A positive regulatory role of the watermelon ClWRKY70 gene for disease resistance in transgenic Arabidopsis thaliana

A pathogen-inducible WRKY cDNA was cloned from the leaves of watermelon (Citrullus lanatus) seedlings 24 h after inoculation with Cladosporium cucumerinum. The deduced protein of the gene, designated as ClWRKY70, was classified as a group III WRKY protein based on its single WRKY domain containing a Cys2HisCys zinc-finger motif. Its Arabidopsis thaliana sequence homologue (AtWRKY70) has been described as playing an important role in the plant defense response. ClWRKY70 gene transcripts were highly accumulated in watermelon by salicylic acid treatment, but not by jasmonic acid. By evaluating target gene expression in transgenic Arabidopsis overexpressing the ClWRKY70 gene, it is suggested that the watermelon WRKY gene may play a positive regulatory role in plant resistance against pathogen attack.