A Ve homologous gene from Gossypium barbadense, Gbvdr3, enhances the defense response against Verticillium dahliae

The tomato Ve1 gene and several Ve1 homologues are involved in the resistance to Verticillium dahliae. Here, we report on another Ve homologous gene, Gbvdr3, from a Verticillium wilt-resistant cotton cultivar, Gossypium barbadense Hai7124, which has a 3207-bp region that encodes a predicted receptor-like protein. Transient expression analyses indicated that Gbvdr3 is localized in the plasma membrane, and virus-induced gene silencing of Gbvdr3 compromised the resistance of Hai7124 cotton to a defoliating strain of V. dahliae, V991, but not to a non-defoliating strain, BP2. This resistance pattern was further confirmed by over-expression of Gbvdr3 in transgenic Arabidopsis, which significantly elevated the expression of the ethylene-regulated gene GST2, the ethylene- and jasmonic acid-regulated defense-related genes PR3 and PDF1.2, and the salicylic acid-regulated genes PR1 and PR5, but not the PR2 gene. It also triggered the accumulation of hydrogen peroxide and callose at early time points during infection by the V991 defoliating strain. In contrast, elevated accumulation of hydrogen peroxide or callose in Gbvdr3-expressed Arabidopsis leaves was not apparent under infection by the non-defoliating strain, BP2. These results suggested that Gbvdr3 is involved in the resistance to a unique spectrum of defoliating V. dahliae strains.