Mitochondrial Localization of the Yeast Forkhead Factor Hcm1

Regulations and functions of proline utilization in yeast Saccharomyces cerevisiae

The quality of alcoholic beverages strongly depends on the metabolic characteristics of the yeast cells being used. To control the aroma and the taste of alcoholic beverages, as well as the production of ethanol in them, it is thus crucial to select yeast cells with the proper characteristics. Grape must contain a high concentration of proline, an amino acid that can potentially be a useful nitrogen source. However, Saccharomyces cerevisiae cannot utilize proline during the wine-making process, resulting in the elevated levels of proline in wine and consequent negative effects on wine quality. In this article, I review and discuss recent discoveries about the inhibitory mechanisms and roles of proline utilization in yeast. The information can help in developing novel yeast strains that can improve fermentation and enhance the quality and production efficiency of wine.

A forkhead transcription factor contributes to the regulatory differences of pathogenicity in closely related fungal pathogens

Cryptococcus neoformans and its sister species Cryptococcus deuterogattii are important human fungal pathogens. Despite their phylogenetically close relationship, these two Cryptococcus pathogens are greatly different in their clinical characteristics. However, the determinants underlying the regulatory differences of their pathogenicity remain largely unknown. Here, we show that the forkhead transcription factor Hcm1 promotes infection in C. neoformans but not in C. deuterogattii. Monitoring in vitro and in vivo fitness outcomes of multiple clinical isolates from the two pathogens indicates that Hcm1 mediates pathogenicity in C. neoformans through its key involvement in oxidative stress defense. By comparison, Hcm1 is not critical for antioxidation in C. deuterogattii. Furthermore, we identified SRX1, which encodes the antioxidant sulfiredoxin, as a conserved target of Hcm1 in two Cryptococcus pathogens. Like HCM1, SRX1 had a greater role in antioxidation in C. neoformans than in C. deuterogattii. Significantly, overexpression of SRX1 can largely rescue the defective pathogenicity caused by the absence of Hcm1 in C. neoformans. Conversely, Srx1 is dispensable for virulence in C. deuterogattii. Overall, our findings demonstrate that the difference in the contribution of the antioxidant sulfiredoxin to oxidative stress defense underlies the Hcm1-mediated regulatory differences of pathogenicity in two closely related pathogens.