Submitted to: Plant Biology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2010
Publication Date: 6/1/2010
Citation: Ort, D.R., Schwarz, E.M. 2010. Regulation of Chlorophyll Integration into Thylakoid Protein Complexes. Plant Biology Annual Meeting. Available: http://abstracts.aspb.org/pb2010/public/P02/P02064.html. Interpretive Summary:
Technical Abstract: In order to control the useful absorption of light plants must be able to optimize the amount of irradiance each of the photosystems receives. To do so they must modulate both the size of the LHC antenna as well as the ratio of the PSII and PSI photocenters to one another. These changes to the protein complement of the thylakoids require concerted regulation of a variety of cellular processes. Chlorophyll is an indispensable cofactor for the proteins of the light reactions of photosynthesis. Moreover, chlorophyll is photoreacitve and phototoxic, and so can not be allowed to exist freely in the cytosol. The synthesis and degradation of chlorophyll must therefore be tightly coupled to the synthesis and degradation of its binding proteins. Specific 14C metabolic radiolabeling of chlorophyll was used to investigate aspects of photosystem assembly and regulation in Arabidopsis. It was found that newly synthesized chlorophyll is preferentially packaged into LHC, and that increasing light intensities increase chlorophyll synthesis and integration into thylakoid complexes. Chlorophyll protein degradation, by contrast, requires light but is not greatly regulated by light intensity. The effects of light on chlorophyll synthesis, integration, and degradation were found to be mediated by plastoquinone redox. The effect of lastoquinone redox was in turn found to be mediated by the process of state transitions, i.e. LHC association with PSII. Substrate level control of chlorophyll protein integration by thylakoid organization is proposed to control assembly and turnover of thykoid complexes.