csn-miR171b-3p_2 targets CsSCL6-4 to participate in the defense against drought stress in tea plant

Drought stress is a serious natural challenge for tea plants that significantly affects tea yield and quality. miR171s play critical roles in plant stress responses, however, their role in drought stress tolerance in tea plants (Camellia sinensis) is poorly understood. This study experimentally verified the expression patterns of csn-miR171b-3p_2 and its target, scarecrow-like (SCL). We found that csn-miR171b-3p_2 could target and regulate CsSCL6-4 to play an important role in the defense against drought stress in tea plants. CsSCL6-4 is located in the nucleus and is self-activated in vivo. In addition, we obtained 819 putative binding regions of CsSCL6-4 using DNA affinity purification sequencing analysis, which were assigned to 786 different genes, four of which were drought-resistant genes (CsPrx, CsSDR, CsFAD7, and CsCER1). Yeast one-hybrid and dual-luciferase reporter assays revealed that CsSCL6-4 directly promoted the expression of these four drought resistance genes by binding motifs 1/2/3 in their promoter regions. Both overexpression and suppression of CsSCL6-4 proved that CsSCL6-4 participated in the defense against drought stress in tea plants by regulating the expression of CsPrx, CsSDR, CsFAD7, and CsCER1. In addition, suppression of csn-miR171b-3p_2 expression significantly increased the expression of CsSCL6-4 and activated CsSCL6-4-bound gene transcription under drought stress. Therefore, the csn-miR171b-3p_2-CsSCL6-4 module participates in tea plant resistance to drought stress by promoting the expression of drought resistance genes. Our results revealed the function of csn-miR171b-3p_2 in tea plants and provided new insights into the mechanism of tea plant resistance to drought stress.