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PTOX-dependent safety valve does not oxidize P700 during photosynthetic induction in the Arabidopsis pgr5 mutant
- Source :
- Plant Physiol
- Publication Year :
- 2021
- Publisher :
- Oxford University Press (OUP), 2021.
-
Abstract
- Plastid terminal oxidase (PTOX) accepts electrons from plastoquinol to reduce molecular oxygen to water. We introduced the gene encoding Chlamydomonas reinhardtii (Cr)PTOX2 into the Arabidopsis (Arabidopsis thaliana) wild-type (WT) and proton gradient regulation5 (pgr5) mutant defective in cyclic electron transport around photosystem I (PSI). The accumulation of CrPTOX2 only mildly affected photosynthetic electron transport in the WT background during steady-state photosynthesis but partly complemented the induction of nonphotochemical quenching (NPQ) in the pgr5 background. During the induction of photosynthesis by actinic light (AL) of 130 µmol photons m−2 s−1, the high level of PSII yield (Y(II)) was induced immediately after the onset of AL in WT plants accumulating CrPTOX2. NPQ was more rapidly induced in the transgenic plants than in WT plants. P700 was also oxidized immediately after the onset of AL. Although CrPTOX2 does not directly induce a proton concentration gradient (ΔpH) across the thylakoid membrane, the coupled reaction of PSII generated ΔpH to induce NPQ and the downregulation of the cytochrome b6f complex. Rapid induction of Y(II) and NPQ was also observed in the pgr5 plants accumulating CrPTOX2. In contrast to the WT background, P700 was not oxidized in the pgr5 background. Although the thylakoid lumen was acidified by CrPTOX2, PGR5 was essential for oxidizing P700. In addition to acidification of the thylakoid lumen to downregulate the cytochrome b6f complex (donor-side regulation), PGR5 may be required for draining electrons from PSI by transferring them to the plastoquinone pool. We propose a reevaluation of the contribution of this acceptor-side regulation by PGR5 in the photoprotection of PSI.
- Subjects :
- Chlorophyll
Genotype
Regular Issue Content
Physiology
Arabidopsis
Plastoquinone
macromolecular substances
Plant Science
Photosystem I
Plastid terminal oxidase
Electron Transport
chemistry.chemical_compound
Genetics
Photosynthesis
Electrochemical gradient
P700
Cytochrome b6f complex
Genetic Variation
food and beverages
Plants, Genetically Modified
Electron transport chain
chemistry
Thylakoid
Mutation
Biophysics
Oxidoreductases
Oxidation-Reduction
Chlamydomonas reinhardtii
Subjects
Details
- ISSN :
- 15322548 and 00320889
- Volume :
- 188
- Database :
- OpenAIRE
- Journal :
- Plant Physiology
- Accession number :
- edsair.doi.dedup.....126f5a8816cbd86021771db038f3e3cf