WRKY transcription factors serve as key regulators in plants, playing important roles in growth and development, secondary metabolism, and stress responses. Here, a comprehensive genome-wide analysis identified 58 WRKY genes (LcWRKYs) in litchi for the first time. All LcWRKY proteins were predicted to be hydrophilic and localized in the nucleus. Phylogenetic analysis classified them into three major groups (Groups I, II, and III), with a pronounced expansion of Group II, which contained 42 members divided into five subgroups. Members within the same phylogenetic clade exhibited highly similar exon–intron structures and conserved motif compositions, indicating strong evolutionary conservation. LcWRKYs were unevenly distributed across the litchi chromosomes, with chromosome 3 showing the highest gene density. Collinearity analysis suggested that both segmental and tandem duplications contributed to the evolutionary expansion of this family. Notably, promoter cis-acting element analysis revealed that LcWRKYs are enriched with light-responsive, hormone-responsive (e.g., ABA, MeJA, SA), and stress-responsive elements, suggesting their potential involvement in integrating light signaling, hormonal pathways, and environmental stress responses. Integrative expression analysis further revealed that multiple LcWRKYs were significantly up-regulated during the middle and late stages of fruit development in cultivars such as ‘Feizixiao’ and ‘Nuomici’. Consistent with these patterns, qRT-PCR validation demonstrated a pronounced induction of four representative genes (LITCHI004628.m1, LITCHI018082.m1, LITCHI021964.m1, and LITCHI030932.m1) at 40 days post-anthesis, followed by gene-specific expression trajectories at later stages, indicating their potential involvement in regulating fruit development, particularly during the mid-developmental stage. Altogether, the results of this study provide insight into the expansion and potential functional diversification of WRKY transcription factors in litchi and identify candidate regulators associated with fruit development, offering valuable targets for future functional studies and genetic improvement.
Wu et al. (Wed,) studied this question.