Characterization of the genetic requirements for photoautotrophic growth under fluctuating light intensities, using novel high-throughput genomics approaches in the green alga Chlamydomonas reinhardtii

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Sun light drives photosynthesis. Photosynthetic organisms experience substantial fluctuations in the availability of this energy source. Their rapid acclimation to changes in light intensity is important for optimal photosynthesis yield. Processes that lead to the acclimation of photosynthetic eukaryotes include mechanisms that sense and regulate the light dependent activity of the photosynthetic electron transport chain. Molecular factors involved in these acclimating processes have been identified with genetic screens for mutants with altered photosynthesis parameters. Some of these mutants show specific growth defects when grown under highly fluctuating light intensities.As a DFG fellow, I propose to systematically identify components important for optimum photoautotrophic growth under highly fluctuating light by performing a cutting-edge genome-wide screen in the green alga Chlamydomonas reinhardtii. Growth rates of hundreds of thousands of mutants will be measured using a pooled strategy where each mutant is identified by a unique DNA barcode. Mutants deficient in rapid acclimation responses will be revealed by their growth defects under fluctuating light conditions, in comparison to a control condition. I hope that this screen will uncover a variety of previously unappreciated pathways and components with roles in short-term acclimation to changes in light intensity.I hypothesize that ion channels in the thylakoid membrane may be specifically important for growth under fluctuating light conditions, because of their role in dissipating the light dependent electric component of the proton motive force. If ion channels are identified in the screen, I will characterize their functional role with spectroscopic analyses of Chlamydomonas mutants and biochemical analyses of the proteins.