P-356 - Functional Characterization of Polyketide Synthase (PKS) Gene PKS5 in Fusarium oxysporum f. sp. vasinfectum race 4

Abstract Text:
Cotton Fusarium wilt is caused by Fusarium oxysporum f. sp. vasinfectum (Fov), with significant yield losses across the US. While races 1 and 2 are widely responsible for Fusarium wilt of cotton in US, the emergence of race 4 (Fov4), first identified in California, has since spread to New Mexico and Texas. Fov4 exhibits heightened aggression and virulence toward Pima cotton, capable of causing disease in neutral to alkaline soil without nematodes. However, the study on the mechanisms of Fov4 virulence is very limited. Our study investigates the role of polyketide synthase (PKS) genes in Fov4 pathogenesis. Comparative genome analysis of Fov1 and Fov4 identified two PKS genes unique to Fov4. PKS are key enzymes involved in the biosynthesis of one of the most important groups of fungal secondary metabolites, polyketides, often known to play critical roles in fungal development and pathogenicity. This study focuses on the PKS5 in Fov4 virulence via the generation of knockout (ΔPKS5) and disruption (ΔdsPKS5) mutants using a CRISPR/Cas9 system. ΔPKS5 and ΔdsPKS5 showed impaired vegetative growth when grown on congo-red media when compared to the wild-type strain. ΔPKS5 exhibited reduced virulence in causing cotton root rot, accompanied by decreased expression of fusaric acid biosynthesis genes and lower fusaric acid production. The results suggest polyketide produced by PKS5, along with fusaric acid, plays an important role in stress response and virulence of Fov4 in cotton.