The light-responsive transcription factor SlBBX20 improves low-temperature resistance of Solanum lycopersicum by affecting photosynthetic capacity, antioxidant capacity, and osmotic adjustment.

Expression of SlBBX20 in tomato was significantly induced by low-temperature stress. SlBBX20 plays a positive role for tomato to resistance low-temperature stress. SIBBX20 gene plays an important role in enhancing low-temperature resistance in tomato seedlings. Under normal conditions, overexpression of SIBBX20 increased the net photosynthetic rate and leaf pigment content (chlorophyll a, chlorophyll b, and carotenoids), the expression of the anthocyanin synthase gene (SIDFR), and the content of anthocyanins in tomato, whereas the photosynthetic capacity, the expression of SIDFR, and the content of anthocyanins in VIGS-mediated SlBBX20-silenced materials did not differ significantly from those in the control. Under low-temperature stress, overexpression of SlBBX20 significantly decreased REC, MDA content, ROS level, and starch accumulation, and increased RWC, photosynthetic capacity, antioxidant enzyme activity, anthocyanin content, and soluble sugar content in tomato leaves. In addition, overexpression of SlBBX20 increased the expression of SlDFR, antioxidant enzymes (SlSOD, SlPOD, and SICAT), low-temperature resistance-related genes (SICBF2, SICBF3, and SlWHYI), starch degradation genes (SIAMY), and decrease the expression of starch synthesis genes (SISA2, SIUGD), which improved the antioxidant capacity, reduced the accumulation of starch, and improved the low-temperature tolerance of tomato seedlings. In conclusion, SlBBX20 enhanced tomato low-temperature tolerance by maintaining the photosynthetic capacity of leaves, reducing ROS and starch accumulation, and increasing antioxidant enzymes and soluble sugar content.