The Regulatory Subunit of Protein Kinase A (Bcy1) in Candida albicans Plays Critical Roles in Filamentation and White-Opaque Switching but Is Not Essential for Cell Growth

Abstract

The conserved cAMP-dependent protein kinase (PKA) is composed of the regulatory and catalytic subunits and acts as the central component of the cAMP signaling pathway. In the human fungal pathogen <i>Candida albicans</i>, the PKA regulatory subunit Bcy1 plays a critical role in the regulation of cell differentiation and death. It has long been considered that Bcy1 is essential for cell viability in <i>C. albicans</i>. In the current study, surprisingly, we found that Bcy1 is not required for cell growth, and we successfully generated a <i>bcy1/bcy1</i> null mutant in <i>C. albicans</i>. Deletion of <i>BCY1</i> leads to multiple cellular morphologies and promotes the development of filaments. Filamentous and smooth colonies are two typical morphological types of the <i>bcy1/bcy1</i> mutant, which can undergo spontaneous switching between the two types. Cells of filamentous colonies grow better on a number of different culture media and have a higher survival rate than cells of smooth colonies. In addition, deletion of <i>BCY1</i> significantly increased the frequency of white-to-opaque switching on N-acetylglucosamine (GlcNAc)-containing medium. The <i>bcy1/bcy1</i> null mutant generated herein provides the field a new resource to study the biological functions of the cAMP signaling pathway in <i>C. albicans</i>.