24-epibrassinolide enhanced cold tolerance of winter turnip rape ( Brassica rapa L.)

Brassinosteroids (BR) are multifunctional plant hormones that can regulate growth and development and respond to abiotic stresses. In this study, we investigated the effect of one of brassinosteroids – 24- epibrassinolide (EBL) in alleviating of cold tolerance in winter turnip rape. The results showed that EBL pretreatment could reduce the degree of membrane damage by lipid peroxidation, alleviate ROS burst, improve the osmotic potential, stomatal conductance, photosynthetic efficiency, and antioxidant capacity of winter turnip rape under cold treatment. Compared with EBL + 4 °C treatment, EBL + LaCl 3 + 4 °C and EBL + EGTA + 4 °C treatments can significantly increase the degree of membrane lipid damage, reactive oxygen species (ROS) content, decrease the osmotic adjustment and antioxidation ability, reduce photosynthetic efficiency and stomatal conductance in winter turnip rape. RNA-Seq analysis showed that there were 116 differentially expressed genes (DEGs) in EL (EBL + 4 °C) vs. L (4 °C), including 70 up-regulated genes and 46 down-regulated genes. These DEGs play a critical role in regulating various physiological processes in plants, such as photosynthesis, osmotic regulation of biofilm systems, Ca 2+ signal transduction, redox reactions. We selected the 10 DEGs for further qRT-PCR verification and the results were correlated with the results of RNA-sEq. In conclusion, our research demonstrates that BRs play an important role in enhancing cold tolerance of winter turnip rape. Moreover, additionally LaCl 3 and EGTA effects was studied and discussed together with EBL, the results show that Ca 2+ signalling is involved in BRs-induced cold tolerance.