Characterization of Arabidopsis Peroxins Acting in Matrix Protein Import
Peroxisomes are single membrane-bound organelles that compartmentalize certain metabolic reactions critical to human and plant development. All proteins functioning in the peroxisome must be synthesized in the cytosol and imported posttranslationally. We are studying peroxisomal processes in Arabidopsis, focusing on the import of matrix proteins from the cytosol into the organelle matrix and on the degradation of proteins that become damaged or obsolete after arrival in the peroxisome. Peroxisomal import depends on more than a dozen peroxin proteins, with PEX5 and PEX7 serving as receptors that shuttle proteins bearing a peroxisome-targeting sequence into the organelle. We have employed forward and reverse genetic approaches to isolate Arabidopsis mutants with defects in various peroxins, and we are using these mutants to elucidate the mechanisms and importance of peroxisome biogenesis and function.
The student will characterize Arabidopsis peroxin mutants isolated through forward and reverse genetic screens in physiological (measuring growth responses) and biochemical (Western blotting) assays. The interactions between mutant and wild-type peroxin derivatives will be characterized using the yeast two-hybrid assay, overexpression studies, and double-mutant analyses.
In humans, deficiencies in peroxins underlie the peroxisomal biogenesis disorders, which are frequently lethal in early infancy. Successful completion of these experiments will advance our understanding of peroxisome biogenesis and metabolism in a genetically distinct model system, which will allow the continued refinement of our understanding of these essential organelles.