| 1. |
- Lundberg, Peter, et al.
(författare)
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Phosphorus-31 and Nitrogen- 14 NMR Studies of the Uptake of Phosphorus and Nitrogen Compounds in the Marine Macroalgae Ulva lactuca
- 1989
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 89:4, s. 1380-1387
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Tidskriftsartikel (refereegranskat)abstract
- Cytoplasmic phosphomonoesters and inorganic phosphate, as well as vacuolar inorganic phosphate and polyphosphates, gave rise to the major peaks in (31)P nuclear magnetic resonance (NMR) spectra of the marine macroalgae Enteromorpha sp., Ceramium sp., and Ulva lactuca which were collected from the sea. In contrast, NMR-visible polyphosphates were lacking in Pylaiella sp. and intracellular vacuolar phosphate seemed to act as the main phosphorus store in this organism. In laboratory experiments, polyphosphates decreased in growing U. lactuca which was cultivated in continuous light under phosphate-deficient conditions. In contrast, the same organism cultivated in seawater with added phosphate and ammonium, accumulated phosphate mainly in the form of polyphosphates. When nitrate was provided as the only nitrogen source, accumulation of polyphosphates in the algae decreased with increasing external nitrate concentration. From the chemical shift of the cytoplasmic Pi peak, the cytoplasmic pH of superfused preparations of Ulva was estimated at 7.2. The vacuolar pH, determined from the chemical shifts of the vacuolar Pi and the terminal polyphosphate peaks, was between 5.5 and 6.0. The intracellular nitrate and ammonium levels in U. lactuca were determined by (14)N NMR. Both nitrogen sources were taken up and stored intracellularly; however, the uptake of ammonium was much faster than that of nitrate.
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| 2. |
- Adam, Zach, et al.
(författare)
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Chloroplast and mitochondrial proteases in Arabidopsis : a proposed nomenclature
- 2001
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 125:4, s. 1912-1918
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Tidskriftsartikel (refereegranskat)abstract
- The identity and scope of chloroplast and mitochondrial proteases in higher plants has only started to become apparent in recent years. Biochemical and molecular studies suggested the existence of Clp, FtsH, and DegP proteases in chloroplasts, and a Lon protease in mitochondria, although currently the full extent of their role in organellar biogenesis and function remains poorly understood. Rapidly accumulating DNA sequence data, especially from Arabidopsis, has revealed that these proteolytic enzymes are found in plant cells in multiple isomeric forms. As a consequence, a systematic approach was taken to catalog all these isomers, to predict their intracellular location and putative processing sites, and to propose a standard nomenclature to avoid confusion and facilitate scientific communication. For the Clp protease most of the ClpP isomers are found in chloroplasts, whereas one is mitochondrial. Of the ATPase subunits, the one ClpD and two ClpC isomers are located in chloroplasts, whereas both ClpX isomers are present in mitochondria. Isomers of the Lon protease are predicted in both compartments, as are the different forms of FtsH protease. DegP, the least characterized protease in plant cells, has the most number of isomers and they are predicted to localize in several cell compartments. These predictions, along with the proposed nomenclature, will serve as a framework for future studies of all four families of proteases and their individual isomers.
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| 3. |
- Adolfsson, Lisa, 1984, et al.
(författare)
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Enhanced Secondary- and Hormone Metabolism in Leaves of Arbuscular Mycorrhizal Medicago truncatula.
- 2017
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Ingår i: Plant physiology. - : Oxford University Press (OUP). - 1532-2548 .- 0032-0889. ; 175:1, s. 392-411
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Tidskriftsartikel (refereegranskat)abstract
- Arbuscular mycorrhizas (AM) are the most common symbiotic associations between a plant's root compartment and fungi. They provide nutritional benefit (mostly inorganic phosphate [Pi]), leading to improved growth, and nonnutritional benefits, including defense responses to environmental cues throughout the host plant, which, in return, delivers carbohydrates to the symbiont. However, how transcriptional and metabolic changes occurring in leaves of AM plants differ from those induced by Pi fertilization is poorly understood. We investigated systemic changes in the leaves of mycorrhized Medicago truncatula in conditions with no improved Pi status and compared them with those induced by high-Pi treatment in nonmycorrhized plants. Microarray-based genome-wide profiling indicated up-regulation by mycorrhization of genes involved in flavonoid, terpenoid, jasmonic acid (JA), and abscisic acid (ABA) biosynthesis as well as enhanced expression of MYC2, the master regulator of JA-dependent responses. Accordingly, total anthocyanins and flavonoids increased, and most flavonoid species were enriched in AM leaves. Both the AM and Pi treatments corepressed iron homeostasis genes, resulting in lower levels of available iron in leaves. In addition, higher levels of cytokinins were found in leaves of AM- and Pi-treated plants, whereas the level of ABA was increased specifically in AM leaves. Foliar treatment of nonmycorrhized plants with either ABA or JA induced the up-regulation of MYC2, but only JA also induced the up-regulation of flavonoid and terpenoid biosynthetic genes. Based on these results, we propose that mycorrhization and Pi fertilization share cytokinin-mediated improved shoot growth, whereas enhanced ABA biosynthesis and JA-regulated flavonoid and terpenoid biosynthesis in leaves are specific to mycorrhization.
