| 4. |
- Baba, Kyoko, et al.
(författare)
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Organellar gene transcription and early seedling development are affected in the rpoT;2 mutant of Arabidopsis.
- 2004
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Ingår i: Plant J. - 0960-7412. ; 38:1, s. 38-48
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Tidskriftsartikel (refereegranskat)abstract
- An Arabidopsis mutant that exhibited reduced root length was isolated from a population of activation-tagged T-DNA insertion lines in a screen for aberrant root growth. This mutant also exhibited reduced hypocotyl length as well as a delay in greening and altered leaf shape. Molecular genetic analysis of the mutant indicated a single T-DNA insertion in the gene RpoT;2 encoding a homolog of the phage-type RNA polymerase (RNAP), that is targeted to both mitochondria and plastids. A second T-DNA-tagged allele also showed a similar phenotype. The mutation in RpoT;2 affected the light-induced accumulation of several plastid mRNAs and proteins and resulted in a lower photosynthetic efficiency. In contrast to the alterations in the plastid gene expression, no major effect of the rpoT;2 mutation on the accumulation of examined mitochondrial gene transcripts and proteins was observed. The rpoT;2 mutant exhibited tissue-specific alterations in the transcript levels of two other organelle-directed nuclear-encoded RNAPs, RpoT;1 and RpoT;3. This suggests the existence of cross-talk between the regulatory pathways of the three RNAPs through organelle to nucleus communication. These data provide an important information on a role of RpoT;2 in plastid gene expression and early plant development.
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| 6. |
- Bergman, Anders, et al.
(författare)
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Method to Obtain a Chlorophyll-free Preparation of Intact Mitochondria from Spinach Leaves.
- 1980
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Ingår i: Plant Physiology. - Rockville, USA : AMER SOC PLANT PHYSIOLOGISTS. - 0032-0889 .- 1532-2548. ; 66:3, s. 442-445
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondria from green leaves of spinach have been prepared using a three-step procedure involving differential centrifugation, partition in an aqueous dextran polyethylene glycol two-phase system and Percoll gradient centrifugation. The mitochondrial fractions after the different steps of purification were compared. The final mitochondrial preparation was totally free from chloroplast material measured as chlorophyll content. The enrichment of mitochondria in relation to peroxisomes and microsomes was approximately 12 and 33 times, respectively, based on NAD:isocitrate dehydrogenase activity, glycolate oxidase activity, and NADPH:cytochrome c oxidoreductase activity. The apparent intactness of the inner and the outer mitochondrial membranes was higher than 90% as measured by latency of enzyme activities. The mitochondria showed high respiratory rates with respiratory control and the ADP/O ratios approached the theoretical limits.
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| 7. |
- Bhalerao, Rupali, et al.
(författare)
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Gene expression in autumn leaves
- 2003
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 131:2, s. 430-442
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Tidskriftsartikel (refereegranskat)abstract
- Two cDNA libraries were prepared, one from leaves of a field-grown aspen (Populus tremula) tree, harvested just before any visible sign of leaf senescence in the autumn, and one from young but fully expanded leaves of greenhouse-grown aspen (Populus tremula X tremuloides). Expressed sequence tags (ESTs; 5,128 and 4,841, respectively) were obtained from the two libraries. A semiautomatic method of annotation and functional classification of the ESTs, according to a modified Munich Institute of Protein Sequences classification scheme, was developed, utilizing information from three different databases. The patterns of gene expression in the two libraries were strikingly different. In the autumn leaf library, ESTs encoding metallothionein, early light-inducible proteins, and cysteine proteases were most abundant. Clones encoding other proteases and proteins involved in respiration and breakdown of lipids and pigments, as well as stress-related genes, were also well represented. We identified homologs to many known senescence-associated genes, as well as seven different genes encoding cysteine proteases, two encoding aspartic proteases, five encoding metallothioneins, and 35 additional genes that were up-regulated in autumn leaves. We also indirectly estimated the rate of plastid protein synthesis in the autumn leaves to be less that 10% of that in young leaves.
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| 8. |
- BORODIN, V, et al.
