Regulation of hyphal development by protein kinase A, stress-responsive MAP kinases, and calcineurin via transcription factors Sfl1 and Sfl2 in <i>Candida albicans</i>

<i>Candida albicans</i> exists as a commensal yeast in healthy individuals but becomes an invasive pathogen when host immunity is compromised. Its ability to switch between yeast and hyphal forms is crucial for pathogenesis. While the cAMP-protein kinase A (PKA) pathway is essential for hyphal induction <i>in vitro</i>, filamentation occurs independently of PKA during host infection. This study elucidates how the transcriptional regulators Sfl1 and Sfl2 integrate nutritional and stress signals to control morphological transitions. Through site-specific mutagenesis of conserved target sites for protein kinase A, stress-responsive MAP kinases, and the phosphatase calcineurin in Sfl1 and Sfl2, we demonstrate their roles in orchestrating hyphal development. These findings advance our understanding of how <i>C. albicans</i> modulates its morphology in response to host conditions, providing mechanistic insights into the regulatory networks important for both commensal colonization and invasion.