Abstract
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 Cys family genes in tomato and analyzed the expression of SlCys genes under cold stress. A bioinformatics analysis showed that the SlCys gene promoters were rich in cis-acting elements related to stress response. Transcriptome data analysis and qRT-PCR (real-time fluorescent quantitative polymerase chain reaction) experiments showed that SlCys5 may be the key gene in the Cys gene family for cold tolerance in tomato. After cold stress treatment, the SlCys5-silenced tomato plants were more sensitive to cold stress, and wilting was more severe than in control plants. Thus, SlCys5 is a positive regulator of cold tolerance in tomato. In this study, we elucidated the evolutionary pattern and functional differentiation of the Cys gene family in tomato, deepening our understanding of the regulatory mechanism of cold stress tolerance in plants.