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1.
  • Alexandersson, Erik, et al. (författare)
  • Arabidopsis Plasma Membrane Proteomics Identifies Components of Transport, Signal Transduction and Membrane Trafficking
  • 2004
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 45:11, s. 1543-1556
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to identify integral proteins and peripheral proteins associated with the plasma membrane, highly purified Arabidopsis plasma membranes from green tissue (leaves and petioles) were analyzed by mass spectrometry. Plasma membranes were isolated by aqueous two-phase partitioning, which yields plasma membrane vesicles with a cytoplasmic-side-in orientation and with a purity of 95%. These vesicles were turned inside-out by treatment with Brij 58 to remove soluble contaminating proteins enclosed in the vesicles and to remove loosely bound contaminating proteins. In total, 238 putative plasma membrane proteins were identified, of which 114 are predicted to have transmembrane domains or to be glycosyl phosphatidylinositol anchored. About two-thirds of the identified integral proteins have not previously been shown to be plasma membrane proteins. Of the 238 identified proteins, 76% could be classified according to function. Major classes are proteins involved in transport (17%), signal transduction (16%), membrane trafficking (9%) and stress responses (9%). Almost a quarter of the proteins identified in the present study are functionally unclassified and more than half of these are predicted to be integral.
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2.
  • Alm Rosenblad, Magnus, 1957, et al. (författare)
  • Identification of chloroplast signal recognition particle RNA genes.
  • 2004
  • Ingår i: Plant & cell physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 45:11, s. 1633-9
  • Tidskriftsartikel (refereegranskat)abstract
    • The signal recognition particle (SRP) is a ribonucleoprotein complex responsible for targeting proteins to the ER membrane in eukaryotes, the plasma membrane in bacteria and the thylakoid membrane in chloroplasts. In higher plants two different SRP-dependent mechanisms have been identified: one post-translational for proteins imported to the chloroplast and one co-translational for proteins encoded by the plastid genome. The post-translational chloroplast SRP (cpSRP) consists of the protein subunits cpSRP54 and cpSRP43. An RNA component has not been identified and does not seem to be required for the post-translational cpSRP. The co-translational mechanism is known to involve cpSRP54, but an RNA component has not yet been identified. Several chloroplast genomes have been sequenced recently, making a phylogenetically broad computational search for cpSRP RNA possible. We have analysed chloroplast genomes from 27 organisms. In higher plant chloroplasts, no SRP RNA genes were identified. However, eight plastids from red algae and Chlorophyta were found to contain an SRP RNA gene. These results suggest that SRP RNA forms a complex in these plastids with cpSRP54, reminiscent of the eubacterial SRP.
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3.
  • Alsterfjord, Magnus, et al. (författare)
  • Plasma membrane H+-ATPase and 14-3-3 Isoforms of Arabidopsis leaves: Evidence for isoform specificity in the 14-3-3/H+-ATPase interaction
  • 2004
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 45:9, s. 1202-1210
  • Tidskriftsartikel (refereegranskat)abstract
    • The plasma membrane H+-ATPase is activated by binding of 14-3-3 protein to the phosphorylated C terminus. Considering the large number of 14-3-3 and H+-ATPase isoforms in Arabidopsis (13 and 11 expressed genes, respectively), specificity in binding may exist between 14-3-3 and H+-ATPase isoforms. We now show that the H'-ATPase is the main target for 14-3-3 binding at the plasma membrane, and that all twelve 14-3-3 istiforms tested bind to the H+-ATPase in vitro. Using specific antibodies for nine of the 14-3-3 isoforms, we show that GF14epsilon, mu, lambda, omega, chi, phi, nu, and upsilon are present in leaves, but that isolated plasma membranes lack GF14chi, phi and upsilon. Northern blots using isoform-specific probes for all 14-3-3 and H+-ATPase isoforms showed that transcripts were present for most of the isoforms. Based on mRNA levels, GF14epsilon, mu, lambda and chi are highly expressed 14-3-3 isoforms, and AHA1, 3, and 11 highly expressed H+-ATPase isoforms in leaves. However, mass peptide fingerprinting identified AHA1 and 2 with the highest score, and their presence could be confirmed by MS/MS. It may be calculated that under 'unstressed' conditions less than one percent of total 14-3-3 is attached to the H+-ATPase. However, during a condition requiring full activation of H+ pumping, as induced here by the presence of the fungal toxin fusicoccin, several percent of total 14-3-3 may be engaged in activation of the H+-ATPase.
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4.
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5.
  • Bolte, Susanne, et al. (författare)
  • Distinct Lytic Vacuolar Compartments are Embedded Inside the Protein Storage Vacuole of Dry and Germinating Arabidopsis thaliana Seeds
  • 2011
  • Ingår i: PLANT AND CELL PHYSIOLOGY. - 0032-0781. ; 52:7, s. 1142-1152
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant cell vacuoles are diverse and dynamic structures. In particular, during seed germination, the protein storage vacuoles are rapidly replaced by a central lytic vacuole enabling rapid elongation of embryo cells. In this study, we investigate the dynamic remodeling of vacuolar compartments during Arabidopsis seed germination using immunocytochemistry with antibodies against tonoplast intrinsic protein (TIP) isoforms as well as proteins involved in nutrient mobilization and vacuolar acidification. Our results confirm the existence of a lytic compartment embedded in the protein storage vacuole of dry seeds, decorated by gamma-TIP, the vacuolar proton pumping pyrophosphatase (V-PPase) and the metal transporter NRAMP4. They further indicate that this compartment disappears after stratification. It is then replaced by a newly formed lytic compartment, labeled by gamma-TIP and V-PPase but not AtNRAMP4, which occupies a larger volume as germination progresses. Altogether, our results indicate the successive occurrence of two different lytic compartments in the protein storage vacuoles of germinating Arabidopsis cells. We propose that the first one corresponds to globoids specialized in mineral storage and the second one is at the origin of the central lytic vacuole in these cells.
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6.
  • Christensen, Anna, et al. (författare)
  • Functional characterization of Arabidopsis calreticulin1a : a key alleviator of endoplasmic reticulum stress
  • 2008
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press. - 0032-0781 .- 1471-9053. ; 49:6, s. 912-924
  • Tidskriftsartikel (refereegranskat)abstract
    • The chaperone calreticulin plays important roles in a variety of processes in the endoplasmic reticulum (ER) of animal cells, such as Ca2+ signaling and protein folding. Although the functions of calreticulin are well characterized in animals, only indirect evidence is available for plants. To increase our understanding of plant calreticulins we introduced one of the Arabidopsis isoforms, AtCRT1a, into calreticulin-deficient (crt–/–) mouse embryonic fibroblasts. As a result of calreticulin deficiency, the mouse crt–/– fibroblasts have decreased levels of Ca2+ in the ER and impaired protein folding abilities. Expression of the AtCRT1a in mouse crt–/– fibroblasts rescued these phenotypes, i.e. AtCRT1a restored the Ca2+-holding capacity and chaperone functions in the ER of the mouse crt–/– fibroblasts, demonstrating that the animal sorting machinery was also functional for a plant protein, and that basic calreticulin functions are conserved across the Kingdoms. Expression analyses using a β-glucuronidase (GUS)–AtCRT1a promoter construct revealed high expression of CRT1a in root tips, floral tissues and in association with vascular bundles. To assess the impact of AtCRT1a in planta, we generated Atcrt1a mutant plants. The Atcrt1a mutants exhibited increased sensitivity to the drug tunicamycin, an inducer of the unfolded protein response. We therefore conclude that AtCRT1a is an alleviator of the tunicamycin-induced unfolded protein response, and propose that the use of the mouse crt–/– fibroblasts as a calreticulin expression system may prove useful to assess functionalities of calreticulins from different species.
