Genomic Analysis of the Trehalose-6-Phosphate Synthase Family Involved in Trehalose Biosynthesis and Drought Response in Morus alba

Drought stress severely limits the growth and productivity of Morus alba, yet the molecular mechanisms underlying its adaptation remain poorly understood. Trehalose, an important osmoprotectant and signaling molecule, plays a key role in plant responses to abiotic stress, and its biosynthesis is primarily regulated by trehalose-6-phosphate synthase (TPS). However, the characteristics and potential functions of TPS genes in M. alba have not been systematically investigated. In this study, we identified 11 TPS genes (MaTPSs) in the M. alba genome and performed comprehensive analyses, including phylogenetic relationships, gene structures, conserved motifs, cis-regulatory elements, and expression profiles. Phylogenetic analysis classified MaTPSs into TPS I and TPS II subfamilies, with closer evolutionary relationships to Populus trichocarpa than to Arabidopsis thaliana. Promoter analysis revealed the presence of multiple stress- and hormone-responsive elements, suggesting their potential involvement in abiotic stress regulation. Physiological measurements showed that drought stress significantly increased trehalose accumulation, with a 1.6-fold increase in leaves and a 2.2-fold increase in roots. Expression profiling further demonstrated that six MaTPS genes were upregulated under drought stress, among which MaTPS4, MaTPS9, MaTPS10, and MaTPS11 exhibited significant induction (approximately 5-, 5-, 8-, and 10-fold, respectively). Correlation analysis further indicated that trehalose accumulation was positively associated with all upregulated MaTPS genes (p < 0.05). Taken together, these results suggest that MaTPS genes may be involved in drought-responsive regulation of trehalose metabolism in M. alba. This study provides a valuable foundation for future functional validation and the genetic improvement of drought tolerance in mulberry.