NIH Postdoctoral Fellow Rice University Rosharon, Texas
Peroxisomes are multifunctional membrane-bound organelles in most eukaryotes that sequester essential metabolic reactions. In plants, peroxisomes house fatty acid β-oxidation, the glyoxylate cycle, aspects of photorespiration, and the synthesis of some hormones. Many of these vital reactions generate damaging reactive oxygen species (ROS) that also can function as signaling molecules. Peroxisomes also contain antioxidant enzymes to decompose these ROS. Protein damage ensues during plant development or when antioxidant systems are inadequate, requiring additional quality control mechanisms. Peroxisomes house chaperones and proteases, including LON2 (which has both chaperone and proteolytic activity), that can refold or dispose of individual proteins. In addition, obsolete and damaged peroxisomes can be degraded through pexophagy, a specialized form of autophagy. Despite the importance of peroxisomes and their interactions with other key organelles, our understanding of the mechanisms that trigger or prevent plant peroxisome turnover is minimal. Additionally, knowledge of how dysfunctional peroxisomes induce signals to the rest of the cell is in its infancy. Functional peroxisomes are targeted for destruction by overzealous autophagy machinery when Arabidopsis LON2 is dysfunctional, and we are leveraging this finding to elucidate the LON2 function(s) that normally protect Arabidopsis peroxisomes from pexophagy. As a first step towards identifying LON2 substrates, we used proteomic analysis to compare proteins that accumulate when LON2 is dysfunctional in the presence and absence of autophagy. We are coupling our proteomics data with transcriptomic analysis of identical genotypes to unravel transcriptional and post-transcriptional responses. Analysis of this multi-omics landscape will reveal not only LON2 substrates but also the cellular signaling responses that ensue when pexophagy is heightened or prevented.
This research is supported by the NSF (1907069) and the NIH (K99GM146026 and R35GM130338).