Suppression of Pyruvate Kinase Deletion Phenotypes in Cryptococcus neoformans

Suppression of Pyruvate Kinase Deletion Phenotypes in Cryptococcus neoformans

Jerry Falwell Library, Lower Esbenshade Atrium

The purpose is to identify the factors responsible for allowing Cryptococcus neoformans to successfully utilize carbon via glycolysis after deletion of the pyruvate kinase gene PYK1 to broaden understanding of carbon source utilization in this human pathogen.

Cryptococcus neoformans persists in the central nervous system via the utilization of glucose. In a prior study assessing the role of pyruvate kinase in central nervous system persistence by C. neoformans, we observed the delayed appearance of pyk1∆ colonies on glucose-containing medium. Colonies appeared as one of three different morphotypes: hyphal, pseudohyphal, or yeast. Additionally, thermosensitivity was also observed for all rescue mutants. Increased filamentation and haploid fruiting has been observed with overexpression of STE12 in C. neoformans.² Therefore, the morphological character of these colonies suggests that the gene(s) coding for the rescue of glucose utilization is/are located near the MAT locus of chromosome 5 in the C. neoformans. Due to the spectrum of morphotypes observed for these pyk1∆ rescue mutants, we hypothesize that a partial genome duplication may be responsible for rescue of the pyk1∆ mutant glucose utilization phenotype, and that the likely area of duplication centers around the MAT locus on Chromosome 5. The genetic basis for the glucose utilization phenotype will be assessed using a novel molecular approach. Alterations in ploidy are associated with increased fluconazole resistance in vivo in C. albicans and C. neoformans³. Therefore, comparative sequence analysis will be used to compare gene copy number between various pyk1∆ suppressor strains and the parental strain pyk1∆.