Genome-Wide Identification and Expression Profiling of MYC Transcription Factor Family in Toona sinensis Under Abiotic and Hormonal Stresses

Toona sinensis (Chinese toon) is a valuable forest resource widely used in gastronomy, phytotherapy, and timber production. MYC transcriptional factors are critical to a variety of biological functions. However, the MYC family remains unsystematically characterized in T. sinensis. A total of 18 TsMYC genes were identified in the T. sinensis genome and grouped into six distinct subfamilies according to phylogenetic analysis in this study. This classification was further supported by analyses of gene structure and conserved motifs. Evolutionary analysis revealed that the TsMYC gene family achieved expansion via whole-genome duplication (WGD) and segmental duplication, with these genes experiencing intense purifying selection throughout the evolutionary process. Additionally, 42 cis-acting elements were detected in the promoter regions of TsMYC genes, and the protein–protein interaction (PPI) network demonstrated that MYC2 serves as a central component in the jasmonic acid (JA) signaling pathway. Expression profiling showed that all TsMYC genes except TsMYC17 were highly expressed in leaves. TsMYC genes displayed distinct expression patterns under salt stress and various phytohormone treatments, with TsMYC17 being the only gene consistently upregulated under all conditions. Subcellular localization assays confirmed that TsMYC17 is localized in the nucleus. These findings suggest that TsMYC17 may play a key role in mediating responses to multiple hormonal signals and abiotic stresses. This research lays a foundation for future investigations into the molecular characteristics and biological roles of the TsMYC17 gene.