Starter Grant: Biliprotein Function in the Photomorphogenetic Responses of Fremyella diplosiphon (Microbial Biology Starter Grant)

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Cyanobacteria and other photosynthetic organisms possess the ability to finely tune responses to fluctuating illumination. Cyanobacteria contain light-absorbing phycobiliproteins in their photosynthetic light-harvesting antenna complexes, called phycobilisomes. Some cyanobacteria possess the ability to alter the composition and concentrations of the phycobiliproteins contained in their phycobilisomes in response to changes in the photoenvironment. This capacity, called complementary chromatic adaptation, is itself controlled by a photosensory biliprotein, RcaE. RcaE from the cyanobacterium Fremyella diplosiphon is responsive to both green and red light. Recent studies suggest that, in vivo, RcaE requires an enzymatic protein partner for the covalent attachment of its chromophore to a conserved cysteine residue. A long-term goal of this research is to define the light-regulated signal transduction cascade controlled by RcaE. Despite the progress that has been made in understanding the molecular basis of complementary chromatic adaptation, understanding of the light-regulated mechanism of RcaE activity is incomplete. The detailed aims of this project are as follows: (i) the lyase enzyme(s) responsible for covalent attachment of a chromophore to RcaE will be identified by constructing and screening an appropriate expression library, (ii) a bacterial expression system will be used to isolate chromophorylated RcaE, and (iii) the light-regulated, complex phosphorelay cascade initiated by RcaE will be further characterized. A broader impact of this research is to develop the ability of undergraduate science majors and students from underrepresented groups who are participating in the Undergraduate Researchers in Plant Science Program at Michigan State University to think analytically and critically.