VdERG2 was involved in ergosterol biosynthesis, nutritional differentiation and virulence of Verticillium dahliae

Abstract

The ergosterol biosynthesis pathway plays an important role in model pathogenic bacteria Saccharomyces cerevisiae, but little is known about the biosynthesis of ergosterol in pathogenic fungus Verticillium dahliae. In this study, we identified the VdERG2 gene encoding sterol C-8 isomerase from V. dahliae and investigated its function in virulence by generating gene deletion mutants (ΔVdEGR2) and complemented mutants (C-ΔVdEGR2). Deletion of VdERG2 reduced ergosterol content. The conidial germination rate and conidial yield of ΔVdERG2 decreased significantly, and abnormal conidia were produced. In spite of VdERG2 did not affect the utilization of carbon sources by V. dahliae, but ΔVdERG2 observed a decrease in melanin production when cellulose and pectin were used as sole carbon sources, respectively. The ability of mutants ΔVdERG2 to produce microsclerotia and melanin decreased and the knockout of VdERG2 led to a significant decrease in the expression of microsclerotia and melanin-related genes VaflM, Vayg1, VDH1, VdLAC, VdSCD and VT4HR. In addition, mutants ΔVdEGR2-1 and ΔVdEGR2-2 were very sensitive to congo red (CR), sodium dodecyl sulfate (SDS) and hydrogen peroxide (H2O2) stresses, indicating that VdEGR2 was involved in cell wall and oxidative stress response. The absence of VdERG2 weakened the penetration ability of mycelium on cellophane and affected the growth of mycelium on cellophane. Although ΔVdERG2 could infect cotton, its pathogenicity was significantly impaired. These phenotypic defects in ΔVdERG2 could be complemented by reintroduction of a full-length VdERG2 gene. In summary, as a single conservative secretory protein, VdERG2 played a crucial role in ergosterol biosynthesis, nutritional differentiation and virulence in V. dahliae.