Genome-Wide Identification and Expression Pattern Analysis of the Stewartia gemmata WRKY Gene Family Within an Evolutionary Framework

WRKY is one of the major transcription factor (TF) families in plants and is involved in various biological processes. However, studies on WRKY TFs are lacking in Stewartia, an early-diverged genus of Theaceae. This study aims to identify and analyze the WRKY members in S. gemmata, a deciduous tree with horticultural potential. We predicted their potential roles and explored their evolutionary relationships with those in other Theaceae species. Our study identified 87 WRKY genes in S. gemmata, which were classified into three groups (group I, II, and III). Groups I and II-c contained the most SgWRKY genes, a pattern consistently found in the other four Camellia species examined, providing a basis for further investigation into the potential roles of these genes in functioning. In addition, we revealed gene expression patterns in leaves and floral organs with qRT-PCR validation, identifying four SgWRKY genes (SgWRKY24, SgWRKY84, SgWRKY67, and SgWRKY77) that were upregulated in multiple comparisons across flowering stages. Collinearity and selection pressure analyses further supported sequence conservation and the presence of purifying selection among analyzed gene pairs. Cis-acting element prediction and enrichment analyses also suggested that these four SgWRKYs may play roles in plant development, stress responses, and secondary metabolism regulation. Collectively, our findings lay the foundation for further functional genomics of SgWRKY genes and provide insights into the evolution of WRKY TFs in Theaceae.