Cs-miR397a–CsLACs module regulates resistance to gray blight and anthracnose diseases via lignin biosynthesis in tea plants (Camellia sinensis)

MicroRNA (miRNA)-mediated post-transcriptional regulation plays a critical role in plant responses to pathogens. Although miR397 is an important regulator of physiological processes, little is known about its role in pathogen resistance, especially in woody tea plants. Here, we reported that Cs-miR397a expression was induced by gray blight infection and investigated the role of Cs-miR397a in repressing the expression of laccases ( CsLAC1 and CsLAC23 ) using 5’ RLM-RACE and co-transformation in tobacco. Cs-miR397a exhibits expression patterns opposite to those of CsLACs in response to pathogens. Both CsLAC1 and CsLAC23 were highly expressed in the stem and were localized to the cell membrane. Overexpression of Cs-MIR397a in Arabidopsis reduced the expression of AtLAC2 , AtLAC4 , and AtLAC17 , and decreased lignin deposition in the stems. Cs-MIR397a -overexpressing plants showed increased sensitivity to C. gloeosporioides infection, with increased H 2 O 2 content and significantly decreased F V /F M values, chlorophyll and carotenoid contents, and peroxidase (POD)/superoxide dismutase (SOD) activities compared to wild-type (WT) plants. Antisense oligodeoxynucleotide (AsODN)- CsLAC1 - or AsODN- CsLAC23 -treated leaves showed increased sensitivity to Pseudopestalotiopsis species infection, accompanied by decreased POD and SOD activities. Moreover, AsODN- CsLAC1 - and AsODN- CsLAC23 -treated leaves were more sensitive to C. gloeosporioides infection, with lower POD and SOD activities than those of the controls. These results demonstrated that Cs-miR397a functions as a negative regulator of resistance to fungal pathogens by modulating the expression of CsLACs and lignin biosynthesis. These findings provide guidance for molecular breeding to improve broad-spectrum resistance of tea plants to fungal diseases.