A Gene Cassette <i>Vd276-280</i> in <i>Verticillium dahliae</i> Contains Two Genes that Affect Melanized Microsclerotium Formation and Virulence

<i>Verticillium dahliae</i> is a soilborne phytopathogenic fungus causing Verticillium wilt on hundreds of plant species. Several sequenced genomes of <i>V</i>. <i>dahliae</i> are available, but functional characterization of most genes has just begun. Based on our previous comparison of the transcriptome from the wild-type and Δ<i>VdCf2</i> strains, a significant upregulation of the gene cassette, <i>Vd276-280</i>, in the Δ<i>VdCf2</i> strain was observed. In this study, the functional characterization of the <i>Vd276-280</i> gene cassette was performed. <i>Agrobacterium</i>-mediated knockout of this gene cassette in <i>V. dahliae</i> significantly inhibited conidiation, melanized microsclerotium formation in the mutant strains, and their virulence toward cotton. Furthermore, deletion of individual genes in the <i>Vd276-280</i> gene cassette identified that the disruption of <i>VDAG_07276</i> and <i>VDAG_07280</i> delayed microsclerotium formation, inhibited conidiation, and reduced virulence toward cotton. Our data suggest that <i>VDAG_07276</i> and <i>VDAG_07280</i> in the <i>Vd276-280</i> gene cassette mainly act as positive regulators of development and virulence in <i>V. dahliae</i>.