Functional identification of G. hirsutum genes for their role in normal plant development and resistance against Verticillium dahliae using virus-induced gene silencing

Virus-induced gene silencing (VIGS) is a reverse genetic tool used to identify the function of individual genes by reducing their expression. Here VIGS was applied to identify the role of four genes in G. hirsutum; Polyphenol Oxidase (GhPPO), Phosphatidylserine Synthase (GhPSS), Anthocyanidin synthase (GhANS), and Anthocyanidin Reductase (GhANR) in verticillium wilt disease occurring in cotton. Silencing of GhPPO and GhPSS showed abnormal leaf growth such as leaf thinning, reduced leaf size, and leaf curling phenotype which indicates their importance in normal leaf development. RT-PCR and qPCR results showed reduced transcript levels of GhPPO, GhPSS, GhANS, and GhANR in TRV inoculated plants. Moreover silencing of four genes in cotton cultivar FM9160, partially resistant to Verticillium wilt disease compromised resistance by infecting with “King isolate” which is a more aggressive defoliating strain of Verticillium dahliae. The reduced mRNA level of GhPPO and GhPSS makes the cotton plants more susceptible approximately 80% and 76% of leaf wilting were observed while in GhANS and GhANR 66% and 62% leaf wilting were shown. In conclusion, this is the first report showing that the cotton gene GhPPO, GhPSS involved in resistance to Verticillium dahliae and have an important role in normal leaf development in G. hirsutum.