SlTCP14 Positively Regulates Low-Light Tolerance by Increasing Antioxidant Activity and BR Biosynthesis in Tomato

Tomato (Solanum lycopersicum L.) often experiences low-light stress during winter greenhouse cultivation. TCPs are unique transcription factors in higher plants and are involved in plant development and the response to abiotic stress. However, the molecular mechanisms through which TCP transcription factors regulate low-light tolerance in crops are unclear. In this study, we elucidated the molecular regulatory mechanism through which SlTCP14, a class I TCP transcription factor, positively regulates low-light tolerance in tomatoes. Compared with the wild type plants, the OE-SlTCP14 plants presented increased chlorophyll content, photosynthetic capacity, and antioxidant enzyme activity but reduced ROS accumulation, whereas the opposite effects were detected for the CR-SlTCP14 plants (SlTCP14 silencing). SlTCP14 binds to the promoter region of the peroxidase gene SlPER10. Additionally, the levels of brassinosteroids (BRs) and BR biosynthetic intermediates significantly increased in OE-SlTCP14 plants, suggesting that the BR biosynthesis pathway may be involved in the induction of chlorophyll biosynthesis through SlTCP14. The results of this study elucidated the mechanism by which SlTCP14 improves low-light tolerance in tomatoes by increasing antioxidant activity and promoting BR synthesis. Our findings provide a reliable basis for further research on the mechanism underlying low-light tolerance and the selection of low-light-tolerant varieties in tomato.