The green leaf volatile Z-3-Hexenyl acetate improves drought stress resistance of tea plants via regulating the phenylpropanoid biosynthesis pathway

• Z-3-Hexenyl acetate (Z-3-HAC) enhances drought tolerance in tea plants. • Z-3-HAC reduces MDA and soluble sugar accumulation of tea plant under drought stress. • Genes in phenylpropanoid biosynthesis pathway show tendency to synthesize S-lignin. • F5H was tentatively identified as the pivotal genes involved in S lignin biosynthesis. • AP2/ERF transcription factor is identified as potential regulators of F5H. Drought stress severely restricts the growth, development, and productivity of tea plants. Exogenous application of plant growth-regulating substances had been considered an effective strategy to enhance the drought tolerance of tea plants. Yet, the precise mechanism by which green leaf volatile (GLV) Z-3-Hexenyl Acetate (Z-3-HAC) improves the drought resilience in tea plants remains unclear. In this study, we examined the physiological responses and transcriptomic reprogramming of tea plants subjected to drought stress with or without Z-3-HAC pretreatment (ZD). Physiological measurements showed that Z-3-HAC mitigated drought-induced declines in leaf relative water content and reduced the accumulation of soluble sugars and malondialdehyde (MDA) in tea leaves. Transcriptome profiling revealed that 7425 genes were differentially expressed in response to drought stress and/or Z-3-HAC treatment. In addition, 7828 transcripts corresponding to transcription factors (TFs) and protein kinases from 220 gene families were identified, with RLK-Pelle_DLSV, bHLH, AP2/ERF-ERF, C2H2 , and MYB-related being the most abundant members. Differentially expressed genes in the phenylpropanoid biosynthesis pathway indicated a shift toward syringyl (S) lignin formation. And F5H ( evm.TU. Cha01g0169306 ) was identified as a putative key enzyme contributing to S-unit biosynthesis. Co-expression network analysis further suggested that AP2/ERF-ERF ( evm.TU. Cha07g001700 ) may regulate F5H transcription under ZD treatment, acting as a candidate upstream regulator in lignin biosynthesis. Overall, this study advances our understanding of GLV-mediated drought signaling and highlights Z-3-HAC as a promising natural volatile for enhancing abiotic stress resistance in tea plant and potentially other crop or ornamental species.