| Summary: | Tomato is susceptible to chilling injury during cold storage. In this study, we found that low temperature promoted the expression of brassinosteroid (BR) biosynthetic genes in tomato fruits. The overexpression of <i>SlCYP90B3</i> (<i>SlCYP90B3-OE</i>), a key BR biosynthetic gene, alleviated the chilling injury with decreased electrical conductivity and malondialdehyde. In <i>SlCYP90B3-OE</i> tomato fruits, the activities of antioxidant enzymes, including ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), were markedly increased, while the activity of membranous lipolytic enzymes, lipoxygenase (LOX), and phospholipase D (PLD), were significantly decreased when compared with the wild-type in response to cold storage. Furthermore, the expression level of the cold-response-system component, <i>SlCBF1</i>, was higher in <i>SlCYP90B3-OE</i> fruits than in the wild-type fruits. These results indicated that <i>SlCYP90B3</i> might be involved in the chilling tolerance of tomato fruits during cold storage, possibly by regulating the antioxidant enzyme system and <i>SlCBF1</i> expression.
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