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POSTERS: Molecular plant-microbe interactions

The polyketide synthase VdPKS1 and the transcription factor VdCmr1 are required for pigment production and UV protection in Verticillium dahliae
Steve Klosterman - USDA ARS. Yulin Fang- Beijing Forestry University, Gustavo Hernandez- Hartnell College, Xiaoping Hu- Northwest A&F University, China, Polly Goldman- USDA ARS, Amy Anchieta- USDA ARS, YongLin Wang- Beijing Forestry Univ

Verticillium dahliae is a soilborne fungus that causes vascular wilt diseases on numerous plant species worldwide. The production of darkly melanized microsclerotia is crucial in the disease cycle of V. dahliae, as these structures allow for long-term survival in soil. The biochemical steps of the dihydroxynaphthalene (DHN) melanin biosynthetic pathway, which are conserved among many fungi, were initially characterized in V. dahliae decades ago. In this study, we further characterized DHN melanin regulation genetically by focusing on functional characterization of genes in a pigment biosynthesis-related gene cluster encoded in the V. dahliae genome. Specifically, we explored roles of cluster-specific transcription factor VdCmr1, as well as two other genes within the cluster encoding a polyketide synthase (VdPKS1) and a laccase (VdLac1), enzymes at the initial and endpoint steps in DHN melanin production. VdCmr1 and VdPKS1 are required for melanin production, but neither is required for microsclerotia production. None of the three genes was required for pathogenesis on tobacco and lettuce. Exposure of the mutant VdCmr1 and wild type strains to UV irradiation or high temperature (40oC), reduced survival in the VdCmr1 mutant strain by more than 50%, relative to the wild type strain. Expression profiles revealed that some melanin biosynthetic genes are in part dependent on wild type VdCmr1. These data indicate VdCmr1 is a key regulator of melanin biosynthesis, and that via regulation of melanogenesis, VdCmr1 affects survival of V. dahliae in response to abiotic threats.