Plant and Cell Physiology Advance Access originally published online on September 17, 2008
Plant and Cell Physiology 2008 49(11):1688-1698; doi:10.1093/pcp/pcn140
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Effect of PGR5 Impairment on Photosynthesis and Growth in Arabidopsis thaliana
1 CEA Cadarache, DSV, IBEB, SBVME, Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, Laboratoire dEcophysiologie Moléculaire des Plantes, UMR 6191 CNRS/CEA/Université Aix-Marseille, F-13108 Saint-Paul-lez-Durance, France
*Corresponding author: E-mail, munekage{at}bs.naist.jp; Fax, +81-743-72-5569.
| Abstract |
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PGR5 has been reported as an important factor for the activity of the ferredoxin-dependent cyclic electron transport around PSI. To elucidate the role of PGR5 in C3 photosynthesis, we characterized the photosynthetic electron transport rate (ETR), CO2 assimilation and growth in the Arabidopsis thaliana pgr5 mutant at various irradiances and with CO2 regimes. In low-light-grown pgr5, the CO2 assimilation rate and ETR were similar to the those of the wild type at low irradiance, but decreased at saturating irradiance under photorespiratory conditions as well as non-photorespiratory conditions. Although non-photochemical quenching of chlorophyll fluorescence (NPQ) was not induced in the pgr5 mutant under steady-state photosynthesis, we show that it was induced under dark to light transition at low CO2 concentration. Under low light conditions in air, pgr5 showed the same growth as the wild type, but a significant growth reduction compared with the wild type at >150 µmol photons m–2 s–1. This growth impairment was largely suppressed under high CO2 concentrations. Based on the intercellular CO2 concentration dependency of CO2 assimilation, ETR and P700 oxidation measurements, we conclude that reduction of photosynthesis and growth result from (i) ATP deficiency and (ii) inactivation of PSI. We discuss these data in relation to the role of PGR5-dependent regulatory mechanisms in tuning the ATP/NADPH ratio and preventing inactivation of PSI, especially under conditions of high irradiance or enhanced photorespiration.
Keywords: CO2 assimilation - Cyclic electron transport - Non-photochemical quenching - Photosynthesis - Photoinhibition
Abbreviations: LED, light-emitting diode; NDH, NAD(P)H dehydrogenase; PGR5, PROTON GRADIENT REGULATION 5; ROS, reactive oxygen species; RuBP, ribulose-1,5-bisphosphate.
2Present address: Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, 630-0192 Japan.
(Received July 14, 2008; Accepted September 7, 2008)
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