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7.
  • Curien, Gilles, et al. (författare)
  • The Water to Water Cycles in Microalgae.
  • 2016
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 57:7, s. 1354-1363
  • Tidskriftsartikel (refereegranskat)abstract
    • In oxygenic photosynthesis, light produces ATP plus NADPH via linear electron transfer, i.e. the in-series activity of the two photosystems: PSI and PSII. This process, however, is thought not to be sufficient to provide enough ATP per NADPH for carbon assimilation in the Calvin-Benson-Bassham cycle. Thus, it is assumed that additional ATP can be generated by alternative electron pathways. These circuits produce an electrochemical proton gradient without NADPH synthesis, and, although they often represent a small proportion of the linear electron flow, they could have a huge importance in optimizing CO2 assimilation. In Viridiplantae, there is a consensus that alternative electron flow comprises cyclic electron flow around PSI and the water to water cycles. The latter processes include photosynthetic O2 reduction via the Mehler reaction at PSI, the plastoquinone terminal oxidase downstream of PSII, photorespiration (the oxygenase activity of Rubisco) and the export of reducing equivalents towards the mitochondrial oxidases, through the malate shuttle. In this review, we summarize current knowledge about the role of the water to water cycles in photosynthesis, with a special focus on their occurrence and physiological roles in microalgae.
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8.
  • Ekelund, Nils, 1956-, et al. (författare)
  • Photomovement and photobleaching in two Gyrodinium species
  • 1988
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 29, s. 1109-1114
  • Tidskriftsartikel (refereegranskat)abstract
    • The phototactic orientation in Gyrodinium dorsum and G. aureolum has been analyzed. Both species show only positive phototaxis with an optimum at about 300 W-m–2. The mechanism of photoorientation does not seem to be based on a dichroic orientation of the photoreceptor pigments as in the flagellate Euglena gracilis. Photobleaching experiments have shown a far higher resistance toward continuous irradiation at even high fluence rates than in other flagellates which is in good agreement with the exclusive behavior of positive phototaxis.
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9.
  • Fernandez-Santos, R, et al. (författare)
  • Protein Profiles of Lipid Droplets during the Hypersensitive Defense Response of Arabidopsis against Pseudomonas Infection
  • 2020
  • Ingår i: Plant & cell physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 61:6, s. 1144-1157
  • Tidskriftsartikel (refereegranskat)abstract
    • Lipid droplets (LDs) have classically been viewed as seed storage particles, yet they are now emerging as dynamic organelles associated with developmental and stress responses. Nevertheless, their involvement in plant immunity has still been little studied. Here, we found LD accumulation in Arabidopsis thaliana leaves that induced a hypersensitive response (HR) after Pseudomonas infection. We established a protocol to reproducibly isolate LDs and to analyze their protein content. The expression of GFP fusion proteins in Nicotiana benthamiana and in transgenic Arabidopsis lines validated the LD localization of glycerol-3-phosphate acyltransferase 4 (GPAT4) and 8 (GPAT8), required for cutin biosynthesis. Similarly, we showed LD localization of α-dioxygenase1 (α-DOX1) and caleosin3 (CLO3), involved in the synthesis of fatty acid derivatives, and that of phytoalexin-deficient 3 (PAD3), which is involved in camalexin synthesis. We found evidence suggesting the existence of different populations of LDs, with varying protein contents and distributions. GPAT4 and GPAT8 were associated with LDs inside stomata and surrounding cells of untreated leaves, yet they were mainly confined to LDs in guard cells after bacterial inoculation. By contrast, α-DOX1 and PAD3 were associated with LDs in the epidermal cells of HR-responding leaves, with PAD3 mostly restricted to cells near dead tissue, while CLO3 had a more ubiquitous distribution. As such, the nature of the proteins identified, together with the phenotypic examination of selected mutants, suggests that LDs participate in lipid changes and in the production and transport of defense components affecting the interaction of plants with invading pathogens.
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10.
  • Garcia Cerdan, Jose Gines, 1977-, et al. (författare)
  • Antisense inhibition of the PsbX protein affects PSII integrity in the higher plant Arabidopsis Thaliana
  • 2009
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press. - 0032-0781 .- 1471-9053. ; 50:2, s. 191-202
  • Tidskriftsartikel (refereegranskat)abstract
    • PSII, the oxygen-evolving complex of photosynthetic organisms, contains an intriguingly large number of low molecular weight proteins. PsbX, one of these proteins, is ubiquitous in PSII complexes of cyanobacteria and plants. In previous studies, deletion of the PsbX protein in cyanobacteria has not resulted in clear phenotypic changes. Here we report the construction of an antisense (AS-PsbX) line in Arabidopsis thaliana with <10% of wild-type PsbX levels. AS-PsbX plants are capable of photoautotrophic growth, but biochemical, biophysical and immunological evidence demonstrates that reduction of PsbX contents leads to reduced levels of functional assembled PSII core complexes, while the light-harvesting antennae are not affected. In addition, levels of phosphorylation of the core proteins D1, D2 and CP43 are severely reduced in the antisense plants relative to their wild-type counterparts. We conclude that PsbX is important for accumulation of functional PSII.
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11.
  • Gendre, Delphine, et al. (författare)
  • Cell Wall Polysaccharides are Mislocalized to the Vacuole in echidna Mutants
  • 2013
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 54, s. 1867-1880
  • Tidskriftsartikel (refereegranskat)abstract
    • During cell wall biosynthesis, the Golgi apparatus is the platform for cell wall matrix biosynthesis and the site of packaging, of both matrix polysaccharides and proteins, into secretory vesicles with the correct targeting information. The objective of this study was to dissect the post-Golgi trafficking of cell wall polysaccharides using echidna as a vesicle traffic mutant of Arabidopsis thaliana and the pectin-secreting cells of the seed coat as a model system. ECHIDNA encodes a trans-Golgi network (TGN)-localized protein, which was previously shown to be required for proper structure and function of the secretory pathway. In echidna mutants, some cell wall matrix polysaccharides accumulate inside cells, rather than being secreted to the apoplast. In this study, live cell imaging of fluorescent protein markers as well as transmission electron microscopy (TEM)/immunoTEM of cryofixed seed coat cells were used to examine the consequences of TGN disorganization in echidna mutants under conditions of high polysaccharide production and secretion. While in wild-type seed coat cells, pectin is secreted to the apical surface, in echidna, polysaccharides accumulate in post-Golgi vesicles, the central lytic vacuole and endoplasmic reticulum-derived bodies. In contrast, proteins were partially mistargeted to internal multilamellar membranes in echidna. These results suggest that while secretion of both cell wall polysaccharides and proteins at the TGN requires ECHIDNA, different vesicle trafficking components may mediate downstream events in their secretion from the TGN.
