Genome-wide Analysis of WRKY Transcription Factor Family in Melon (Cucumis Melo L.) and Their Response to Powdery Mildew

The WRKY family is a large group of transcription factors found in higher plants; it plays an important role in many aspects of biological processes. However, there is very little information about this family in melon (Cucumis melo L.). In our research, 57 candidate WRKY genes in the melon genome were identified. According to their structural and phylogenetic features, the 57 CmWRKY genes were classified into three groups, I, II, and III, and the group II was further divided into five subgroups. Group I included 11 members that all have two conservative WRKY domains and a C2H2-type zinc finger motif; Group II contains 41 WRKY gene family members, that all have a WRKY domain and a C2H2-type zinc finger motif. Five members that all have a conservative WRKY domain and a C2HC-type zinc finger motif are classified as Group III. The expression of 16 selected melon WRKY genes was detected by quantitative real-time PCR after sprayed with salicylic acid (SA) or powdery mildew infection. qRT-PCR analysis showed that 16 CmWRKY genes exhibited distinct expression patterns upon powdery mildew infection, and the expression levels of nine genes were inhibited, and seven genes were induced. After being sprayed with SA, the expression levels of 11 genes were inhibited, and five genes were induced. The data here provide an important basis for further functional studies of the WRKY gene in melon resistance.