HrTCP20 dramatically enhance drought tolerance of sea buckthorn (Hippophae rhamnoides L). by mediating the JA signaling pathway

Sea buckthorn, an important ecological and economical tree species, have remarkable drought and salt resistance. The plant-specific transcription factor TCPs play important roles in plant growth, development, and stress responses. However, in sea buckthorn, the molecular mechanism of TCP proteins and their involvement in drought stress are unknown. Here, we found that the expression of HrTCP20 was significantly up-regulated in sea buckthorn under drought stress. Overexpression of HrTCP20 in Arabidopsis thaliana showed that the superoxide dismutase (SOD), polyphenol oxidase (POD), and chlorophyll (SPAD) content was significantly increased by 1.37 and 1.35 times. However, the malondialdehyde (MDA) content decreased by 0.51 times. Our studies further confirmed that silencing HrTCP20 by virus-induced gene silencing (VIGS) led to a decrease in the content of defense enzymes, relative water content (RWC), and an increase of relative electrical conductivity (REC). Silencing HrTCP20 also caused the jasmonic acid (JA) content to decrease in the VIGS-treated tree. Interestingly, we found that JA accumulation content and the expression of HrLOX2, an essential enzyme for JA synthesis, was significantly inhibited in HrTCP20-silenced sea buckthorn under drought stress. Yeast two-hybrid analysis also showed that HrTCP20 is directly bound to HrLOX2. Taken together, the HrTCP20 transcription factor was a positive regulator in drought resistance of sea buckthorn. Further, our findings will provide comprehensive insights into the forest tree defence system of drought stress.