ENHANCED GENE CONVERSION AND POSTMEIOTIC SEGREGATION IN PACHYTENE-ARRESTED SACCHAROMYCES CEREVISIAE

Lance S. Davidow ¹ and Breck Byers ¹

¹ Department of Genetics, SK-50, University of Washington, Seattle, Washington 98195

Previous study has demonstrated that incubation of yeast cells of strain AP-1 in sporulation medium at 36° permits them to begin meiosis but that they become arrested at pachytene and undergo enhanced intragenic recombination between ade2 heteroalleles. Tetrad analysis was undertaken to characterize the altered program of meiotic recombination more widely. In one set of experiments, pachytene-arrested cells were permitted to resume sporulation upon transfer to the permissive temperature. In the resulting asci, both postmeiotic segregation and gene conversion were increased several-fold at a number of loci relative to unarrested controls, whereas reciprocal recombination increased two- to threefold. Another set of experiments analyzed the genetic consequences of inducing the pachytene-arrested cells to revert directly to mitotic growth without completion of meiosis. The appearance of homozygous sectors from heterozygous markers revealed that these cells had become committed to appreciable recombination but that reciprocal exchange was less frequent than in normal asci. Taken together, the data indicate that pachytene arrest rendered the cells committed to enhanced recombination upon resumption of sporulation but that most of the crossing over did not occur until release from the arrest. —The genetic basis of pachytene arrest by AP-1 was investigated by mating each of its parents with progeny of strain Y55, which is able to sporulate at 36°. Both of these diploids sporulated at 36°, and asci from the one studied further exhibited 2:2 segregation of the sporulation defect, indicating that pachytene arrest is dependent on a recessive, temperature-sensitive allele at a chromosomal locus.

This article has been cited by other articles:

				F. W. Stahl, H. M. Foss, L. S. Young, R. H. Borts, M. F. F. Abdullah, and G. P. Copenhaver Does Crossover Interference Count in Saccharomyces cerevisiae? Genetics, September 1, 2004; 168(1): 35 - 48. [Abstract] [Full Text] [PDF]

				J. Yochem and R. K. Herman Investigating C. elegans development through mosaic analysis Development, October 15, 2003; 130(20): 4761 - 4768. [Abstract] [Full Text] [PDF]

				N. J. Morey, P. W. Doetsch, and S. Jinks-Robertson Delineating the Requirements for Spontaneous DNA Damage Resistance Pathways in Genome Maintenance and Viability in Saccharomyces cerevisiae Genetics, June 1, 2003; 164(2): 443 - 455. [Abstract] [Full Text] [PDF]

				W. Chen and S. Jinks-Robertson The Role of the Mismatch Repair Machinery in Regulating Mitotic and Meiotic Recombination Between Diverged Sequences in Yeast Genetics, April 1, 1999; 151(4): 1299 - 1313. [Abstract] [Full Text]

				K. M. Kironmai, K. Muniyappa, D. B. Friedman, N. M. Hollingsworth, and B. Byers DNA-Binding Activities of Hop1 Protein, a Synaptonemal Complex Component from Saccharomyces cerevisiae Mol. Cell. Biol., March 1, 1998; 18(3): 1424 - 1435. [Abstract] [Full Text]

				H Friesen, R Lunz, S Doyle, and J Segall Mutation of the SPS1-encoded protein kinase of Saccharomyces cerevisiae leads to defects in transcription and morphology during spore formation. Genes & Dev., September 15, 1994; 8(18): 2162 - 2175. [Abstract] [PDF]

				N. Kleckner, R. Padmore, and D.K. Bishop Meiotic Chromosome Metabolism: One View Cold Spring Harb Symp Quant Biol, January 1, 1991; 56(0): 729 - 743. [Abstract] [PDF]