Abstract 2398 Investigating the relationship between early-acting and receptor-recycling peroxins

Peroxisomes are conserved organelles involved in fatty acid beta-oxidation and the metabolism of reactive oxygen species; proteins called peroxins (PEX proteins) guide organelle formation and function. Peroxins can be grouped into three functional categories: early-acting peroxins (PEX3, PEX16, and PEX19) help insert peroxisomal membrane proteins, receptor/docking peroxins help transport cargo into the peroxisomal lumen, and receptor-recycling peroxins (e.g., PEX12) assist in recycling the cargo receptors back to the cytosol. Mutations in peroxins often result in deleterious phenotypes, such as Zellweger spectrum disorder in humans and developmental defects in plants. We are investigating ways to suppress these defects in Arabidopsis. We found that peroxisomal defects of an Arabidopsis pex12 mutant are suppressed by a null mutation in one of the two isoforms of either PEX3 or PEX19. However, a mutation in the third early-acting peroxin, PEX16, enhances pex12 defects. Our understanding of the interactions between these peroxin types, and how the suppression/enhancement occurs, is limited. We are exploring the hypotheses that the suppression results from restored lipid droplet utilization and/or mislocalization of peroxisomal membrane proteins via microscopy, thin-layer chromatography, and immunoblotting. Our goal is to elucidate the mechanisms of suppression and enhancement to understand why impairing different early-acting peroxins has opposing effects on mutants in other peroxin types. Our studies are revealing more information about the interaction between early-acting peroxins and receptor-recycling peroxins and expanding our understanding of peroxisomes in plants and other eukaryotes.