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12.
  • Granlund, Irene, et al. (författare)
  • The TL29 protein is lumen located, associated with PSII and not an ascorbate peroxidase
  • 2009
  • Ingår i: Plant and Cell Physiology. - : Oxford Journals. - 0032-0781 .- 1471-9053. ; 50:11, s. 1898-1910
  • Tidskriftsartikel (refereegranskat)abstract
    • The TL29 protein is one of the more abundant proteins in the thylakoid lumen of plant chloroplasts. Based on its sequence homology to ascorbate peroxidases, but without any supporting biochemical evidence, TL29 was suggested to be involved in the plant defense system against reactive oxygen species and consequently renamed to APX4. Our in vivo and in vitro analyses failed to show any peroxidase activity associated with TL29; it bound neither heme nor ascorbate. Recombinant overexpressed TL29 had no ascorbate-dependent peroxidase activity, and various mutational analyses aiming to convert TL29 into an ascorbate peroxidase failed. Furthermore, in the thylakoid lumen no such activity could be associated with TL29 and, additionally, TL29 knock-out mutants did not show any decreased peroxidase activity or increased content of radical oxygen species when grown under light stress. Instead we could show that TL29 is a lumen-located component associated with PSII.
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13.
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14.
  • Han, Xue-Min, et al. (författare)
  • Evolution and Function of the Populus SABATH Family Reveal That a Single Amino Acid Change Results in a Substrate Switch
  • 2018
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press. - 0032-0781 .- 1471-9053. ; 59:2, s. 392-403
  • Tidskriftsartikel (refereegranskat)abstract
    • Evolutionary mechanisms of substrate specificities of enzyme families remain poorly understood. Plant SABATH methyltransferases catalyze methylation of the carboxyl group of various low molecular weight metabolites. Investigation of the functional diversification of the SABATH family in plants could shed light on the evolution of substrate specificities in this enzyme family. Previous studies identified 28 SABATH genes from the Populus trichocarpa genome. In this study, we re-annotated the Populus SABATH gene family, and performed molecular evolution, gene expression and biochemical analyses of this large gene family. Twenty-eight Populus SABATH genes were divided into three classes with distinct divergences in their gene structure, expression responses to abiotic stressors and enzymatic properties of encoded proteins. Populus class I SABATH proteins converted IAA to methyl-IAA, class II SABATH proteins converted benzoic acid (BA) and salicylic acid (SA) to methyl-BA and methyl-SA, while class III SABATH proteins converted farnesoic acid (FA) to methyl-FA. For Populus class II SABATH proteins, both forward and reverse mutagenesis studies showed that a single amino acid switch between PtSABATH4 and PtSABATH24 resulted in substrate switch. Our findings provide new insights into the evolution of substrate specificities of enzyme families.
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15.
  • He, Hanzi, et al. (författare)
  • Effects of Parental Temperature and Nitrate on Seed Performance are Reflected by Partly Overlapping Genetic and Metabolic Pathways
  • 2016
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press. - 0032-0781 .- 1471-9053. ; 57:3, s. 473-487
  • Tidskriftsartikel (refereegranskat)abstract
    • Seed performance is affected by the seed maturation environment and previously, we have shown that temperature, nitrate and light intensity were the most influential environmental factors affecting seed performance. Seeds developed in these environments were selected to assess the underlying metabolic pathways, using a combination of transcriptomics and metabolomics. These analyses revealed that the effects of the temperature and nitrate parental environments were reflected by partly overlapping genetic and metabolic networks, as indicated by similar changes in metabolites and transcripts expression levels. Nitrogen-metabolism related metabolites (asparagine, GABA and allantoin) were significantly decreased in both low temperature (15°C) and low nitrate (N0) maturation environments. Correspondingly, nitrogen-metabolism genes (ALLANTOINASE, NITRATE REDUCTASE 1, NITRITE REDUCTASE 1 and NITRILASE 4) were differentially regulated in the low temperature and nitrate maturation environments, as compared with control conditions. High light intensity during seed maturation increased galactinol content, and displayed a high correlation with seed longevity. Low light had a genotype-specific effect on cell surface encoding genes in the DELAY OF GERMINATION 6-Near Isogenic Line (NILDOG6). Overall, the integration of phenotypes, metabolites and transcripts led to new insights in the regulation of seed performance.
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16.
  • Hüdig, M., et al. (författare)
  • Plants Possess a Cyclic Mitochondrial Metabolic Pathway similar to the Mammalian Metabolic Repair Mechanism Involving Malate Dehydrogenase and l-2-Hydroxyglutarate Dehydrogenase
  • 2014
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 56:9, s. 1820-1830
  • Tidskriftsartikel (refereegranskat)abstract
    • Enzymatic side reactions can give rise to the formation of wasteful and toxic products that are removed by metabolite repair pathways. In this work, we identify and characterize a mitochondrial metabolic repair mechanism in Arabidopsis thaliana involving malate dehydrogenase (mMDH) and l-2-hydroxyglutarate dehydrogenase (l-2HGDH). We analyze the kinetic properties of both A. thaliana mMDH isoforms, and show that they produce l-2-hydroxyglutarate (l-2HG) from 2-ketoglutarate (2-KG) at low rates in side reactions. We identify A. thaliana l-2HGDH as a mitochondrial FAD-containing oxidase that converts l-2HG back to 2-KG. Using loss-of-function mutants, we show that the electrons produced in the l-2HGDH reaction are transferred to the mitochondrial electron transport chain through the electron transfer protein (ETF). Thus, plants possess the biochemical components of an l-2HG metabolic repair system identical to that found in mammals. While deficiencies in the metabolism of l-2HG result in fatal disorders in mammals, accumulation of l-2HG in plants does not adversely affect their development under a range of tested conditions. However, orthologs of l-2HGDH are found in all examined genomes of viridiplantae, indicating that the repair reaction we identified makes an essential contribution to plant fitness in as yet unidentified conditions in the wild. © 2015 The Author 2015.
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17.
