Characterization of two yeast gene families whose members regulate TTG resistance.
Kangze He, Aaron Yang, Virginia Aberdeen, William Starmer, Scott Erdman
Department of Biology, Syracuse University, 130 College Place, Syracuse, NY, 13244-1220, USA
Triterpene glycosides (TTGs) are membrane disturbing agents produced by many plants, presumably as defense compounds. A chemical functional genomics screen of the nonessential gene deletion set identified 131 strains whose deletion appears to enable cells to grow more rapidly than wild type cells in the presence of a TTG. To better understand the interaction of TTGs with fungal cells and the functions of specific novel gene products that modulate cellular responses to TTGs, we are studying two multigene families in yeast whose members are involved in these activities. Two novel and related serine-threonine protein kinases influence cell growth rate in the presence of TTGs, as their deletion leads to TTG resistance. We epitope tagged one kinase and are presently determining how, when and where it may function in transducing signals caused by TTGs in cell membranes. Epistasis analyses are also underway with other known loci that have TTG phenotypes. Additional studies involve three yeast homologs of synaptotagmins; proteins regulating calcium dependent exocytic and endocytic events at synaptic membranes of neuronal cells. Double mutants among these loci have been made and we are now attempting to construct the triple deletion. These mutants will be tested for growth defects at different temperatures, in the presence or absence of calcium. We are also examining whether these genes function in mating processes such as pheromone receptor delivery/endocytosis or cell-cell fusion.
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