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>.

观赏植物山茶（Camellia japonica）在全球范围内广泛分布，且易受多种环境胁迫影响。WRKY转录因子（TF）是植物耐受性调控的关键节点。然而，目前尚未有关于山茶（C. japonica）WRKY转录因子的相关报道。本研究共鉴定出48个山茶WRKY基因家族成员（CjWRKYs），编号为CjWRKY1至CjWRKY48。蛋白质结构分析显示，CjWRKY蛋白包含1个高度保守的基序（WRKYGQK）以及2个变异基序（WRKYGKK与WRKYGRK）。系统发育分析表明，这48个CjWRKY可分为3个大类，进一步可划分为6个亚组，分别为I-C、II-a、II-b、II-c、II-e及III，各亚组所含基因数量依次为10、6、8、13、7及4个。本研究采用实时定量聚合酶链反应（qRT-PCR），探究了15个CjWRKY基因在水杨酸（SA）处理下的表达模式。结果显示，这15个CjWRKY基因均可被水杨酸处理诱导表达。本研究首次筛选得到山茶CjWRKY基因家族，并明确了其在水杨酸处理下的表达谱，为解析山茶CjWRKY基因在水杨酸胁迫耐受性中的功能提供了理论依据。