Mediator Subunit Med15 Regulates Cell Morphology and Mating in Candida lusitaniae

Candida lusitaniae is an emerging opportunistic pathogenic yeast capable of shifting from yeast to pseudohyphae form, and it is one of the few Candida species with the ability to reproduce sexually. In this study, we showed that a dpp3 Delta mutant, inactivated for a putative pyrophosphatase, is impaired in cell separation, pseudohyphal growth and mating. The defective phenotypes were not restored after the reconstruction of a wild-type DPP3 locus, reinforcing the hypothesis of the presence of an additional mutation that we suspected in our previous study. Genetic crosses and genome sequencing identified an additional mutation in MED15, encoding a subunit of the mediator complex that functions as a general transcriptional co-activator in Eukaryotes. We confirmed that inactivation of MED15 was responsible for the defective phenotypes by rescuing the dpp3 Delta mutant with a wild-type copy of MED15 and constructing a med15 Delta knockout mutant that mimics the phenotypes of dpp3 Delta in vitro. Proteomic analyses revealed the biological processes under the control of Med15 and involved in hyphal growth, cell separation and mating. This is the first description of the functions of MED15 in the regulation of hyphal growth, cell separation and mating, and the pathways involved in C. lusitaniae.

Automated summary

In this study, it was found that a dpp3 Delta mutants of Candida lusitaniae were impaired in cell separation, pseudohyphal growth, and mating. The defective phenotypes were not restored even after wild-type DPP3 locus reconstruction, indicating the presence of an additional mutation, which was identified as MED15. The inactivation of MED15 was confirmed to be responsible for the defective phenotypes and its role in regulating hyphal growth, cell separation, and mating pathways was revealed.