Genome-wide identification and expression analysis of the TCP genes in Senna tora reveal the regulatory mechanism of their response to MeJA

Teosinte Branched1/Cycloidea/Proliferating cell factor (TCP) genes constitute a unique and small class of transcription factors in plants, and are highly important in hormone response and secondary metabolite accumulation. However, Senna tora L. (S. tora) TCP genes have not been studied. In this study, the whole S. tora TCP genome was analyzed to explore its evolution and function. A protein interaction experiment was conducted to further analyze the involvement of TCP in jasmonic acid (JA) signal transduction. A total of 24 TCP TFs were identified in the S. tora genome, and were divided into 2 classes and 3 subfamilies. We found that 16 StTCP gene pairs with collinearity were distributed on 10 different chromosomes, with only one tandem repeat. The expression profiles at different seed developmental stages and tissue specificity analysis showed that StTCP4.1 and StTCP11 may regulate the synthesis of anthraquinone compounds in S. tora. Gene expression levels determined under methyl jasmonate (MeJA) treatment and gene network correlation analysis showed that StTCP4.1 and StTCP11 may be involved in jasmonic acid (JA) response signaling. In addition, subcellular localization analysis showed that StTCP4.1 and StTCP11 were expressed and elicited their functions in the nucleus. Yeast two-hybrid (Y2H) and luciferase complementation (LCI) assay findings showed that StTCP4.1 could directly interact with StMYC2a. In summary, these findings lay a new foundation for improving understanding on the complex mechanism underlying StTCP function in response to JA-induced signaling pathways and on the regulation of secondary metabolite synthesis in S. tora.