  • Ingelsson, Björn, et al. (författare)
  • PeptidylProlyl Isomerase Activity in Chloroplast Thylakoid Lumen is a Dispensable Function of Immunophilins in Arabidopsis thaliana
  • 2009
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 50:10, s. 1801-1814
  • Tidskriftsartikel (refereegranskat)abstract
    • Chloroplast thylakoid lumen of Arabidopsis thaliana contains 16 immunophilins, five cyclophilins and 11 FK506-binding proteins (FKBPs), which are considered protein folding catalysts, although only two of them, AtFKBP13 and AtCYP20-2, possess peptidylprolyl cis/trans isomerase (PPIase) activity. To address the question of the physiological significance of this activity, we obtained and characterized Arabidopsis mutants deficient in the most active PPIase, AtFKBP13, and a double mutant deficient in both AtFKBP13 and AtCYP20-2. Two-dimensional gel electrophoresis of isolated thylakoid lumen, as well as immunoblotting analyses of major photosynthetic membrane protein complexes did not reveal differences in protein composition between the mutants and the wild type. No changes in the relative content of photosynthetic proteins were found by differential stable isotope labeling and liquid chromatographymass spectrometry (LC-MS) analyses. PPIase activity was measured in vitro in isolated thylakoid lumen samples using two different synthetic peptide substrates. Depending on the peptide substrate used for the assay, the PPIase activity in the thylakoid lumen of the mutants lacking either AtFKBP13 or both AtFKBP13 and AtCYP20-2 was as low as 10 or 2 of that in the wild type. Residual PPIase activity detected in the double mutant originated from AtCYP20-3, a cyclophilin from chloroplast stroma contaminating thylakoid lumen preparations. None of the mutants differed from the wild-type plants when grown under normal, cold stress or high light conditions. It is concluded that cellular functions of immunophilins in the thylakoid lumen of chloroplasts are not related to their PPIase capacity and should be investigated beyond this enzymatic activity.
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18.
  • Ivanov, Alexander G, et al. (författare)
  • Digalactosyl-diacylglycerol deficiency impairs the capacity for photosynthetic intersystem electron transport and state transitions in Arabidopsis thaliana due to photosystem I acceptor-side limitations.
  • 2006
  • Ingår i: Plant Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 47:8, s. 1146-57
  • Tidskriftsartikel (refereegranskat)abstract
    • Compared with wild type, the dgd1 mutant of Arabidopsis thaliana exhibited a lower amount of PSI-related Chl–protein complexes and lower abundance of the PSI-associated polypeptides, PsaA, PsaB, PsaC, PsaL and PsaH, with no changes in the levels of Lhca1–4. Functionally, the dgd1 mutant exhibited a significantly lower light-dependent, steady-state oxidation level of P700 (P700+) in vivo, a higher intersystem electron pool size, restricted linear electron transport and a higher rate of reduction of P700+ in the dark, indicating an increased capacity for PSI cyclic electron transfer compared with the wild type. Concomitantly, the dgd1 mutant exhibited a higher sensitivity to and incomplete recovery of photoinhibition of PSI. Furthermore, dgd1 exhibited a lower capacity to undergo state transitions compared with the wild type, which was associated with a higher reduction state of the plastoquinone (PQ) pool. We conclude that digalactosyl-diacylglycerol (DGDG) deficiency results in PSI acceptor-side limitations that alter the flux of electrons through the photosynthetic electron chain and impair the regulation of distribution of excitation energy between the photosystems. These results are discussed in terms of thylakoid membrane domain reorganization in response to DGDG deficiency in A. thaliana.
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19.
  • Klenell, Markus, et al. (författare)
  • Involvement of the chloroplast signal recognition particle cpSRP43 in acclimation to conditions promoting photooxidative stress in Arabidopsis
  • 2005
  • Ingår i: Plant and Cell Physiology. - Oxford : Oxford University Press. - 0032-0781 .- 1471-9053. ; 46:1, s. 118-129
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, we have investigated the role of the CAO gene (coding for the chloroplast recognition particle cpSRP43) in the protection against and acclimation to environmental conditions that promote photooxidative stress. Deficiency of cpSRP43 in the Arabidopsis mutant chaos has been shown previously to lead to partial loss of a number of proteins of the photosystem II (PSII) antennae. In addition, as reported here, mutant plants have lower growth rates and reduced lignin contents under laboratory conditions. However, chaos seedlings showed significantly higher tolerance to photooxidative stress under both tightly controlled laboratory conditions and highly variable conditions in the field. This greater tolerance of chaos plants was manifested in less photooxidative damage together with faster growth recovery in young seedlings. It was also associated with a lower production of H2O2, lower ascorbate levels and less induction of ascorbate peroxidases. Under field conditions, chaos exhibited better overall photosynthetic performance and had higher survival rates. Expression of the CAO gene may be regulated by a light-dependent chloroplastic redox signalling pathway, and was inhibited during acclimation to high light and chilling temperatures, simultaneously with induction of ascorbate peroxidases. It is concluded that the presence/absence of the CAO gene has an impact on photo-produced H2O2, lignification in the hypocotyls and on the plant's susceptibility to photooxidative stress. Therefore, regulation of the CAO gene may be part of the plant's system for acclimation to high light and chilling temperatures.
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20.
  • Leiva, Nélida, et al. (författare)
  • Differential Expression Patterns of Non-symbiotic Hemoglobins in Sugar beet (Beta vulgaris ssp. vulgaris).
  • 2014
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 55:4, s. 834-844
  • Tidskriftsartikel (refereegranskat)abstract
    • Biennial sugar beet (Beta vulgaris spp. vulgaris) is a Caryophyllidae that has adapted its growth cycle to the seasonal temperature and day length variation of temperate regions. This is the first time a holistic study of the expression pattern of non-symbiotic hemoglobins (nsHbs) is being carried out in a member of this group and under two essential environmental conditions for flowering, namely vernalization and length of photoperiod. BvHbs were identified by sequence homology searches against the latest draft of the sugar beet genome. Three nsHbs (BvHb1.1, BvHb1.2, and BvHb2) and one truncated Hb (BvHb3) were found in the genome of sugar beet. Gene expression profiling of the nsHbs was carried out by quantitative PCR in different organs and developmental stages as well as during vernalization and under different photoperiods. BvHb1.1 and BvHb2 showed differential expression during vernalization as well as during long and short days. The high expression of BvHb2 indicates that it has an active role in the cell, maybe even taking over some BvHb1.2 functions, except during germination where BvHb1.2 together with BvHb1.1 -both class 1 nsHbs- are highly expressed. The unprecedented finding of a leading peptide at the N-terminus of BvHb1.1, an nsHb from higher plants together with its observed expression indicate that it may have a very specific role due to its suggested location in chloroplasts. Our findings open up new possibilities for research, breeding and engineering since Hbs could be more involved in plant development than previously was anticipated.
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21.
  • Li, Chao, et al. (författare)
  • The β-Ketoacyl-CoA Synthase Hv KCS1, Encoded by Cer-zh, Plays a Key Role in Synthesis of Barley Leaf Wax and Germination of Barley Powdery Mildew
  • 2018
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 59:4, s. 806-822
  • Tidskriftsartikel (refereegranskat)abstract
    • The cuticle coats the primary aerial surfaces of land plants. It consists of cutin and waxes, which provide protection against desiccation, pathogens and herbivores. Acyl cuticular waxes are synthesized via elongase complexes that extend fatty acyl precursors up to 38 carbons for downstream modification pathways. The leaves of 21 barley eceriferum (cer) mutants appear to have less or no epicuticular wax crystals, making these mutants excellent tools for identifying elongase and modification pathway biosynthetic genes. Positional cloning of the gene mutated in cer-zh identified an elongase component, β-ketoacyl-CoA synthase (CER-ZH/HvKCS1) that is one of 34 homologous KCSs encoded by the barley genome. The biochemical function of CER-ZH was deduced from wax and cutin analyses and by heterologous expression in yeast. Combined, these experiments revealed that CER-ZH/HvKCS1 has a substrate specificity for C 16 -C 20, especially unsaturated, acyl chains, thus playing a major role in total acyl chain elongation for wax biosynthesis. The contribution of CER-ZH to water barrier properties of the cuticle and its influence on the germination of barley powdery mildew fungus were also assessed.
