Identification of Cysteine synthase (Cys) Gene Family in Tomato (Solanum lycopersicum) and Functional of SlCys5 in Cold Stress Tolerance

Sulfur is an intermediate element in plants. It plays an important role in the growth and development of plants. Plant roots absorb sulfate from their external environment and produce cysteine under the catalysis of cysteine synthase. Cysteine is a synthetic precursor of sulfur-containing metabolites and critical molecules including glutathione (GSH), methionine, vitamins, coenzymes, and antioxidants. It also plays a central role in plant stress resistance. In this study, we identified the <i>Cys</i> family genes in tomato and analyzed the expression of <i>SlCys</i> genes under cold stress. A bioinformatics analysis showed that the <i>SlCys</i> gene promoters were rich in <i>cis</i>-acting elements related to stress response. Transcriptome data analysis and qRT-PCR (real-time fluorescent quantitative polymerase chain reaction) experiments showed that <i>SlCys5</i> may be the key gene in the <i>Cys</i> gene family for cold tolerance in tomato. After cold stress treatment, the <i>SlCys5</i>-silenced tomato plants were more sensitive to cold stress, and wilting was more severe than in control plants. Thus, <i>SlCys5</i> is a positive regulator of cold tolerance in tomato. In this study, we elucidated the evolutionary pattern and functional differentiation of the <i>Cys</i> gene family in tomato, deepening our understanding of the regulatory mechanism of cold stress tolerance in plants.