Abstract
BACKGROUND: Leaf curling is an adaptation to drought stress in plants that has received extensive research attention. Previously, an ethyl methane sulfonate (EMS) mutant library was established for the strawberry species Fragaria nilgerrensis, which yielded a curled leaf mutant (CL). The lignin content was significantly higher in this mutant compared with the wild type (WT). The relevant drought resistance indexes indicated that the resistance of CL was enhanced. However, the regulatory mechanisms and network relationships underlying leaf curling and drought stress in CL mutant remain unknown. RESULT IN THIS STUDY: the RNA sequencing data showed ‘Phenylalanine metabolism’ pathway was enriched in CL vs. WT. Subsequently, key transcription factors were identified through correlation analyses and quantitative experiments, and the TF FnZHD9 was shown to play a positive role in leaf curling, drought resistance and lignin accumulation, respectively, via transient and stable genetic transformation. Moreover, FnZHD9 was confirmed to bind to the promoter of lignin synthesis gene FnCCR1 through yeast one-hybrid (Y1H), dual-luciferase (LUC), GUS, and electrophoretic mobility shift assay (EMSA). Furthermore, the protein-protein interactions between FnZHD9 and the drought resistance regulator, FnMYB44, were also presented by yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC). And FnMYB44 enhanced the transcriptional activation activity of FnZHD9 on the FnCCR1 promote through LUC assay. CONCLUSION: The results of this study provided new insights into the complex lignin regulatory network underlying leaf curling and drought stress, as well as novel information that could aid the breeding of F. nilgerrensis with improved drought resistance. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12870-026-08119-3.