The onset of NPQ and Deltamu(H)+ upon illumination of tobacco plants studied through the influence of mitochondrial electron transport.
The relationship between the development of photoprotective mechanisms (non-photochemical quenching, NPQ), the generation of the electrochemical proton gradient in the chloroplast and the capacity to assimilate CO(2) was studied in tobacco dark-adapted leaves at the onset of illumination with low light. These conditions induce the generation of a transient NPQ, which relaxes in the light in parallel with the activation of the Calvin cycle. Wild-type plants were compared with a CMSII mitochondrial mutant, which lacks the respiratory complex I and shows a delayed activation of photosynthesis. In the mutant, a slower onset of photosynthesis was mirrored by a decreased capacity to develop NPQ. This correlates with a reduced efficiency to reroute electrons at the PSI reducing side towards cyclic electron flow around PSI and/or other alternative acceptor pools, and with a smaller ability to generate a proton motive force in the light. Altogether, these data illustrate the tight relationship existing between the capacity to evacuate excess electrons accumulated in the intersystem carriers and the capacity to dissipate excess photons during a dark to light transition. These data also underline the essential role of respiration in modulating the photoprotective response in dark-adapted leaves, by poising the cellular redox state.
Cardol
Pierre
P
Laboratoire de Génétique des Microorganismes, Département des Sciences la Vie, 27, Bld du rectorat, Université de Liège, B-4000 Liège, Belgium.
De Paepe
Rosine
R
Franck
Fabrice
F
Forti
Giorgio
G
Finazzi
Giovanni
G
D000255:Adenosine Triphosphate / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D004579:Electron Transport / Q000502:physiology*; D042967:Electron Transport Complex I / Q000235:genetics / Q000378:metabolism*; D008027:Light; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism*; D010777:Photochemistry; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D014026:Nicotiana / Q000528:radiation effects*
D002245:Carbon Dioxide; D000255:Adenosine Triphosphate; D042967:Electron Transport Complex I