Genome-wide identification and analysis of SmRR gene family in eggplant (Solanum melongena L.) and their response to abiotic stress and auxin.

BACKGROUND

Response regulator proteins (RRs) are integral components of two-component regulatory systems and play critical roles in cytokinin signaling, regulation of plant growth and development, and responses to biotic and abiotic stresses. While numerous RR families have been identified, comprehensive characterization and functional studies of RR genes in eggplant have not been reported.

RESULTS

In this study, we conducted a genome-wide identification and analysis of RR genes in eggplant. Through Blastp and HMM methods, a total of 32 RRs were identified. Phylogenetic analysis classified all RRs into three categories: type-A, type-B RRs, and PRRs (Pseudo-RRs), while no type-C genes were detected. Gene structure and motif analysis demonstrated similarities within each type. Gene duplication and tandem repeats suggested these mechanisms might have facilitated the expansion of the RR gene family in the eggplant genome. Synteny analysis uncovered 18 syntenic blocks between eggplant and Arabidopsis and 33 between eggplant and tomato. Promoter analysis indicated their potential roles in hormone signaling and stress responses. Tissue expression data showed that 12 genes had no or undetectable expression across 17 tested tissues, while others exhibited significant tissue specificity, with most genes showing higher expression in roots. Dynamic expression of 11 selected RR genes in response to salt, drought stress, and IAA hormone treatment in eggplant seedlings revealed that most genes responded to all three treatments. Notably, SmRR9 exhibited the most profound response to salt stress, SmRR1 and SmRR9 to drought stress, and SmRR5 and SmRR6 to IAA treatment. These four genes were proposed as key candidates for future studies on RR gene functions in abiotic stress responses and hormone signaling pathways.

CONCLUSION

The findings of this study provide a foundation for future research on the functional roles of SmRRs in abiotic stress responses and hormone signaling pathways in eggplant, serving as a guide for improving stress tolerance in eggplant.