Characteristics and Expression Analyses of Trehalose-6-Phosphate Synthase Family in Prunus mume Reveal Genes Involved in Trehalose Biosynthesis and Drought Response

Trehalose and its key synthase (trehalose-6-phosphate synthase, TPS) can improve the drought tolerance of plants. However, little is known about the roles of trehalose and the TPS family in Prunus mume response to drought. In our study, we discovered that the trehalose content in leaf, root, and stem tissues significantly increased in P. mume in response to drought. Therefore, the characteristics and functions of the TPS family are worth investigating in P. mume. We identified nine TPS family members in P. mume, which were divided into two sub-families and characterized by gene structure, promoter elements, protein conserved domains, and protein motifs. We found that the Hydrolase_3 domain and several motifs were highly conserved in Group II instead of Group I. The distinctions between the two groups may result from selective constraints, which we estimated by the d(N)/d(S) (ω) ratio. The ω values of all the PmTPS family gene pairs were evaluated as less than 1, indicating that purity selection facilitated their divergence. A phylogenetic tree was constructed using 92 TPSs from 10 Rosaceae species, which were further divided into five clusters. Based on evolutionary analyses, the five clusters of TPS family proteins mainly underwent varied purity selection. The expression patterns of PmTPSs under drought suggested that the TPS family played an important role in the drought tolerance of P. mume. Combining the expression patterns of PmTPSs and the trehalose content changes in leaf, stem, and root tissues under normal conditions and drought stress, we found that the PmTPS2 and PmTPS6 mainly function in the trehalose biosynthesis in P. mume. Our findings not only provide valuable information about the functions of trehalose and TPSs in the drought response of P. mume, but they also contribute to the future drought breeding of P. mume.