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22.
  • Li, Xue-Yuan, et al. (författare)
  • Development of Industrial Oil Crop Crambe abyssinica for Wax Ester Production through Metabolic Engineering and Cross Breeding
  • 2019
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 60, s. 1274-1283
  • Tidskriftsartikel (refereegranskat)abstract
    • As an important industrial feedstock, wax esters ( WEs) have been used as lubricants in a number of technical processes. There is however currently no large-scale biological source for WE production and alteration in metabolic pathways of plant oils for producing WEs could be attractive to the commercial markets. Here, we present the breeding results of long-term studies on successful development of new crambe lines producing WEs through genetic engineering and cross breeding. The transgenic crambe lines producing WEs at over 25% of the total seed oil were first generated by introduction of the jojoba WE biosynthetic genes ScFAR and ScWS. Further improvement of the lines aiming at improving oxidative stability of WEs was achieved through introducing the CaFAD2-RNAi gene into these lines by crossing. The hybrid lines possessed similar agronomic traits to the wild type and a stable level of WEs over several generations, suggesting a high potential of crambe as an industrial crop for WE production.
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23.
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24.
  • Liu, Yunjun, et al. (författare)
  • The mitochondrial external NADPH dehydrogenase modulates the leaf NADPH/NADP+ ratio in transgenic Nicotiana sylvestris
  • 2008
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 49:1, s. 251-263
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant mitochondria contain alternative external NAD(P)H dehydrogenases, which oxidise cytosolic NADH or NADPH and reduce ubiquinone without inherent linkage to proton pumping and ATP production. In potato, St-NDB1 is an external Ca2+-dependent NADPH dehydrogenase. The physiological function of this enzyme was investigated in homozygous Nicotiana sylvestris lines overexpressing St-ndb1 and co-suppressing St-ndb1 and an N. sylvestris ndb1. In leaf mitochondria isolated from the overexpressor lines, higher activity of alternative oxidase (AOX) was detected. However, the AOX induction was substantially weaker than in the complex I deficient CMSII mutant, previously shown to contain elevated amounts of NAD(P)H dehydrogenases and AOX. An aox1b and an aox2 gene were up-regulated in CMSII, but only aox1b showed a response, albeit smaller, in the transgenic lines, indicating differences in AOX activation between the genotypes. As in CMSII, the increase of AOX in the overexpressing lines was not due to a general oxidative stress. The lines overexpressing St-ndb1 had consistently lowered leaf NADPH/NADP+ ratios in the light and variably decreased levels in darkness, but unchanged NADH/NAD+ ratios. CMSII instead had similar NADPH/NADP+ and lower NADH/NAD+ ratios than wildtype. These results demonstrate that St-NDB1 is able to modulate the cellular balance of NADPH and NADP+ at least in the day and that reduction of NADP(H) and NAD(H) is independently controlled. Similar growth rates, chloroplast malate dehydrogenase activation and xanthophyll ratios indicate that the change in reduction does not communicate to the chloroplast, and that the cell tolerates significant changes in NADP(H) reduction without deleterious effects.
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25.
  • Meng, Meng, et al. (författare)
  • UDP-glucose pyrophosphorylase is not rate limiting, but is essential in arabidopsis
  • 2009
  • Ingår i: Plant and Cell Physiology. - Kyoto : Japanese society of plant physiologists. - 0032-0781 .- 1471-9053. ; 50:5, s. 998-1011
  • Tidskriftsartikel (refereegranskat)abstract
    • UDP-glucose pyrophosphorylase (UGPase) produces UDP-glucose which is essential for sucrose and polysaccharide synthesis. Using Arabidopsis, we demonstrated that two UGPase genes (UGP1 and UGP2) are differentially expressed in a variety of organs, with UGP1 being pre-dominant. Co-expression analyses of UGP genes suggest that UGP1 is closely co-regulated with carbohydrate metabolism genes, late embryogenesis and seed loading, while UGP2 is co-regulated with stress response genes, fertilized flowers and photosynthetic genes. We have used Arabidopsis mutants for the UGP genes to characterize the role of both genes. The UGPase activity/protein was reduced by 70, 10 and 85% in ugp1, ugp2 and ugp1/ugp2 double mutant (DK) plants, respectively. A decrease in UGPase activity/protein was accompanied by an increase in expression of USP, a gene for UDP-sugar pyrophos-phorylase, suggesting a compensatory mechanism. Generally, the mutants had no effects on soluble sugar/starch content (except in certain cases for DK plants), and there were no differences in cell wall composition/content between the wild type and the mutants. On the other hand, DK plants had greater hypocotyl and root lengths. When grown in the field, the mutants had as much as a 50% decrease in the number of seeds produced (consistent with a substantial decrease in field fitness), suggesting that they would be outcompeted in the field in a few generations. Overall, the data suggest that UGPase is not rate limiting for sucrose/starch and cell wall synthesis, but that it is essential in Arabidopsis.
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26.
  • Minina, Alyona, et al. (författare)
  • Suppression of Metacaspase- and Autophagy-Dependent Cell Death Improves Stress-Induced Microspore Embryogenesis in Brassica napus
  • 2020
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 61, s. 2097-2110
  • Tidskriftsartikel (refereegranskat)abstract
    • Microspore embryogenesis is a biotechnological process that allows us to rapidly obtain doubled-haploid plants for breeding programs. The process is initiated by the application of stress treatment, which reprograms microspores to embark on embryonic development. Typically, a part of the microspores undergoes cell death that reduces the efficiency of the process. Metacaspases (MCAs), a phylogenetically broad group of cysteine proteases, and autophagy, the major catabolic process in eukaryotes, are critical regulators of the balance between cell death and survival in various organisms. In this study, we analyzed the role of MCAs and autophagy in cell death during stress-induced microspore embryogenesis in Brassica napus. We demonstrate that this cell death is accompanied by the transcriptional upregulation of three BnMCA genes (BnMCA-Ia, BnMCA-IIa and BnMCA-IIi), an increase in MCA proteolytic activity and the activation of autophagy. Accordingly, inhibition of autophagy and MCA activity, either individually or in combination, suppressed cell death and increased the number of proembryos, indicating that both components play a pro-cell death role and account for decreased efficiency of early embryonic development. Therefore, MCAs and/or autophagy can be used as new biotechnological targets to improve in vitro embryogenesis in Brassica species and doubled-haploid plant production in crop breeding and propagation programs.
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27.
  • Miskiewicz, E, et al. (författare)
  • Photosynthetic acclimation of the Filamentous Cyanobacterium Plectonema boryanum UTEX 485 to Temperature and Light.
