The VvmiPEP397-VvmiR397-VvLAC14 module regulates salt tolerance in grapevine

Soil salinization poses a significant constraint to the sustainable development of the grape industry. Although miR397 is known to be involved in plant stress responses, its regulatory mechanism in grapevine salt tolerance remains unclear. In this study, we systematically deciphered the role of the VvmiPEP397-VvmiR397-VvLAC14 module in grapevine salt stress responses using transgenic approaches, transcriptome sequencing, and molecular biology techniques. Our results show that salt stress significantly induces VvMIR397 expression. We identified a functional small peptide, VvmiPEP397, from its primary transcript. Exogenous application of this peptide enhanced VvMIR397 expression and improved salt tolerance in grapevine calli and plants. Overexpression of VvmiR397 significantly enhanced salt tolerance in both grapevine and Arabidopsis, whereas silencing its expression increased sensitivity. Transcriptome analysis further identified the laccase gene VvLAC14 as a direct target of VvmiR397. VvmiR397 negatively regulates VvLAC14 expression through transcript cleavage, reducing lignin accumulation. Conversely, VvLAC14 overexpression increased lignin content and compromised salt tolerance, whereas knockdown of VvLAC14 had opposite effects. This study establishes, for the first time in grapevine, a complete regulatory pathway comprising a small peptide, miRNA, and target gene - VvmiPEP397-VvmiR397-VvLAC14 - revealing a novel mechanism by which this module influences salt tolerance through the regulation of lignin metabolism. Our findings provide new targets and a theoretical foundation for salt-tolerant grapevine breeding.