Transcriptome-wide identification of WRKY family genes and their expression profiling toward salicylic acid in Camellia japonica

The ornamental plant <i>Camellia japonica</i> is widely distributed worldwide and is susceptible to various environmental stresses. The WRKY transcription factor (TF) is an important node of plant tolerance. However, WRKY TFs from <i>C. japonica</i> have not been reported yet. In this study, 48 <i>CjWRKYs</i>, namely, <i>CjWRKY1</i> to <i>CjWRKY48</i>, were identified. Protein structure analysis revealed that CjWRKY proteins contain a highly conserved motif (WRKYGQK) and two variant motifs (WRKYGKK and WRKYGRK). Phylogenetic analysis indicated that the 48 CjWRKYs can be divided into three groups, which are further classified into six subgroups, namely, I-C, II-a, II-b, II-c, II-e, and III, which contain 10, 6, 8, 13, 7, and 4 members, respectively. The expression patterns of 15 <i>CjWRKYs</i> under salicylic acid (SA) treatment were investigated by real-time quantitative PCR (qRT-PCR). Results showed that the 15 <i>CjWRKYs</i> could be induced by SA treatment. This study is the first to screen <i>CjWRKYs</i> and identify the expression profile of <i>CjWRKYs</i> under SA treatment and provides a theoretical basis for analyzing the function of <i>CjWRKY</i> genes to SA stress tolerance in <i>C. japonica</i>.