Submitted to: Photosynthesis Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2008
Publication Date: 8/1/2008
Publication URL: http://www.springerlink.com/content/?k=10.1007%2fs11120-008-9315-0
Citation: Wu, G., Ort, D.R. 2008. Mutation in cysteine bridge domain of the gamma-subunit affects light regulation of the ATP synthase in Arabidopsis. Photosynthesis Research. 97:185-193. Interpretive Summary: The regulation of key enzymes in photosynthesis by light is a central factor in ensuring efficient energy storage in the rapidly changing light environment of natural habitats. The chloroplast ATP synthase is one of the important enzymes regulated by light ensuring that ATP synthesis can occur efficiently when amble light is available but preventing the wasteful hydrolysis of ATP at night or when light is very low. There are still central features about the light-regulation of ATP synthesis activity that remained to be established and mutants of the light regulation process is one useful approach to further understand this process in leaves. In this paper we report on the analysis of an Arabidopsis site-directed transformants that we produced that interfered with the operation of the ATP synthase. This study is relevant to agricultural and plant scientists interested in the mechanism and purpose of the regulation of photosynthesis by light.
Technical Abstract: The chloroplast ATP synthase functions to synthesize ATP from ADP and free phosphate coupled by the electrochemical potential across the thylakoid membrane in the light. The light-dependent regulation of ATP synthase activity is carried out in part through redox modulation of a cysteine bridge in CF1 gamma-subunit. In order to investigate the function of the redox regulatory domain and the physiological significance of redox modulation for higher plant, we designed four mutations in the gamma-subunit, designated as C199S, C205S, C199/205S and delta 197-205, to create a permanent reduced form of the gamma-subunit. The transgenes were overexpressed in the wild type background. The chloroplast ATPase activities were analyzed. Except delta 197-205 which is similar to the wild type, DTT treatment conferred high activity to the wild type ATPase, while the high ATPase activities in the transgenic plants were independent on DTT treatment indicating that the successful integration of mutated version of the gamma-subunit. The underlying effects of the “permanently reduced” ATP synthase on photosynthesis and biomass accumulation were further investigated. Our result showed that there is no significant difference in photosynthesis rate and growth rate suggesting that higher plant may not benefit from the formation of disulfide bond in the gamma-subunit.