VdOGDH is involved in energy metabolism and required for virulence of Verticillium dahliae

Verticillium dahliae, a soil-borne fungus, can invade plant vascular tissue and cause Verticillium wilt. The enzyme alpha-oxoglutarate dehydrogenase (OGDH), catalyzing the oxidation of alpha-oxoglutarate in the tricarboxylic acid cycle (TCA), is vital for energy metabolism in the fungi. Here, we identified the OGDH gene in V. dahliae (VdOGDH, VDAG_10018) and investigated its function in virulence by generating gene deletion mutants (Delta VdOGDH) and complementary mutants (Delta VdOGDH-C). When the Delta VdOGDH mutants were supplemented with different carbon sources, vegetative growth on Czapek Dox medium was significantly impaired, suggesting that VdOGDH is crucial for vegetative growth and carbon utilization. Conidia of the Delta VdOGDH mutants were atypically rounded or spherical, and hyphae were irregularly branched and lacked typical whorled branches. Mutants Delta VdOGDH-1 and Delta VdOGDH-2 were highly sensitive to H2O2 in the medium plates and had higher intracellular ROS levels. Delta VdOGDH mutants also had elevated expression of oxidative response-related genes, indicating that VdOGDH is involved in response to oxidative stress. In addition, the disruption of VdOGDH caused a significant increase in the expression of energy metabolism-related genes VdICL, VdICDH, VdMDH, and VdPDH and melanin-related genes Vayg1, VdSCD, VdLAC, VT4HR, and VaflM in the Delta VdOGDH mutants; thus, VdOGDH is also important for energy metabolism and melanin accumulation. Cotton plants inoculated with Delta VdOGDH mutants exhibited mild leaf chlorosis and the disease index was lower compared with wild type and Delta VdOGDH-C strains. These results together show that VdOGDH involved in energy metabolism of V. dahliae, is also essential for full virulence by regulating multiple fungal developmental factors.