The Serine Acetyltransferase (SAT) Gene Family in Tea Plant (Camellia sinensis): Identification, Classification and Expression Analysis under Salt Stress

Cysteine plays a pivotal role in the sulfur metabolism network of plants, intimately influencing the conversion rate of organic sulfur and the plant's capacity to withstand abiotic stresses. In tea plants, the serine acetyltransferase (<i>SAT</i>) genes emerge as a crucial regulator of cysteine metabolism, albeit with a notable lack of comprehensive research. Utilizing Hidden Markov Models, we identified seven <i>CssSATs</i> genes within the tea plant genome. The results of the bioinformatics analysis indicate that these genes exhibit an average molecular weight of 33.22 kD and cluster into three distinct groups. Regarding gene structure, <i>CssSAT1</i> stands out with ten exons, significantly more than its family members. In the promoter regions, cis-acting elements associated with environmental responsiveness and hormone induction predominate, accounting for 34.4% and 53.1%, respectively. Transcriptome data revealed intricate expression dynamics of <i>CssSATs</i> under various stress conditions (e.g., PEG, NaCl, Cold, MeJA) and their tissue-specific expression patterns in tea plants. Notably, qRT-PCR analysis indicated that under salt stress, <i>CssSAT1</i> and <i>CssSAT3</i> expression levels markedly increased, whereas <i>CssSAT2</i> displayed a downregulatory trend. Furthermore, we cloned <i>CssSAT1</i>-<i>CssSAT3</i> genes and constructed corresponding prokaryotic expression vectors. The resultant recombinant proteins, upon induction, significantly enhanced the NaCl tolerance of <i>Escherichia coli</i> BL21, suggesting the potential application of <i>CssSATs</i> in bolstering plant stress resistance. These findings have enriched our comprehension of the multifaceted roles played by <i>CssSATs</i> genes in stress tolerance mechanisms, laying a theoretical groundwork for future scientific endeavors and research pursuits.