Genetics, Vol 147, 43-55, Copyright © 1997

INVESTIGATIONS

Characterization of Synthetic-Lethal Mutants Reveals a Role for the Saccharomyces cerevisiae Guanine-Nucleotide Exchange Factor Cdc24p in Vacuole Function and Na(+) Tolerance

W. H. White and D. I. Johnson
Department of Microbiology and Molecular Genetics, Markey Center for Molecular Genetics, University of Vermont, Burlington, Vermont 05405

Cdc24p is the guanine-nucleotide exchange factor for the Cdc42p GTPase, which controls cell polarity in Saccharomyces cerevisiae. To identify new genes that may affect cell polarity, we characterized six UV-induced csl (CDC24 synthetic-lethal) mutants that exhibited synthetic-lethality with cdc24-4(ts) at 23{deg}. Five mutants were not complemented by plasmid-borne CDC42, RSR1, BUD5, BEM1, BEM2, BEM3 or CLA4 genes, which are known to play a role in cell polarity. The csl3 mutant displayed phenotypes similar to those observed with calcium-sensitive, Pet(-) vma mutants defective in vacuole function. CSL5 was allelic to VMA5, the vacuolar H(+)-ATPase subunit C, and one third of csl5 cdc24-4(ts) cells were elongated or had misshapen buds. A cdc24-4(ts) {Delta}vma5::LEU2 double mutant did not exhibit synthetic lethality, suggesting that the csl5/vma5 cdc24-4(ts) synthetic-lethality was not simply due to altered vacuole function. The cdc24-4(ts) mutant, like {Delta}vma5::LEU2 and csl3 mutants, was sensitive to high levels of Ca(2+) as well as Na(+) in the growth media, which did not appear to be a result of a fragile cell wall because the phenotypes were not remedied by 1 M sorbitol. Our results indicated that Cdc24p was required in one V-ATPase mutant and another mutant affecting vacuole morphology, and also implicated Cdc24p in Na(+) tolerance.

This article has been cited by other articles:

				H.-O. Park and E. Bi Central Roles of Small GTPases in the Development of Cell Polarity in Yeast and Beyond Microbiol. Mol. Biol. Rev., March 1, 2007; 71(1): 48 - 96. [Abstract] [Full Text] [PDF]

				D. Gelperin, L. Horton, A. DeChant, J. Hensold, and S. K. Lemmon Loss of Ypk1 Function Causes Rapamycin Sensitivity, Inhibition of Translation Initiation and Synthetic Lethality in 14-3-3-Deficient Yeast Genetics, August 1, 2002; 161(4): 1453 - 1464. [Abstract] [Full Text] [PDF]

				H.-O. Park, P. J. Kang, and A. W. Rachfal Localization of the Rsr1/Bud1 GTPase Involved in Selection of a Proper Growth Site in Yeast J. Biol. Chem., July 19, 2002; 277(30): 26721 - 26724. [Abstract] [Full Text] [PDF]

				T. J. Richman, M. M. Sawyer, and D. I. Johnson Saccharomyces cerevisiae Cdc42p Localizes to Cellular Membranes and Clusters at Sites of Polarized Growth Eukaryot. Cell, June 1, 2002; 1(3): 458 - 468. [Abstract] [Full Text] [PDF]

				J. M. Murray and D. I. Johnson Isolation and Characterization of Nrf1p, a Novel Negative Regulator of the Cdc42p GTPase in Schizosaccharomyces pombe Genetics, January 1, 2000; 154(1): 155 - 165. [Abstract] [Full Text]

				K. Schumacher, D. Vafeados, M. McCarthy, H. Sze, T. Wilkins, and J. Chory The Arabidopsis det3 mutant reveals a central role for the vacuolar H+-ATPase in plant growth and development Genes & Dev., December 15, 1999; 13(24): 3259 - 3270. [Abstract] [Full Text]

				D. I. Johnson Cdc42: An Essential Rho-Type GTPase Controlling Eukaryotic Cell Polarity Microbiol. Mol. Biol. Rev., March 1, 1999; 63(1): 54 - 105. [Abstract] [Full Text] [PDF]

				K. Larsson, F. Bohl, I. Sjostrom, N. Akhtar, D. Strand, B. M. Mechler, R. Grabowski, and L. Adler The Saccharomyces cerevisiae SOP1 and SOP2 Genes, Which Act in Cation Homeostasis, Can Be Functionally Substituted by the Drosophila lethal(2)giant larvae Tumor Suppressor Gene J. Biol. Chem., December 11, 1998; 273(50): 33610 - 33618. [Abstract] [Full Text] [PDF]

				J. W. Zhang, K. J. Parra, J. Liu, and P. M. Kane Characterization of a Temperature-sensitive Yeast Vacuolar ATPase Mutant with Defects in Actin Distribution and Bud Morphology J. Biol. Chem., July 17, 1998; 273(29): 18470 - 18480. [Abstract] [Full Text] [PDF]