A Cotton Gbvdr5 Gene Encoding a Leucine-Rich-Repeat Receptor-Like Protein Confers Resistance to Verticillium dahliae in Transgenic Arabidopsis and Upland Cotton

Leucine-rich-repeat receptor-like proteins (eLRR-RLPs) play significant roles in plant defense against pathogens and in plant development. Several eLRR-RLP genes such as Ve1, Gbve, and Gbve1 have been reported to confer resistance to Verticillium dahliae. Gbvdr5, a newly discovered RLP gene from V. dahliae-resistant island cotton cultivar H7124, has a short tail as Ve1. There is a cytosine deletion in Gbvdr5 homologous genes at nucleotide position 2765, which is downstream from the initiation codon in all susceptible upland cotton cultivars analyzed. This deletion was found to cause premature termination of the protein, creating a 937 aa product, but the Gbvdr5 protein had the full 1,077 aa. Transient expression analyses indicated that Gbvdr5 is localized on the plasma membrane. Quantitative polymerase chain reaction analysis revealed that the Gbvdr5 gene was activated by SA, MeJA, ABA, and ETH, and it was induced by V. dahliae isolates V991 and DF-CQ-2 in H7124, whereas was unchanged or repressed in susceptible upland cotton Simian 3. Gbvdr5-promoter-driven GUS activity was found mostly in the root tips and stem growing points of transgenic Arabidopsis. Silencing of Gbvdr5 in Verticillium-wilt-resistant cotton H7124 compromised cotton resistance to V. dahliae isolates V991 and BP2. The resistance was verified by transforming the Gbvdr5 gene into Arabidopsis and upland cotton through Agrobacterium-mediated transformation. Overexpression of the Gbvdr5 gene endowed transgenic Arabidopsis with resistance to defoliating isolate V991 and non-defoliating isolate BP2, but it had no effect on either DF-CQ-2 or JR2 of V. dahliae. The transformed cotton also had confirmed resistance to V991 and BP2. More callose deposition, more expression of the defense-related genes PR1 and PR5, and HR-mimic cell death were observed in the transgenic Arabidopsis when inoculated with V. dahliae. This demonstrated that Verticillium-plant interactions may involve some specific ways of recognizing V. dahliae and Gbvdr5 may be a suitable candidate gene for breeding Verticillium-wilt-resistant cotton lines.