BackgroundTrehalose-6-phosphate synthase (TPS) is an essential enzyme involved in the production of trehalose, and the genes associated with TPS are crucial for various processes such as growth, development, defense mechanisms, and resistance to stress. However, there has been no documentation regarding the evolution and functional roles of the TPS gene family within Theaceae.ResultsHere, we uncovered the lineage-specific evolution of TPS genes in Theaceae. A total of 102 TPS genes were discovered across ten Theaceae species with sequenced genomes. Consistent with the previous classification, our phylogenetic analysis indicated that the TPS genes in Theaceae can be categorized into two primary subfamilies and six distinct clades (I, II-1, II-2, II-3, II-4, II-5), with clade I containing a greater number of introns compared to those found in clade II. Segmental duplication served as the main catalyst for the evolution of TPS genes within Theaceae, and numerous TPS genes exhibited inter-species synteny among various Theaceae species. Most of the TPS genes were ubiquitously expressed, and expression divergence of TPS paralogous pairs was observed. The cis-acting elements found in TPS genes indicated their involvement in responses to phytohormones and stress.ConclusionThis research enhanced our understanding of the lineage-specific evolution of the TPS gene family in Theaceae and offered important insights for future functional analyses.