Zhang, Ru , Sharkey, Thomas D. .
Cyclic Electron Transport Protects against Moderate Heat Stress in Arabidopsis thaliana.
Photosynthesis is among the most heat-sensitive functions in plants. However, the mechanism by which moderate heat stress reduces photosynthetic capacity remains unclear. Photosynthesis uses both linear and cyclic electron flows to convert light energy into the transthylakoid proton motive force, composed of the proton gradient and the electric field. Heat stress frequently causes increased cyclic electron transport. Here we used two Arabidopsis thaliana mutants, each deficient in one of the two pathways of cyclic electron flow - crr2 (chlororespiratory reduction, deficient in the chloroplast NAD(P)H dehydrogenase dependent cyclic flow from NADPH to plastoquinone) and pgr5 (proton gradient regulation, deficient in the antimycin A sensitive cyclic flow from ferredoxin to plastoquinone). Heat stress experiments were done in light with intact leaves by switching leaf temperature from 23oC to 40oC in 2 minutes and measuring the electrochromic shift to analyze transthylakoid proton fluxes during photosynthesis. The electrochromic shift results from an electric field effect on carotenoid absorbance bands and is measured at 518 nm. Our result indicated that these two cyclic-electron-transport mutants were more sensitive to heat stress and had less ability to recover than wildtype, especially pgr5. What’s more, the electrochromic shift data showed that the transthylakoid electrical gradient was significantly reduced in pgr5 mutants. We propose that cyclic electron transport protects against moderate heat stress in Arabidopsis thaliana.
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1 - University of Wisconsin-Madison, Department of Botany, 430 Lincoln Dr., Madison, WI, 53706, U.S.A.
2 - University of Wisconsin-Madison, Department of Botany
cyclic electron transport
Presentation Type: ASPB Minisymposium
Location: Continental A/Hilton
Date: Sunday, July 8th, 2007
Time: 5:25 PM