Peroxisome dynamics - biogenesis and turnover

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The cells that comprise multicellular organisms separate their metabolic functions among various subcellular compartments known as organelles. Peroxisomes are essential organelles that sequester metabolic reactions that are likely to generate oxidative stress. Peroxisomal sequestration of oxidative reactions protects other cellular components from oxidative damage. However, the peroxisome is itself subject to damage from the oxidative reactions that it harbors. The goals of this research are to uncover the mechanisms and triggers that execute peroxisome turnover when peroxisomes are damaged by oxidative stress. The research will be carried out in the model plant Arabidopsis thaliana. The research activities will provide undergraduate and graduate students with interdisciplinary training bridging molecular genetics, cell biology, genomics, bioinformatics, and biochemistry. To extend research experiences to students at institutions without extensive research capacity, the lab will host visiting faculty and undergraduate researchers from nearby primarily undergraduate institutions. To broaden research awareness and participation beyond her own research group, the principal investigator will organize seminar courses on local biology research to introduce freshmen to the excitement of modern biological research using publications written at their home institution coupled with lab tours and meetings with the authors and other scientists. Together, these activities will train and educate graduate and undergraduate students while elucidating how plant peroxisomes are turned over. The specific project goals are to identify and characterize pexophagy, the selective autophagy process by which peroxisomes are degraded when they are damaged or no longer needed by the host cell. Selective autophagy receptors bring the condemned organelle to the autophagy machinery; the first goal of this project is to identify the plant pexophagy receptor(s). Several candidate receptors will be directly tested for a role in pexophagy in plants, and a genetic screen designed to recover mutants with pexophagy defects will be conducted to uncover additional unanticipated components. The second goal is to identify and characterize signals on the peroxisome that are recognized by the pexophagy receptor(s) to promote plant pexophagy. These experiments will determine if ubiquitin at the peroxisome surface is sufficient for pexophagy and will exploit the wealth of mutants and tools developed in prior studies of Arabidopsis peroxisome biogenesis and function. The results of this research will provide a requisite knowledge base for future investigations of organelle dynamics and are expected to facilitate future peroxisome-based improvements in plant metabolism and stress adaptations.