  • 2000
  • Ingår i: Plant and Cell Physiology. - 0032-0781 .- 1471-9053. ; 41:6, s. 767-775
  • Tidskriftsartikel (refereegranskat)abstract
    • Photosynthetic acclimation to temperature and irradiance was studied in the filamentous, non-heterocystous cyanobacterium Plectonema boryanum UTEX 485. Growth rates of this cyanobacterium measured at ambient CO2 were primarily influenced by temperature with minimal effects of irradiance. Both growth temperature and irradiance affected linolenic (18:3) and linoleic acid (18:2) levels in the four major lipid classes in an independent but additive manner. In contrast, photosynthetic acclimation was not due to either growth temperature or irradiance per se, but rather, due to the interaction of these environmental factors. P. boryanum grown at low temperature and moderate irradiance mimicked cells grown at high light. Compared to cells grown at either 29°C/150 μmol m-2 s-1 (29/150) or 15/10, P. boryanum grown at either 15/150 or 29/750 exhibited: (1) reduced cellular levels of Chl a and phycobilisomes (PBS), and concomitantly higher content of an orange-red carotenoid, myxoxanthophyll; (2) higher light saturated rates (Pmax) when expressed on a Chl a basis but lower apparent quantum yields of oxygen evolution and (3) enhanced resistance to high light stress. P. boryanum grown at 15/150 regained normal blue-green pigmentation within 16 h after a temperature shift to 29°C at a constant irradiance of 150 μmol m-2 s-1. DBMIB and KCN but not DCMU and atrazine partially inhibited the change in myxoxanthophyll/Chl a ratio following the shift from 15 to 29°C. We conclude that P boryanum responds to either varying growth temperature or varying growth irradiance by adjusting the ability to absorb light through decreasing the cellular contents of Chl a and light-harvesting pigments and screening of excessive light by myxoxanthophyll predominantly localized in the cell wall/cell membrane to protect PSII from over-excitation. The possible role of redox sensing/signalling for photosynthetic acclimation of cyanobacteria to either temperature or irradiance is discussed.
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28.
  • Nishikubo, Nobuyuki, et al. (författare)
  • Xyloglucan endo-transglycosylase (XET) functions in gelatinous layers of tension wood fibers in poplar - A glimpse into the mechanism of the balancing act of trees
  • 2007
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 48:6, s. 843-855
  • Tidskriftsartikel (refereegranskat)abstract
    • Tension wood is a specialized tissue of deciduous trees that functions in bending woody stems to optimize their position in space. Tension wood fibers that develop on one side of the stem have an increased potency to shrink compared with fibers on the opposite side, thus creating a bending moment. It is believed that the gelatinous (G) cell wall layer containing almost pure cellulose of tension wood fibers is pivotal to their shrinking. By analyzing saccharide composition and linkage in isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant. Xyloglucan, xyloglucan endo-transglycosylase (XET) activity and xyloglucan endo-transglycosylase/hydrolase (XTH) gene products were detected in developing G-layers by labeling using CCRC-M1 monoclonal antibody, in situ incorporation of XXXG-SR and the polyclonal antibody to poplar PttXET16-34, respectively, indicating that xyloglucan is incorporated into the G-layer during its development. Moreover, several XTH transcripts were altered and were generally up-regulated in developing tension wood compared with normal wood. In mature G-fibers, XTH gene products were detected in the G-layers while the XET activity was evident in the adjacent S-2 wall layer. We propose that XET activity is essential for G-fiber shrinking by repairing xyloglucan cross-links between G- and S-2-layers and thus maintaining their contact. Surprisingly, XTH gene products and XET activity persisted in mature G-fibers for several years, suggesting that the enzyme functions after cell death repairing the cross-links as they are being broken during the shrinking process.
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29.
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30.
  • Rasmusson, Allan G., et al. (författare)
  • Molecular characterisation of the 76 kDa iron-sulphur protein subunit of potato mitochondrial complex I
  • 1998
  • Ingår i: Plant and Cell Physiology. - 0032-0781. ; 39:4, s. 373-381
  • Tidskriftsartikel (refereegranskat)abstract
    • Genes encoding subunits of complex I (EC 1.6.5.3) of the mitochondrial respiratory chain vary in their locations between the mitochondrial and nuclear genomes in different organisms, whereas genes for a homologous multisubunit complex in chloroplasts have to date only been found on the plastid genome. In potato (Solanum tuberosum L.), the gene coding for the mitochondrial 76 kDa iron-sulphur protein is identified in the nuclear genome. The gene is transcribed into polyadenylated mRNA which is most abundant in flowers, and more frequent in tubers than in leaves. The amino acid sequence is well conserved relative to the nuclear-encoded 75 kDa and 78 kDa subunits of Bos taurus and Neurospora crassa, respectively, and to the Paracoccus denitrificans homologue, most prominently in the region presumed to carry the iron-sulphur clusters. Polyclonal antibodies directed against the 78 kDa complex I subunit of N. crassa recognise the 76 kDa polypeptide in potato mitochondrial complex I, and additionally a polypeptide of 75 kDa in solubilised stroma thylakoids from spinach chloroplasts. The 32 amino acid residues long presequence of the potato mitochondrial 76 kDa complex I subunit targets the precursor polypeptide into isolated potato mitochondria but not into isolated chloroplasts. These results suggest that chloroplast stroma thylakoids contain a protein similar in size and antigenicity to, but genetically distinct from, the mitochondrial subunit.
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31.
  • Saavedra, Laura, et al. (författare)
  • Characterization of phosphatidylinositol phosphate kinases from the moss Physcomitrella patens : PpPIPK1 and PpPIPK2
  • 2009
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 50:3, s. 595-609
  • Tidskriftsartikel (refereegranskat)abstract
    • Phosphoinositides (PIs) play a major role in eukaryotic cells, despite being a minor component of most membranes. This is the first report on PI metabolism in a bryophyte, the moss Physcomitrella patens. Moss PI composition is similar to that of other land plants growing under normal conditions. In contrast to the large number of PIPK genes present in flowering plants, the P. patens genome encodes only two type I/II PIPK genes, PpPIPK1 and PpPIPK2, which are very similar at both the nucleotide and protein product levels. However, the expression of the two genes is differentially regulated, and in vitro biochemical characterization shows that the resulting enzymes have different substrate specificities. PpPIPK1 uses PtdIns4P and PtdIns3P with similar preference and also metabolizes PtdIns(3,4)P(2) to produce PtdIns(3,4,5)P(3), a PI not yet detected in intact plant cells. PpPIPK2 prefers PtdIns as substrate and is much less active towards PtdIns4P and PtdIns3P. Thus, PpPIPK2 shows properties reminiscent of both PtdInsP-kinase and PtdIns-kinases. Moreover, a substitution of glutamic acid by alanine in the activation loop drastically reduced PpPIPK1 activity and altered the substrate specificity to PtdIns5P being the preferred substrate compared with PtdIns4P and PtdIns3P. These findings demonstrate that the substrate specificity of plant PIPKs is determined in a plant-specific manner, which provides new insights into the regulatory modes of PIPK activity in plants.
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32.
