Light harvesting proteins in diatoms - functional heterogeneity and regulation

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The major aim of the project is to examine more deeply the effects of the newly identified, unusual cryptochrome CryP in the pennate diatom Phaeodactylum tricornutum. CryP, having DASH like features according to spectroscopic analyses but also grouping close to plant Crys in sequence analyses, was shown to be involved in the regulation of the overall protein levels of different light-harvesting proteins (fucoxanthin chlorophyll proteins, FCPs). Here, we will focus on the influence of CryP on the organisation of light harvesting proteins. Many FCPs are expressed in diatoms and assemble mostly in trimers, which differ in polypeptide composition and also slightly in pigmentation. We want to use our CryP knockdown lines to test biochemically, which FCP trimers are influenced by the action of CryP. Whether this influence is in relation to the circadian clock will be determined on mRNA level, since CryP is related to plant Crys. In addition, the cellular localization of CryP should be clarified. Since the spectroscopic features of CryP resemble CRY-DASH proteins, its possible bi-functionality, i.e. an involvement in DNA repair, will be tested as well. Spectroscopic and structural investigations on the protein together with mRNA quantifications under different light conditions should provide further insight into the mode of action, as well as the identification of possible interaction partners.