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| 4. |
- Andersson, Annica, et al.
(författare)
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Down-Regulation of the CSLF6 Gene Results in Decreased (1,3;1,4)-beta-D-Glucan in Endosperm of Wheat
- 2010
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 152, s. 1209-1218
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Tidskriftsartikel (refereegranskat)abstract
- (1,3; 1,4)-beta-D-Glucan (beta-glucan) accounts for 20% of the total cell walls in the starchy endosperm of wheat (Triticum aestivum) and is an important source of dietary fiber for human nutrition with potential health benefits. Bioinformatic and array analyses of gene expression profiles in developing caryopses identified the CELLULOSE SYNTHASE-LIKE F6 (CSLF6) gene as encoding a putative beta-glucan synthase. RNA interference constructs were therefore designed to down-regulate CSLF6 gene expression and expressed in transgenic wheat under the control of a starchy endosperm-specific HMW subunit gene promoter. Analysis of wholemeal flours using an enzyme-based kit and by high-performance anion-exchange chromatography after digestion with lichenase showed decreases in total beta-glucan of between 30% and 52% and between 36% and 53%, respectively, in five transgenic lines compared to three control lines. The content of water-extractable beta-glucan was also reduced by about 50% in the transgenic lines, and the M-r distribution of the fraction was decreased from an average of 79 to 85 X 10(4) g/mol in the controls and 36 to 57 x 10(4) g/mol in the transgenics. Immunolocalization of beta-glucan in semithin sections of mature and developing grains confirmed that the impact of the transgene was confined to the starchy endosperm with little or no effect on the aleurone or outer layers of the grain. The results confirm that the CSLF6 gene of wheat encodes a b-glucan synthase and indicate that transgenic manipulation can be used to enhance the health benefits of wheat products.
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| 5. |
- Andersson, Björn, 1985, et al.
(författare)
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The Fluctuating Cell-Specific Light Environment and Its Effects on Cyanobacterial Physiology
- 2019
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Ingår i: Plant physiology. - : Oxford University Press (OUP). - 1532-2548 .- 0032-0889. ; 181:2, s. 547-564
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 American Society of Plant Biologists. All Rights Reserved. Individual cells of cyanobacteria or algae are supplied with light in a highly irregular fashion when grown in industrial-scale photobioreactors (PBRs). These conditions coincide with significant reductions in growth rate compared to the static light environments commonly used in laboratory experiments. We grew a dense culture of the model cyanobacterium Synechocystis sp. PCC 6803 under a sinusoidal light regime in a bench-top PBR (the Phenometrics environmental PBR [ePBR]). We developed a computational fluid dynamics model of the ePBR, which predicted that individual cells experienced rapid fluctuations (∼6 s) between 2,000 and <1 µmol photons m-2 s-1, caused by vertical mixing and self-shading. The daily average light exposure of a single cell was 180 µmol photons m-2 s-1 Physiological measurements across the day showed no in situ occurrence of nonphotochemical quenching, and there was no significant photoinhibition. An ex situ experiment showed that up to 50% of electrons derived from PSII were diverted to alternative electron transport in a rapidly changing light environment modeled after the ePBR. Collectively, our results suggest that modification of nonphotochemical quenching may not increase cyanobacterial productivity in PBRs with rapidly changing light. Instead, tuning the rate of alternative electron transport and increasing the processing rates of electrons downstream of PSI are potential avenues to enhance productivity. The approach presented here could be used as a template to investigate the photophysiology of any aquatic photoautotroph in a natural or industrially relevant mixing regime.
