Two glutamate synthases regulate nitrogen metabolism and virulence in Verticillium dahliae

Verticillium dahliae is a widely distributed vascular wilt pathogen with a broad host range, infecting over 200 plant species. Nitrogen metabolism is closely associated with fungal growth and pathogenicity, but the role of glutamate synthase-mediated nitrogen assimilation in V. dahliae has not been fully clarified. Here, we examined the functions of two glutamate synthase-encoding genes, VdGogat1 and VdGogat2, in nitrogen metabolism, virulence, and stress adaptation. Deletion of VdGogat1 (ΔVdGogat1) or VdGogat2 (ΔVdGogat2) reduced host colonization and compromised penetration peg formation. The ΔVdGogat1, ΔVdGogat2, and double mutant strain (ΔVdGogat1/2) showed defects in utilizing specific nitrogen sources. VdGogat1 played a major role in ammonium utilization, whereas VdGogat2 contributed more specifically to glutamine metabolism; accordingly, the ΔVdGogat1/2 strain showed a significantly reduced capacity to utilize ammonium. In addition, loss of VdGogat1 enhanced sensitivity to nitrosative stress. Collectively, these findings indicate that VdGogat1 and VdGogat2 contribute to nitrogen utilization, penetration, and full virulence in V. dahliae.