  • Salomon, Björn (författare)
  • The Domestication Syndrome Genes Responsible for the Major Changes in Plant Form in the Triticeae Crops
  • 2011
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 52, s. 738-749
  • Forskningsöversikt (refereegranskat)abstract
    • The process of crop domestication began 10,000 years ago in the transition of early humans from hunter/gatherers to pastoralists/farmers. Recent research has revealed the identity of some of the main genes responsible for domestication. Two of the major domestication events in barley were (i) the failure of the spike to disarticulate and (ii) the six-rowed spike. The former mutation increased grain yield by preventing grain loss after maturity, while the latter resulted in an up to 3-fold increase in yield potential. Here we provide an overview of the disarticulation systems and inflorescence characteristics, along with the genes underlying these traits, occurring in the Triticeae tribe.
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33.
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34.
  • Savitch, Leonid V., et al. (författare)
  • Regulation of energy partitioning and alternative electron transport pathways during cold acclimation of lodgepole pine is oxygen dependent
  • 2010
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 51:9, s. 1555-1570
  • Tidskriftsartikel (refereegranskat)abstract
    • Second year needles of Lodgepole pine (Pinus contorta L.) were exposed for 6 weeks to either simulated control summer [summer; 25C/250 photon flux denisty (PFD)], autumn (autumn; 15C/250 PFD) or winter conditions (winter; 5C/250 PFD). We report that the proportion of linear electron transport utilized in carbon assimilation (ETRCO2) was 40 lower in both autumn and winter pine when compared with the summer pine. In contrast, the proportion of excess photosynthetic linear electron transport (ETRexcess) not used for carbon assimilation within the total ETRJf increased by 30 in both autumn and winter pine. In autumn pine acclimated to 15C, the increased amounts of excess electrons were directed equally to 21kPa O-2-dependent and 2kPa O-2-dependent alternative electron transport pathways and the fractions of excitation light energy utilized by PSII photochemistry ((PSII)), thermally dissipated through (NPQ) and dissipated by additional quenching mechanism(s) ((f,D)) were similar to those in summer pine. In contrast, in winter needles acclimated to 5C, 60 of photosynthetically generated excess electrons were utilized through the 2kPa O-2-dependent electron sink and only 15 by the photorespiratory (21kPa O-2) electron pathway. Needles exposed to winter conditions led to a 3-fold lower (PSII), only a marginal increase in (NPQ) and a 2-fold higher (f,D), which was O-2 dependent compared with the summer and autumn pine. Our results demonstrate that the employment of a variety of alternative pathways for utilization of photosynthetically generated electrons by Lodgepole pine depends on the acclimation temperature. Furthermore, dissipation of excess light energy through constitutive non-photochemical quenching mechanisms is O-2 dependent.
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35.
  • Smith, Millicent, et al. (författare)
  • Carbon isotope composition of carbohydrates and polyols in leaf and phloem sap of Phaseolus vulgaris L. influences predictions of plant water use efficiency
  • 2016
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 57:8, s. 1756-1766
  • Tidskriftsartikel (refereegranskat)abstract
    • The use of carbon isotope abundance (δ13C) to assess plant carbon acquisition and water use has significant potential for use in crop management and plant improvement programs. Utilizing Phaseolus vulgaris L. as a model system, this study demonstrates the occurrence and sensitivity of carbon isotope fractionation during the onset of abiotic stresses between leaf and phloem carbon pools. In addition to gas exchange data, compound-specific measures of carbon isotope abundance and concentrations of soluble components of phloem sap were compared with major carbohydrate and sugar alcohol pools in leaf tissue. Differences in both δ13C and concentration of metabolites were found in leaf and phloem tissues, the magnitude of which responded to changing environmental conditions. These changes have inplications for the modeling of leaf-level gas exchange based upon δ13C natural abundance. Estimates of δ13C of low molecular weight carbohydrates and polyols increased the precision of predictions of water use efficiency compared with those based on bulk soluble carbon. The use of this technique requires consideration of the dynamics of the δ13C pool under investigation. Understanding the dynamics of changes in δ13C during movement and incorporation into heterotrophic tissues is vital for the continued development of tools that provide information on plant physiological performance relating to water use.
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36.
  • Son, Ora, et al. (författare)
  • ATHB12, an ABA-Inducible Homeodomain-Leucine Zipper (HD-Zip) Protein of Arabidopsis, Negatively Regulates the Growth of the Inflorescence Stem by Decreasing the Expression of a Gibberellin 20-Oxidase Gene
  • 2010
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 51:9, s. 1537-1547
  • Tidskriftsartikel (refereegranskat)abstract
    • Arabidopsis thaliana homeobox 12 (ATHB12) is rapidly induced by ABA and water stress. A T-DNA insertion mutant of ATHB12 with a reduced level of ATHB12 expression in stems had longer inflorescence stems and reduced sensitivity to ABA during germination. A high level of transcripts of gibberellin 20-oxidase 1 (GA20ox1), a key enzyme in the synthesis of gibberellins, was detected in athb12 stems, while transgenic lines overexpressing ATHB12 (A12OX) had a reduced level of GA20ox1 in stems. Consistent with these data, ABA treatment of wild-type plants resulted in decreased GA20ox1 expression whereas ABA treatment of the athb12 mutant gave rise to slightly decreased GA20ox1 expression. Retarded stem growth in 3-week-old A12OX plants was rescued by exogenous GA(9), but not by GA(12), and less GA(9) was detected in A12OX stems than in wild-type stems. These data imply that ATHB12 decreases GA20ox1 expression in stems. On the other hand, the stems of A12OX plants grew rapidly after the first 3 weeks, so that they were almost as high as wild-type plants at about 5 weeks after germination. We also found changes in the stems of transgenic plants overexpressing ATHB12, such as alterations of expression GA20ox and GA3ox genes, and of GA(4) levels, which appear to result from feedback regulation. Repression of GA20ox1 by ATHB12 was confirmed by transfection of leaf protoplasts. ABA-treated protoplasts also showed increased ATHB12 expression and reduced GA20ox1 expression. These findings all suggest that ATHB12 negatively regulates the expression of a GA 20-oxidase gene in inflorescence stems.
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37.
  • Struglics, André, et al. (författare)
  • Phosphoproteins and protein kinase activities intrinsic to inner membranes of potato tuber mitochondria
  • 1999
  • Ingår i: Plant and Cell Physiology. - 0032-0781. ; 40:12, s. 1271-1279
  • Tidskriftsartikel (refereegranskat)abstract
    • Inside-out submitochondrial particles (IO-SMP) were isolated and purified from potato (Solanum tuberosum L. cv.) tubers. When these IO-SMP were incubated with [γ32P]ATP more then 20 proteins became labelled as a result of phosphorylation. The 32P incorporation was stimulated by the oxidizing reagent ferricyanide. Except for a 17 kDa protein which was phosphorylated only in the absence of divalent cations, the protein phosphorylation required Mg2+. The time for half-maximum 32P incorporation was 4 min for the 22 kDa phospho-F1 δ-subunit and 2 min for the 28 kDa phospho-F0 b-subunit of the proton-ATPase. The K(m) for ATP for the detected phosphoproteins was between 65 μM and 110 μM. The pH optimum for protein phosphorylation in inner membranes was between pH 6 and 8, and for the F1 δ-subunit and the F0 b-subunit the pH optima were 6.5-8 and pH 8, respectively. A 37 kDa phosphoprotein was phosphorylated on a histidine residue while the remainder of the inner membrane proteins were phosphorylated on serine or threonine residues. Two autophosphorylated putative kinases were identified: one at 16.5 kDa required divalent cations for autophosphorylation, while another at 30 kDa did not. A 110 kDa protein was labelled only with [α-32P]ATP, suggesting adenylylation.