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| 6. |
- Andersson, Mariette
(författare)
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A Specialized Diacylglycerol Acyltransferase Contributes to the Extreme Medium-Chain Fatty Acid Content of Cuphea Seed Oil
- 2017
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 174, s. 97-109
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Tidskriftsartikel (refereegranskat)abstract
- Seed oils of many Cuphea sp. contain.90% of medium-chain fatty acids, such as decanoic acid (10: 0). These seed oils, which are among the most compositionally variant in the plant kingdom, arise from specialized fatty acid biosynthetic enzymes and specialized acyltransferases. These include lysophosphatidic acid acyltransferases (LPAT) and diacylglycerol acyltransferases (DGAT) that are required for successive acylation of medium-chain fatty acids in the sn-2 and sn-3 positions of seed triacylglycerols (TAGs). Here we report the identification of a cDNA for a DGAT1-type enzyme, designated CpuDGAT1, from the transcriptome of C. avigera var pulcherrima developing seeds. Microsomes of camelina (Camelina sativa) seeds engineered for CpuDGAT1 expression displayed DGAT activity with 10:0-CoA and the diacylglycerol didecanoyl, that was approximately 4-fold higher than that in camelina seed microsomes lacking CpuDGAT1. In addition, coexpression in camelina seeds of CpuDGAT1 with a C. viscosissima FatB thioesterase (CvFatB1) that generates 10:0 resulted in TAGs with nearly 15 mol % of 10: 0. More strikingly, expression of CpuDGAT1 and CvFatB1 with the previously described CvLPAT2, a 10:0-CoA-specific Cuphea LPAT, increased 10:0 amounts to 25 mol % in camelina seed TAG. These TAGs contained up to 40 mol % 10:0 in the sn-2 position, nearly double the amounts obtained from coexpression of CvFatB1 and CvLPAT2 alone. Although enriched in diacylglycerol, 10:0 was not detected in phosphatidylcholine in these seeds. These findings are consistent with channeling of 10:0 into TAG through the combined activities of specialized LPAT and DGAT activities and demonstrate the biotechnological use of these enzymes to generate 10:0-rich seed oils.
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| 7. |
- Andersson, Mariette
(författare)
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Comparative Transcriptome Analysis of Three Oil Palm Fruit and Seed Tissues That Differ in Oil Content and Fatty Acid Composition
- 2013
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 162, s. 1337-1358
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Tidskriftsartikel (refereegranskat)abstract
- Oil palm (Elaeis guineensis) produces two oils of major economic importance, commonly referred to as palm oil and palm kernel oil, extracted from the mesocarp and the endosperm, respectively. While lauric acid predominates in endosperm oil, the major fatty acids (FAs) of mesocarp oil are palmitic and oleic acids. The oil palm embryo also stores oil, which contains a significant proportion of linoleic acid. In addition, the three tissues display high variation for oil content at maturity. To gain insight into the mechanisms that govern such differences in oil content and FA composition, tissue transcriptome and lipid composition were compared during development. The contribution of the cytosolic and plastidial glycolytic routes differed markedly between the mesocarp and seed tissues, but transcriptional patterns of genes involved in the conversion of sucrose to pyruvate were not related to variations for oil content. Accumulation of lauric acid relied on the dramatic up-regulation of a specialized acyl-acyl carrier protein thioesterase paralog and the concerted recruitment of specific isoforms of triacylglycerol assembly enzymes. Three paralogs of the WRINKLED1 (WRI1) transcription factor were identified, of which EgWRI1-1 and EgWRI1-2 were massively transcribed during oil deposition in the mesocarp and the endosperm, respectively. None of the three WRI1 paralogs were detected in the embryo. The transcription level of FA synthesis genes correlated with the amount of WRI1 transcripts and oil content. Changes in triacylglycerol content and FA composition of Nicotiana benthamiana leaves infiltrated with various combinations of WRI1 and FatB paralogs from oil palm validated functions inferred from transcriptome analysis.
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| 8. |
- Andersson, Mats X., 1977, et al.
(författare)
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Chloroplast biogenesis. Regulation of lipid transport to the thylakoid in chloroplasts isolated from expanding and fully expanded leaves of pea.
