The VdAP-2 Complex β, μ, and σ Subunits Regulate Polar Growth, Ergosterol Metabolism, and Virulence in Verticillium dahliae.

The AP-2 complex is a heterotetrameric complex that mediates polar growth and morphological development and governs development, reproduction, survival and host colonization in phytopathogenic fungi. We previously determined that the AP-2 complex α subunit was essential for growth, metabolism, and pathogenicity in Verticillium dahliae. Building on this, we systematically investigated the functions of its β, μ, and σ subunits. The deletion of these subunits led to radial growth retardation, decreased sporulation and pathogenicity, and promoted melanin accumulation in V. dahliae. Disrupted hyphal polarity resulted in aberrant chitin deposition and cell surface hydrophobicity defects, mechanistically linked to impaired membrane integrity due to compromised ergosterol biosynthesis. Protein-protein interaction assays and transcriptomic profiling confirmed functional cooperativity among these VdAP-2 subunits. These subunits regulate fungal pathogenicity through control of hyphal polarity and ergosterol biosynthesis. Our study not only elucidates the biological functions of the AP-2 complex in V. dahliae but also establishes a molecular foundation for developing novel antifungal therapeutics targeting membrane homeostasis regulation.