The complex subunit VdAP-2α regulates polar growth, ergosterol metabolism, and virulence in Verticillium dahliae.

The normal polar growth and morphogenesis represent fundamental factors in development, reproduction survival and host invasion of phytopathogenic fungi. The heterotetramerized AP-2 complex is widely present in eukaryotes and plays a specific role in clathrin-mediated vesicle formation and transport at the plasma membrane in mammals and plants. However, the functions of AP-2 complex in growth, metabolism and virulence of plant pathogenic fungi remain unclear. In this study, the conserved VdAP-2α subunit was identified in Verticillium dahliae by screening of a T-DNA insertion library. VdAP-2α was significantly induced during the developmental phases of V. dahliae, and its GFP-fused signals exhibited a punctate distribution in cytoplasm and on the plasma membrane. Like the insertional mutant, the deletion of VdAP-2α caused the suppression of radial growth, conidiation and virulence, as well as aggravated formation of melanized microsclerotia. Comparative transcriptomic analysis further elucidated the global regulation of VdAP-2α, including hyphal growth, vesicle transport, redox reactions and metabolic processes. Moreover, the impairment of hyphal polarity disordered chitin distribution, bidirectional conidia germination and hydrophobicity, which were associated with membrane defects caused by the decreasing of membrane-associated ergosterols and intermediates. These results contribute to the understanding of the functional characteristics of the AP-2 complex in filamentous fungi and suggest potential antifungal targets.