- 2001
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Ingår i: Plant physiology. - 0032-0889. ; 127:1, s. 184-93
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Tidskriftsartikel (refereegranskat)abstract
- To study the regulation of lipid transport from the chloroplast envelope to the thylakoid, intact chloroplasts, isolated from fully expanded or still-expanding pea (Pisum sativum) leaves, were incubated with radiolabeled lipid precursors and thylakoid membranes subsequently were isolated. Incubation with UDP[(3)H]Gal labeled monogalactosyldiacylglycerol in both envelope membranes and digalactosyldiacylglycerol in the outer chloroplast envelope. Galactolipid synthesis increased with incubation temperature. Transport to the thylakoid was slow below 12 degrees C, and exhibited a temperature dependency closely resembling that for the previously reported appearance and disappearance of vesicles in the stroma (D.J. Morré, G. Selldén, C. Sundqvist, A.S. Sandelius [1991] Plant Physiol 97: 1558-1564). In mature chloroplasts, monogalactosyldiacylglycerol transport to the thylakoid was up to three times higher than digalactosyldiacylglycerol transport, whereas the difference was markedly lower in developing chloroplasts. Incubation of chloroplasts with [(14)C]acyl-coenzyme A labeled phosphatidylcholine (PC) and free fatty acids in the inner envelope membrane and phosphatidylglycerol at the chloroplast surface. PC and phosphatidylglycerol were preferentially transported to the thylakoid. Analysis of lipid composition revealed that the thylakoid contained approximately 20% of the chloroplast PC. Our results demonstrate that lipids synthesized at the chloroplast surface as well as in the inner envelope membrane are transported to the thylakoid and that lipid sorting is involved in the process. Furthermore, the results also indicate that more than one pathway exists for galactolipid transfer from the chloroplast envelope to the thylakoid.
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| 9. |
- Andersson, Mats X., 1977, et al.
(författare)
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Involvement of the Electrophilic Isothiocyanate Sulforaphane in Arabidopsis Local Defense Responses
- 2015
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 167:1
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Tidskriftsartikel (refereegranskat)abstract
- Plants defend themselves against microbial pathogens through a range of highly sophisticated and integrated molecular systems. Recognition of pathogen-secreted effector proteins often triggers the hypersensitive response (HR), a complex multicellular defense reaction where programmed cell death of cells surrounding the primary site of infection is a prominent feature. Even though the HR was described almost a century ago, cell-to-cell factors acting at the local level generating the full defense reaction have remained obscure. In this study, we sought to identify diffusible molecules produced during the HR that could induce cell death in naive tissue. We found that 4-methylsulfinylbutyl isothiocyanate (sulforaphane) is released by Arabidopsis (Arabidopsis thaliana) leaf tissue undergoing the HR and that this compound induces cell death as well as primes defense in naive tissue. Two different mutants impaired in the pathogen-induced accumulation of sulforaphane displayed attenuated programmed cell death upon bacterial and oomycete effector recognition as well as decreased resistance to several isolates of the plant pathogen Hyaloperonospora arabidopsidis. Treatment with sulforaphane provided protection against a virulent H. arabidopsidis isolate. Glucosinolate breakdown products are recognized as antifeeding compounds toward insects and recently also as intracellular signaling and bacteriostatic molecules in Arabidopsis. The data presented here indicate that these compounds also trigger local defense responses in Arabidopsis tissue.
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| 10. |
- Annacondia López, María Luz, et al.
(författare)
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Parasitic plant small RNA analyses unveil parasite-specific signatures of microRNA retention, loss, and gain
- 2022
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548.
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Tidskriftsartikel (refereegranskat)abstract
- Parasitism is a successful life strategy that has evolved independently in several families of vascular plants. The genera Cuscuta and Orobanche represent examples of the two profoundly different groups of parasites: one parasitizing host shoots and the other infecting host roots. In this study, we sequenced and described the overall repertoire of small RNAs from Cuscuta campestris and Orobanche aegyptiaca. We showed that C. campestris contains a number of novel microRNAs (miRNAs) in addition to a conspicuous retention of miRNAs that are typically lacking in other Solanales, while several typically conserved miRNAs seem to have become obsolete in the parasite. One new miRNA appears to be derived from a horizontal gene transfer event. The exploratory analysis of the miRNA population (exploratory due to the absence of a full genomic sequence for reference) from the root parasitic O. aegyptiaca also revealed a loss of a number of miRNAs compared to photosynthetic species from the same order. In summary, our study shows partly similar evolutionary signatures in the RNA silencing machinery in both parasites. Our data bear proof for the dynamism of this regulatory mechanism in parasitic plants.MicroRNAs in parasitic plants reflect their lifestyle.
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