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38.
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39.
  • Sävenstrand, Helena, et al. (författare)
  • Regulation of gene expression by low levels of ultraviolet-B radiation in Pisum sativum : isolation of novel genes by suppression subtractive hybridisation
  • 2002
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 43:4, s. 402-410
  • Tidskriftsartikel (refereegranskat)abstract
    • Suppression subtractive hybridisation was used to isolate genes differentially regulated by low levels (UV-B(BE,300) 0.13 W m(-2)) of ultraviolet-B radiation (UV-B; 290-320 nm) in Pisum sativum. Six genes were regulated, two of which were novel. The mRNA levels for these two (PsTSDC and PsUOS1) were increased and depressed by UV-B treatment, respectively. Domains in the PsTSDC translation product was similar to TIR (Toll-Interleukin-1 receptor-similar) domains and a NB-ARC domain (nucleotide-binding domain in APAF-1, R gene products and CED-4). The PsUOS1 translation product was similar to an open reading frame in Arabidopsis. Genes encoding embryo-abundant protein (PsEMB) and S-adenosyl-L-methionine synthase (PsSAMS) were induced by UV-B, whereas the transcript levels for genes encoding sucrose transport protein (PsSUT) or ribulose-5-phosphate 3-epimerase (PsR5P3E) were decreased. These regulation patterns are novel, and the PsEMB and PsR5P3E sequences are reported for the first time. The stress-specificity of regulation of these genes were tested by ozone fumigation (100 ppb O(3)). Qualitatively, the similarity of expression after both UV-B and ozone exposure suggests that, for these genes, similar stress-response pathways are in action.
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40.
  • Takahashi Schmidt, Junko, et al. (författare)
  • KORRIGAN1 and its Aspen Homolog PttCel9A1 Decrease Cellulose Crystallinity in Arabidopsis Stems
  • 2009
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 50:6, s. 1099-1115
  • Tidskriftsartikel (refereegranskat)abstract
    • KORRIGAN1 (KOR1) is a membrane-bound cellulase implicated in cellulose biosynthesis. PttCel9A1 from hybrid aspen (Populus tremula L. tremuloides Michx.) has high sequence similarity to KOR1 and we demonstrate here that it complements kor1-1 mutants, indicating that it is a KOR1 ortholog. We investigated the function of PttCel9A1/KOR1 in Arabidopsis secondary growth using transgenic lines expressing 35S::PttCel9A1 and the KOR1 mutant line irx2-2. The presence of elevated levels of PttCel9A1/KOR1 in secondary walls of 35S::PttCel9A1 lines was confirmed by in muro visualization of cellulase activity. Compared with the wild type, 35S::PttCel9A1 lines had higher trifluoroacetic acid (TFA)-hydrolyzable glucan contents, similar Updegraff cellulose contents and lower cellulose crystallinity indices, as determined by C-13 solid-state nuclear magnetic resonance (NMR) spectroscopy. irx2-2 mutants had wild-type TFA-hydrolyzable glucan contents, but reduced Updegraff cellulose contents and higher than wild-type cellulose crystallinity indices. The data support the hypothesis that PttCel9A1/KOR1 activity is present in cell walls, where it facilitates cellulose biosynthesis in a way that increases the amount of non-crystalline cellulose.
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41.
  • Wallström, Sabá, et al. (författare)
  • Suppression of NDA-type alternative mitochondrial NAD(P)H dehydrogenases in Arabidopsis thaliana modifies growth and metabolism, but not high light stimulation of mitochondrial electron transport.
  • 2014
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 55:5, s. 881-896
  • Tidskriftsartikel (refereegranskat)abstract
    • The plant respiratory chain contains several pathways which bypass the energy-conserving electron transport complexes I, III, and IV. These energy-bypasses, including type II NAD(P)H dehydrogenases and the alternative oxidase (AOX), may have a role in redox-stabilisation and regulation, but current evidence is inconclusive. Using RNA interference, we generated Arabidopsis thaliana plants simultaneously suppressing the type II NAD(P)H dehydrogenase genes NDA1 and NDA2. Leaf mitochondria contained substantially reduced levels of both proteins. In sterile culture in the light, the transgenic lines displayed a slow growth phenotype, which was more severe when the complex I inhibitor rotenone was present. Slower growth was also observed in soil. In rosette leaves, a higher NAD(P)H/NAD(P)(+)-ratio and elevated levels of lactate relative to sugars and citric acid cycle metabolites were observed. However, photosynthetic performance was unaffected and microarray analyses indicated few transcriptional changes. A high light treatment increased AOX1a mRNA levels, in vivo AOX and cytochrome oxidase activities, and levels of citric acid cycle intermediates and hexoses in all genotypes. However, NDA-suppressing plants deviated from the wild type merely by having higher levels of several amino acids. These results suggest that NDA-suppression restricts citric acid cycle reactions, inducing a shift towards increased levels of fermentation products, but do not support a direct association between photosynthesis and NDA proteins.
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42.
  • Wei, Wenxue, et al. (författare)
  • HvPIP1;6, a barley (Hordeum vulgare L.) plasma membrane water channel particularly expressed in growing compared with non-growing leaf tissues
  • 2007
  • Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 48:8, s. 1132-1147
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the present study was to identify water channel(s) which are expressed specifically in the growth zone of grass leaves and may facilitate growth-associated water uptake into cells. Previously, a gene had been described (HvEmip) which encodes a membrane intrinsic protein (MIP) and which is particularly expressed in the base I cm of barley primary leaves. The functionality of the encoding protein was not known. In the present study on leaf 3 of barley (Hordeum vulgare L.), a clone was isolated, termed HvPIP1;6, which has 99% amino acid sequence identity to HvEmip and belongs to the family of plasma membrane intrinsic proteins (PIPs). Expression of HvPIP1;6 was highest in the elongation zone, where it accounted for > 85% of expression of known barley PIP1s. Within the elongation zone, faster grower regions showed higher expression than slower growing regions. Expression of HvPIP1;6 was confined to the epidermis, with some expression in neighboring mesophyll cells. Expression of HvPIP1;6 in Xenopus laevis oocytes increased osmotic water permeability 4- to 6-fold. Water channel activity was inhibited by pre-incubation of oocytes with 50 mu M HgCl2 and increased following incubation with the phosphatase inhibitor okadaic acid or the plant hormone ABA. Plasma membrane preparations were analyzed by Western blots using an antibody that recognized PIP1s. Levels of PIP1s were highest in the elongation and adjacent non-elongation zone. The developmental expression profile of HvPIP2;1, the only known barley water channel belonging to the PIP2 subgroup, was opposite to that of HvPIP1;6.
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