KSEF RDE: Misfolded proteins and stress resistance in plants

During adverse environmental conditions (e.g., heat shoc~ ultraviolet, drought and oxidative stress) proteins are damaged, lose their proper 3-dimensional conformation and unfold. Proteins can also unfold because of translational errors or as a result of the incorporation of amino acid analogues. If misfolded proteins accumulate in the cell they can form cytotoxic aggregates. One of the essential functions of the Ubiquitin/26S froteasome £athway (UPP) is to specifically recognize and degrade misfolded proteins, thus helping the cell to cope with various stress conditions. In yeast and mammalian cells, it has been proven that an increased capacity for UPP-dependent protein degradation leads to higher survival rates under various stress treatments. We hypothesized that if there are proteins that control the up-regulation ofUPP activity in plant cells. we can identifY them by isolating gain-of-function mutants that are cross-tolerant to chemicals that promote the accumulation of damaged proteins. We screened a collection of Arabidopsis thaliana lines that overexpress random cDNAs and isolated three lines that are cross-tolerant to the proteasome inhibitor MG132, the amino acid analog L-canavanine, and the oxidative stress inducer methyl viologen. For one of these lines, we have independently conftrmed that the expressed cDNA confers the cross-tolerance. We propose to analyze the molecular mechanisms that lead to this phenotype and to test if this transgene can be used to enhance the environmental stress resistances of crop species that are important for Kentucky agricultme.