Photosynthetic Electron Flow Regulates Transcription of the psaB Gene in Pea ( Pisum sativum L.) Chloroplasts Through the Redox State of the Plastoquinone Pool

Abstract

Plants respond to changing light conditions by altering the stoichiometry between components of the photosynthetic electron transport chain of chloroplast thylakoids. We measured specific run-on transcription of the chloroplast genes psaB, psbA and rbcL in pea (Pisum sativum L.) seedlings grown under three different conditions of illumination: light selective for photosystem I (PSI-light); light selective for photosystem II (PSII-light); and a combination of PSI- and PSII-light (mixed light, ML). The transcriptional rate of the psaB gene increased under PSII-light and decreased under PSI-light, while the transcriptional rates of the psbA and rbcL genes were affected only in a non-specific way. Similar effects also occurred in plants grown under ML and switched to either PSI- or PSII-light for 4 h. Addition of the inhibitors of photosynthetic electron transport 3-(3,4 dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) influenced psaB transcription in isolated, illuminated chloroplasts: DCMU addition resulted in oxidation of the plastoquinone pool and decreased transcription of psaB; DBMIB addition resulted in reduction of the plastoquinone pool and increased transcription of psaB. The experimental results obtained in vivo and in vitro provide evidence for coupling between the redox state of plastoquinone and the rate of transcription of the psaB gene in pea.

Chloroplast redox signals: how photosynthesis controls its own genes

“…When the PQ pool is oxidized by PSI -light or 3-(3 0 ,4 0 -dichlorophenyl)-1,1 0 -dimethyl urea (DCMU), the opposite is the case. This has been shown for the cyanobacterial genes psbA, psbD, psaA and psaB, which encode the reaction-centre proteins D1, D2, PsaA and PsaB (light-blue boxes) [41] and the chloroplast genes psbA and psaAB (green oval insets) [36,74]. Data from another study in Synechocystis also show that the redox state of a photosynthetic electron carrier activates psbA in its oxidized state and psaE in its reduced state, supporting this model of opposite redox regulation of PSI and PSII genes [89].…”

Dynamic Plastid Redox Signals Integrate Gene Expression and Metabolism to Induce Distinct Metabolic States in Photosynthetic Acclimation inArabidopsis

“…Physiological systems that induce redox signals by generating excitation imbalances between the photosystems were found to be especially useful. Low-intensity excitation with artificial light sources that preferentially excite PSI or PSII (PSI or PSII light, respectively) induce either oxidation or reduction of the photosynthetic electron transport chain without induction of stress-related responses and provide an experimental system that can be used for a wide range of organisms, including cyanobacteria, algae, and plants (Melis and Harvey, 1981;Deng et al, 1989;Chow et al, 1990;Melis et al, 1996;Pfannschmidt et al, 1999;Alfonso et al, 2000;Kovacs et al, 2000;Tullberg et al, 2000;Fan et al, 2007). This light system mimics the natural light quality gradients of dense plant populations and induces typical acclimation responses, such as state transitions and photosystem stoichiometry adjustment.…”

cor Gene Expression in Barley Mutants Affected in Chloroplast Development and Photosynthetic Electron Transport

“…The transcription rate of the nuclear genes coding for the lightharvesting complex II (Lhc; Escoubas et al, 1995) and for PSI subunits (PsaD and PsaF; Pfannschmidt et al, 2001) as well as of the chloroplast genes encoding the reaction center apoproteins of PSI and PSII (Pfannschmidt et al, 1999) is controlled by the redox state of the plastoquinone. A posttranscriptional redox state-dependent regulation has been shown for the chloroplast gene petB encoding the cyt b 6 protein (Tullberg et al, 2000). Changes in the environmental conditions affect the redox state of the chloroplast, whereas exposure to low temperature under light conditions leads to an over-reduction state of the PSII (Gray et al, , 1998.…”

“…Overreduction of plastoquinone pool causes photoinhibition of photosynthesis . The redox state of the plastoquinone controls several functions involved in chloroplast biogenesis: the transcription rate of the chloroplast psaB gene (Tullberg et al, 2000), the transcription (Escoubas et al, 1995) of nuclear genes encoding chloroplast proteins, and also posttranscriptional modification processes (Dickey et al, 1998).Changes in plastoquinone redox state elicit stress response mechanisms . In maize (Zea mays), the cold/light-induced phosphorylation of CP29 is promoted by the over-reduction of the plastoquinone pool (Bergantino et al, 1995;Mauro et al, 1998).…”

“…Overreduction of plastoquinone pool causes photoinhibition of photosynthesis . The redox state of the plastoquinone controls several functions involved in chloroplast biogenesis: the transcription rate of the chloroplast psaB gene (Tullberg et al, 2000), the transcription (Escoubas et al, 1995) of nuclear genes encoding chloroplast proteins, and also posttranscriptional modification processes (Dickey et al, 1998).…”