From Comparative Genomics to Photosynthetic Function

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Intellectual Merit: Photosynthesis is an astoundingly dynamic process that can be rapidly tuned to environmental change and the development of cells. The tuning of photosynthetic activity is critical for coordinating cellular growth, developmental processes, and environmental conditions with the photosynthetic production of energy, reductants, and fixed carbon (e.g. sugars). Dynamic features of photosynthesis include protein and pigment modifications and conformational adjustments that can take milliseconds, to more extensive remodeling of the photosynthetic machinery that can take from minutes to hours. There are still large gaps in our knowledge concerning mechanisms that coordinate photosynthetic activity with environmental change and developmental processes. This project is focused on identifying and characterizing mutants in a relatively small set of proteins that have been associated with the green plant/algal lineages, but are not present in organisms that do not perform photosynthesis. Many members of this protein set, which is designated the "GreenCut"(Merchant et al., Science 2007), appear to be critical for activities that occur in chloroplasts, but have no established function. Experiments will be performed with pre-existing Chlamydomonas (green, unicellular alga) mutants defective for GreenCut proteins, followed by the generation of additional GreenCut mutant strains; these strains will be thoroughly characterized at the biophysical and biochemical levels. This work will have significant intellectual impact with respect to a number of research areas: It will (1) confer functionality on proteins that have no known function but that are associated with the plant and algal green lineages, and that most likely have some activity associated with chloroplast function (directly or indirectly); (2) allow for a better understanding of photosynthetic dynamics and how they are regulated; (3) generate an initial view of the evolution of photosynthetic components and the ways in which they have diverged in the different algal and plant groups.Broader Impact: Understanding photosynthetic dynamics is likely to provide new insights into ecosystem biology, many of which are suffering severe degradation (e.g. the demise of coral reefs is linked to the deterioration of photosynthetic electron transport in the algae that lives inside the animal component of the coral and provides it with fixed carbon). In a broad sense, an in-depth development of this project will generate a better understanding of the interface of photosynthetic organisms with their environment, which in turn will allow researchers to better manage the various ecosystems on the planet. This line of research has also stimulated the development of an undergraduate course called "Photosynthesis; From Basic Mechanisms to Biofuels", which is currently being taught at Stanford University, and has led to the training of postdoctoral fellows, undergraduate students and graduate students. Finally, this project has facilitated both national and international collaborations; with prominent laboratories.