(författare)
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THE EFFECT OF LIGHT QUALITY ON THE INDUCTION OF EFFICIENT PHOTOSYNTHESIS UNDER LOW CO2 CONDITIONS IN CHLAMYDOMONAS-REINHARDTII AND CHLORELLA-PYRENOIDOSA
- 1994
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Ingår i: Physiologia Plantarum. - 0031-9317 .- 1399-3054. ; 92:2, s. 254-260
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Tidskriftsartikel (refereegranskat)abstract
- The effect of blue and red light on the adaptation to low CO2 conditions was studied in high-CO2 grown cultures of Chlorella pyrenoidosa (82T) and Chlamydomonas reinhardtii (137(+)) by measuring O-2 exchange under various inorganic carbon (C-i) concentrations. At equal photosynthetic photon flux density (PPFD), blue light was more favourable for adaptation in both species, compared to red light. The difference in photosynthetic oxygen evolution between cells adapted to low C-i under blue and red light was more pronounced when oxygen evolution was measured under low C-i compared to high C-i conditions. The effect of light quality on adaptation remained for several hours. The different effects caused by blue and red light was observed in C. pyrenoidosa over a wide range of PPFD with increasing differences at increasing PPFD. The maximal difference was obtained at a PPFD above 1 500 mu mol m(-2) s(-1). We found no difference in the extracellular carbonic anhydrase activity between blue- and red light adapted cells. The light quality effect recorded under C-i-limiting conditions in C. reinhardtii cells adapted to air, was only 37% less when instead of pure blue light red light containing 12.5% of blue light (similar PPFD as blue light) was used during adaptation to low carbon. This indicates that in addition to affecting photosynthesis, blue light affected a sensory system involved in algal adaptation to low C-i conditions. Since the affinity for C-i of C. pyrenoidosa and C. reinhardtii cells adapted to air under blue light was higher than that of cells adapted under red light, we suggest that induction of some component(s) of the C-i accumulating mechanism is regulated by the light quality.
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| 9. |
- Borysiuk, Klaudia, et al.
(författare)
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Glyoxalase I activity affects Arabidopsis sensitivity to ammonium nutrition
- 2022
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Ingår i: Plant Cell Reports. - : Springer. - 0721-7714 .- 1432-203X. ; 41, s. 2393-2413
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Tidskriftsartikel (refereegranskat)abstract
- Key message: Elevated methylglyoxal levels contribute to ammonium-induced growth disorders in Arabidopsis thaliana. Methylglyoxal detoxification pathway limitation, mainly the glyoxalase I activity, leads to enhanced sensitivity of plants to ammonium nutrition.Abstract: Ammonium applied to plants as the exclusive source of nitrogen often triggers multiple phenotypic effects, with severe growth inhibition being the most prominent symptom. Glycolytic flux increase, leading to overproduction of its toxic by-product methylglyoxal (MG), is one of the major metabolic consequences of long-term ammonium nutrition. This study aimed to evaluate the influence of MG metabolism on ammonium-dependent growth restriction in Arabidopsis thaliana plants. As the level of MG in plant cells is maintained by the glyoxalase (GLX) system, we analyzed MG-related metabolism in plants with a dysfunctional glyoxalase pathway. We report that MG detoxification, based on glutathione-dependent glyoxalases, is crucial for plants exposed to ammonium nutrition, and its essential role in ammonium sensitivity relays on glyoxalase I (GLXI) activity. Our results indicated that the accumulation of MG-derived advanced glycation end products significantly contributes to the incidence of ammonium toxicity symptoms. Using A. thaliana frostbite1 as a model plant that overcomes growth repression on ammonium, we have shown that its resistance to enhanced MG levels is based on increased GLXI activity and tolerance to elevated MG-derived advanced glycation end-product (MAGE) levels. Furthermore, our results show that glyoxalase pathway activity strongly affects cellular antioxidative systems. Under stress conditions, the disruption of the MG detoxification pathway limits the functioning of antioxidant defense. However, under optimal growth conditions, a defect in the MG detoxification route results in the activation of antioxidative systems.
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