Research in the Olsen Lab currently focuses on several different areas of cell biology in higher plants.
1. Protein targeting
Peroxisomes (see above) are small organelles present in all eukaryotes. All peroxisomal proteins are post-translationally imported based upon targeting signals present in their amino acid sequence. Using a combination of techniques we are investigating the mechanisms of protein transport into peroxisomes. In addition to being an intrinsically interesting basic biological problem, an understanding of protein trafficking in cells is critical as we design strategies to genetically engineer crop plants. The study of peroxisomal protein targeting in plants has widespread applications; it also provides an experimental vehicle to investigate the mistargeting of peroxisomal proteins, which causes many severe neurological disorders in humans.
2. Peroxisomal proteomics
To understand the function of an organelle, one must first understand the functions of the resident proteins. As part of a collaborative project with researchers at Michigan State University and the University of Stavenger, Norway, we performed in-depth proteome analysis of Arabidopsis leaf peroxisomes to identify novel peroxisomal proteins. A total of 150 proteins were identified, 55 of which were novel peroxisomal proteins (Link to publication page). Subsequent analyses have utilized peroxisomes from Arabidopsis plants at different developmental stages, including glyoxysomes from dark grown seedlings and peroxisomes from dark-induced senescent leaves. This approach has already identified novel proteins expressed during these development processes. Our lab is actively pursuing the biochemical and molecular characterization of several classes of proteins identified from the proteomic analysis. Our lab is actively pursuing the biochemical and molecular characterization of several classes of proteins identified in the proteomic analysis. Read more about Peroxisomal proteomics.
Autophagy is a near ubiquitous process that allows cells to survive under stressful conditions by promoting internal recycling. To understand how the autophagy process is regulated in plant cells we have been studying the functions of Arabidopsis autophagy gene homologs. Using multiple techniques including mutant analysis, expression analysis and confocal microscopy we have been able to find unexpected roles for some of these proteins (learn more on the ATG6 project page). Our work continues on additional autophagy proteins including those responsible for the targeted degradation of our favorite organelle, the peroxisome!
4. Another project in the lab is the study of the photorespiratory aminotransferases in Arabidopsis. We have identified several glyoxylate aminotransferases that have specific amino acid substrate requirements, the structural determinants of which are unknown. In collaboration with Dr. Mark Saper in Biophysics, we are studying the three-dimensional crystal structure of these proteins in an effort to understand the molecular mechanisms of the enzymes’ activity.
Together these experiments have generated a “parts list,” allowing for functional characterization of novel plant-specific peroxisomal proteins.