Arabidopsis as a New Experimental Platform to Investigate the Function of the Nuclear Pore Protein Tpr in SUMOylation and mRNA export.

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Intellectual merit. The nuclear pore complex (NPC) is the gatekeeper for traffic between the nucleus and the cytoplasm of the cell. The NPC structure and protein content is conserved among eukaryotes. Studies of the NPC in several eukaryotic organisms suggest that the long coiled-coil Tpr protein has an important role in mRNA export. Dr. Meier has identified an allelic series of three mutants of the Arabidopsis Tpr gene which show a concomitant increase in severity of three phenotypes i.e. early flowering, Increased SUMOylated protein accumulation, and nuclear accumulation of poly(A)+ RNA. SUMOylation is a post-translational modification of proteins with the polypeptide SUMO. Post-translation modification is a regulatory mechanism that alters the properties of proteins. Dr. Meier has shown that AtTpr and an Arabidopsis SUMO protease interact physically and genetically. Three specific aims will investigate the function of AtTpr at the nuclear pore. They are:1. To show that AtTpr anchors the SUMO protease to the nuclear pore and influences its biological activity;2. To use a proteomics approach to purify AtTpr complexes to determine whether components of the mRNA export machinery are present; 3. To use a genetic screen for suppressors and enhancers of a tpr mutant allele to identify new components connecting flowering time, SUMO homeostasis and mRNA export. This project utilizes the first available multicellular system to study the effects of Tpr mutants on development, likely through the anchoring of nuclear pore-associated activities. Broader Impact. As part of this project, database management, education, and outreach activities will be performed in Dr. Meyer's laboratory. A searchable database for Arabidopsis long coiled-coil proteins ARABI-COIL is widely available to the scientific community listed at TAIR and will be continuously curated. During the past three years, a new bioinformatics module for a plant molecular biology course has been developed and the PI has participated in a local Functional Genomics Summer Course targeting students and faculty from Ohio colleges. These or similar activities will continue in the proposed funding period. The PI is continuously offering an online course for the general public on Plant Biotechnology. Undergraduate students, graduate students and postdocs will be trained and will present their data at national and international meetings, in peer-reviewed publications and in review articles.