Genome-wide identification of WRKY members in elephant grass ( Cenchrus purpureus ) and its expression profiling under aluminum stress

Elephant grass ( Cenchrus purpureus ) shows strong aluminum (Al) tolerance, and studying its mechanisms could provide gene resources for the improvement of Al-sensitive species. WRKY transcription factors (TFs) have been extensively studied for their roles in Al stress response, yet their specific functions in elephant grass under Al stress remain uncharacterized. In this study, we identified 174 CpWRKY TFs in elephant grass, among which 170 were mapped to 14 chromosomes, and four to unanchored contigs. Phylogenetic analysis revealed that they were classified into seven subgroups. Gene structures, conserved motifs, and domain distributions showed high similarity within each subgroup, indicating potential functional conservation. Collinearity analysis indicated that segmental duplication was the primary driver of the expansion of the CpWRKY family relative to tandem duplication. During the 24-h Al treatment time-course, transcriptome analysis identified 48 CpWRKY genes that were differentially expressed at least at one time point. Promoter analysis revealed that stress-responsive elements were the most abundant compared with other categories. Protein-DNA and protein-protein interaction network analyses indicated that WRKY TFs in elephant grass may mediate responses to Al stress through antioxidant defense system, organic acid secretion, and hormone signaling pathways. Overall, this work characterizes the CpWRKY TFs in elephant grass and reveals their potential roles in Al response.