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Redox regulation of photosynthetic gene expression.

ABSTRACT: Redox chemistry and redox regulation are central to the operation of photosynthesis and respiration. However, the roles of different oxidants and antioxidants in the regulation of photosynthetic or respiratory gene expression remain poorly understood. Leaf transcriptome profiles of a range of Arabidopsis thaliana genotypes that are deficient in either hydrogen peroxide processing enzymes or in low molecular weight antioxidant were therefore compared to determine how different antioxidant systems that process hydrogen peroxide influence transcripts encoding proteins targeted to the chloroplasts or mitochondria. Less than 10 per cent overlap was observed in the transcriptome patterns of leaves that are deficient in either photorespiratory (catalase (cat)2) or chloroplastic (thylakoid ascorbate peroxidase (tapx)) hydrogen peroxide processing. Transcripts encoding photosystem II (PSII) repair cycle components were lower in glutathione-deficient leaves, as were the thylakoid NAD(P)H (nicotinamide adenine dinucleotide (phosphate)) dehydrogenases (NDH) mRNAs. Some thylakoid NDH mRNAs were also less abundant in tAPX-deficient and ascorbate-deficient leaves. Transcripts encoding the external and internal respiratory NDHs were increased by low glutathione and low ascorbate. Regulation of transcripts encoding specific components of the photosynthetic and respiratory electron transport chains by hydrogen peroxide, ascorbate and glutathione may serve to balance non-cyclic and cyclic electron flow pathways in relation to oxidant production and reductant availability.

SUBMITTER: Queval G

PROVIDER: S-EPMC3497073 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Redox regulation of photosynthetic gene expression.

Queval Guillaume G Foyer Christine H CH

Philosophical transactions of the Royal Society of London. Series B, Biological sciences 20121201 1608

Redox chemistry and redox regulation are central to the operation of photosynthesis and respiration. However, the roles of different oxidants and antioxidants in the regulation of photosynthetic or respiratory gene expression remain poorly understood. Leaf transcriptome profiles of a range of Arabidopsis thaliana genotypes that are deficient in either hydrogen peroxide processing enzymes or in low molecular weight antioxidant were therefore compared to determine how different antioxidant systems ...[more]

PMID: 23148274

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Project description:The triose-phosphate/phosphate translocator (TPT) of the chloroplast inner envelope membrane mediates the counter-exchange of stromal triose phosphates derived from CO2 fixation with cytosolic phosphate, thus providing the cytosol with precursors for sucrose synthesis. We have isolated an Arabidopsis mutant (tpt-1) in which the gene encoding TPT is disrupted by a T-DNA insertion. During growth in low light tpt-1 plants are phenotypically normal, but in high light photosynthesis is inhibited and growth is retarded relative to wildtype. This mutant compensates for the absence of TPT by diverting photosynthate into starch which is hydrolysed and exported from the chloroplast as glucose that is subsequently phosphorylated by hexokinase. In low light the capacity of the pathway of starch synthesis is sufficient to accommodate the normal rate of CO2 fixation, but in high light it is unable to match the potential rate of CO2 fixation. Consequently, in high light-grown plants there are measurable effects on the redoxstate of several components. Thus, the tpt-1 mutation influences the carbohydrate status within the cell, alters the form in which carbon is received by the cytosol, and changes the redox signals that are important in photosynthetic acclimation.Plants will be grown in a 8h light:16h dark regime at both 400 and 100 Âµmol PAR m-2 s-1. Total RNA will be extracted from pools of individual illuminated leaves from at least eight plants at growth stage 3.70. Leaves will be harvested 2 h into the photoperiod to maximises differences between plant lines in the expression of genes of photosynthesis and carbohydrate metabolism. We anticipate that expression of many genes will be affected by the absence of TPT and by changes in light intensity. However, by comparing differences in transcript levels between wildtype and TPT mutant grown in high light with the differences that occur in plants grown in low light we will discriminate between genes whose expression is affected by changes in the pattern of carbohydrate metabolism and those influenced by redox poise of the thylakoid photochemical components. These comparisons will also highlight genes affected by recently identified regulatory interactions between sugar-sensing and redox-sensing. A genome-wide expression study will establish the extent to which gene expression is altered by the absence of TPT in leaves, and will provide the basis for more detailed analysis of a selected range of transcripts whose levels of expression differ between plant lines. Experimenter name = Robin Walters Experimenter phone = 01865 275000 Experimenter fax = 01865 275074 Experimenter address = Dept of Plant Sciences Experimenter address = University of Oxford Experimenter address = South Parks Road Experimenter address = Oxford Experimenter zip/postal_code = OX1 3RB Experimenter country = UK Keywords: growth_condition_design; genetic_modification_design;

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Redox regulation of photosynthetic gene expression.

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Redox regulation of photosynthetic gene expression.

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