Overexpression of Flavonoid Biosynthesis Gene, ZeF3H, from Zelkova schneideriana Enhanced Plant Tolerance to Chilling Stress

The flavonoid 3′-hydroxylase gene (F3H), in relation to flavonoid biosynthesis, is widely involved in stress tolerance. To understand its contribution to chilling stress, we cloned a ZeF3H gene—1092 bp long and encoding 363 amino acids—from the chilling-tolerant line of Zelkova schneideriana. Under a cold treatment, ZeF3H’s expression level in the Zelkova genotypes was found to be significantly related to its morphological performance, with a correlation coefficient of −0.8735. The ZeF3H gene was introduced into tobacco plants. When subjected to 4 °C for 10 h, the ZeF3H-transgenic tobacco plants performed better and had relatively low electrical leakage and malondialdehyde contents—0.76-fold and 0.70-fold lower than the wild-type plant—and had a high proline content and soluble sugar content—1.40- and 1.20-fold higher than that of the WT plants, respectively. In conclusion, ZeF3H can significantly improve plants’ tolerance to chilling stress and can be a candidate gene for molecular breeding programs.