Abstract
The TCP gene family plays essential roles in plant growth, development, and stress responses, yet their evolutionary dynamics and functional characteristics remain poorly understood in Juglandaceae species. Here, we aimed to systematically identify, classify, and characterize TCP genes across three nut-producing Juglandaceae species-Carya illinoinensis, Annamocarya sinensis, and Juglans regia-to elucidate their evolutionary relationships and potential functions in fruit development. We identified 44, 35, and 36 TCP genes in C. illinoinensis, A. sinensis, and J. regia, respectively, and classified them into three subfamilies (PCF, CIN, and CYC/TB1). Physicochemical property analysis revealed that most proteins were hydrophilic but relatively unstable. Conserved motif and gene structure analyses showed strong similarity among closely related members, while promoter regions were enriched with cis-acting elements associated with development, hormone signaling, and stress responses. Chromosomal mapping demonstrated an uneven distribution of TCP genes, with frequent clustering, and synteny analysis indicated strong conservation and gene duplication within and across species. Transcriptome profiling revealed that approximately half of the TCP genes were expressed in fruit tissues, with CIN subfamily members showing preferential expression. qRT-PCR validation further highlighted AsTCP23, CiTCP14, and JrTCP09 as highly expressed during fruit development, suggesting potential regulatory roles in fruit maturation. These findings provide new insights into the evolutionary patterns and functional divergence of TCP genes in Juglandaceae and establish a valuable foundation for future studies on fruit development and genetic improvement. Collectively, these findings advance our understanding of TCP gene evolution and provide potential molecular targets for improving fruit development and nut quality in Juglandaceae crops.