Isolation and Characterization of Salicylic Acid Induced Transcription Factor SlWRKY From Tomato

WRKY transcription factors belong to a large family of zinc finger regulatory proteins in higher plants in many biological processes, such as responses to biotic and abiotic stress, plant development and mebabolism. However, cloning,expression and function of WRKY family of tomato are little studied. PCR primers were designed based on the conserved domain of  Solanum tuberosum and Capsicum annuum WRKY transcription factor. The full-length cDNA of WRKY-like gene was cloned from the four-leaf stage tomato using homology-based cloning and RT-PCR methods four hours after inducing by 5mM salicylic acid. Various bioinformatics methods including blastn, ORF Finder, and DNAMAN were used to analyze and predict the feature and possible functions of the novel cDNA sequence. The result showed that SlWRKY is a full-length of the novel gene. Sequence analysis indicated that SlWRKY has one conserved WRKY domain and one zinc finger structure, consisted of 975 nucleotides, and deduced amid acid sequence containing 254 amino acids. For the putative protein, SlWRKY has 83% and 64% similarility with WRKY-like transcription factor of Nicotiana tabacum and Vitis vinifera respectively. The relative high similarity with WRKY transcription factors in other botanic species was found as well. Semi-quantitative RT-PCR demonstrated that the corresponding mRNA of SlWRKY was expressed at a similar level in root, stem and leaf of tomato, and accumulated abundantly 2-8h after treatment upon 5mM salicylic acid. The research indicated that the SlWRKY gene may function in plant development and plays a role in plant tolerance to biotic stress, and it have been found that members of plant WRKY transcription factor families are widely implicated in defense responses. So, due to the potential of biotic and abiotic stress activity, tomato SlWRKY gene can be used to enhance resistance against fungi. Therefore, the functions of the novel gene are valuable for further investigations.

 Keywords: Tomato ; Transcription factor ; WRKY ; Salicylic acid