Autophagy Activated by <i>Atg1</i> Interacts With <i>Atg9</i> Promotes Biofilm Formation and Resistance of <i>Candida albicans</i>

Autophagy regulates the development of Candida albicans (C. albicans) biofilms and their sensitivity to antifungals. Atg1, a serine/threonine protein kinase, recruits autophagy-related proteins for autophagosome formation. Atg9, the only transmembrane protein, is phosphorylated by Atg1 during autophagy. The specific roles of Atg1 and Atg9 in biofilm formation and resistance of C. albicans remain unclear. The study used RT-qPCR and Western blotting to assess the correlation between Atg1, Atg9 and biofilm formation, XTT reduction assays to evaluate biofilm formation and antifungal resistance, commercial kits to detect reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and autophagy activity, transmission electron microscopy (TEM) to study the morphological changes, protein-protein interaction (PPI) analysis to analyze the interaction between Atg1 and Atg9. Results demonstrated that Atg1 and Atg9 were highly expressed in biofilms than planktonic cells. Biofilm formation, antifungal resistance, MMP and autophagy activity decreased and ROS increased in atg1Δ/Δ and atg9Δ/Δ. TORC1 inhibition with rapamycin rescued the reduced biofilm formation of atg1Δ/Δ and increased antifungal resistance of atg1Δ/Δ and atg9Δ/Δ. PPI analysis and TEM observation indicated that Atg1 interacted with Atg9, which was certified by RT-qPCR and Western blotting. This study suggested that Atg1 interacts with Atg9, activates the autophagy regulating the formation and sensitivity of C. albicans biofilms.