Genome-Wide Identification, Characterization, and Expression Analysis of Trehalose Metabolism Genes in Tea Plant (Camellia sinensis) Reveals Their Roles in Response to Heat Stress

Heat stress exacerbated by global warming severely impairs the growth and tea quality of the tea plant (<i>Camellia sinensis</i>). Trehalose is pivotal for regulating plant growth and enhancing stress resistance. However, the molecular characteristics, expression patterns, and regulatory mechanisms of trehalose metabolism genes in tea plants under heat stress remain unclear. Therefore, this study conducted a comprehensive investigation of trehalose metabolism genes in the Tieguanyin tea plant genome. A total of 30 trehalose metabolism genes were identified, including 17 <i>trehalose-6-phosphate synthase</i> (<i>CsTPS</i>), 9 <i>trehalose-6-phosphate phosphatase</i> (<i>CsTPP</i>), and 4 <i>trehalase</i> (<i>CsTRE</i>) genes. These genes were characterized in terms of their chromosomal locations and gene structures; the encoded proteins were characterized in terms of their phylogenetic relationships, conserved motifs, functional domains, physicochemical properties, and subcellular distributions. The results showed that these genes exhibit family-specific structural and functional features, laying a foundation for further functional studies. Collinearity analysis identified 20 homologous gene pairs between tea plants and <i>Arabidopsis thaliana</i>, significantly more than the 3 pairs with <i>Oryza sativa</i>, suggesting a closer evolutionary relationship with <i>A. thaliana</i>. Additionally, five intraspecific duplicated gene pairs were identified, all with Ka/Ks values < 1, indicating they have undergone strong purifying selection during evolution, leading to functional stability. <i>Cis</i>-acting element analysis revealed abundant stress-responsive, light-responsive, and phytohormone-responsive elements in the promoter regions of these trehalose metabolism genes, indicating their potential involvement in tea plant stress resistance regulation. Differential expression analyses under heat stress with exogenous trehalose treatment (CK: control, T: water-sprayed heat stress, TT: 5.0 mM trehalose-sprayed heat stress) identified six differentially expressed genes (DEGs). We further analyzed the expression patterns of these DEGs. Specifically, <i>CsTPS1</i>, <i>CsTPS5</i>, and <i>CsTPS12</i> were increasingly upregulated in CK, T, and TT, respectively, while <i>CsTPP1</i> and <i>CsTPP2</i> were upregulated in TT relative to T. Additionally, <i>CsTRE1</i>, <i>CsTRE2</i>, and <i>CsTRE4</i> showed downregulation in TT compared to T, though they were not classified as DEGs. These findings indicate that exogenous trehalose application modulates trehalose metabolism by promoting <i>CsTPS</i> and <i>CsTPP</i> expression while inhibiting <i>CsTRE</i> expression, thereby increasing endogenous trehalose content in tea plants under heat stress. Yeast heat stress tolerance assays confirmed that <i>CsTPS1</i>, <i>CsTPS5</i>, <i>CsTPS12</i>, and <i>CsTPP1</i> enhanced yeast survival at 38 °C, verifying their function in improving organismal heat stress tolerance. In conclusion, these results clarify the roles of trehalose metabolism genes in tea plants' heat stress response, demonstrating that exogenous trehalose modulates their expression to increase endogenous trehalose levels. This study provides a theoretical foundation for exploring trehalose-mediated heat stress resistance mechanisms and improving tea plant stress tolerance via genetic engineering.