Integrating transcriptome and metabolome analyses to reveal regulatory mechanism of physiological leaf scorch in Ginkgo biloba L.

Physiological leaf scorch is a stress-induced disorder that adversely affects the growth and yield of ginkgo ( Ginkgo biloba L.). The regulatory mechanisms underlying its occurrence remain poorly understood. To elucidate these mechanisms, physiological, metabolomic, and transcriptomic analyses were integrated across five grades of leaf scorch. Results showed that increasing scorch severity led to elevated leaf relative electrolyte leakage, malondialdehyde (MDA), hydrogen peroxide (H 2 O 2 ) and proline contents, while antioxidant enzyme activities rose initially and then declined, indicating progressively aggravated oxidative stress and membrane damage. Metabolomic-transcriptomic integration revealed significant up-regulation of fatty acids/conjugates and down-regulation of flavonoids, with differentially expressed genes (DEGs) co-enriched in the corresponding metabolic pathways. Weighted gene co-expression network analysis (WGCNA) identified key modules correlated with 11 up-regulated fatty acids/conjugates and 24 down-regulated flavonoids. Hub genes within these modules (such as ASR2 , NAC075 , ERF003 , PRR73 , SNG2 , COI1A , GbUGT74E1 ) exhibited opposite regulatory patterns toward the two metabolite classes. Functional validation demonstrated that under PEG-6000-simulated drought stress, GbUGT74E1 -overexpressing ( GbUGT74E1 -OE) tobacco lines exhibited significantly lower relative electrolyte leakage, MDA content, and H₂O₂ content, along with significantly higher free proline content and antioxidant enzyme activities compared with wild-type (WT) lines, as well as 1.05- to 3.52-fold higher contents of various flavonoids. Furthermore, GbUGT74E1 overexpression remodeled hormonal balance, reducing the levels of the growth hormones indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) while increasing the content of the stress hormone abscisic acid (ABA). Consequently, the GbUGT74E1 -OE lines exhibited enhanced drought resistance alongside a dwarf phenotype. Transient overexpression in ginkgo confirmed its conserved role in hormone regulation. These findings systematically delineate the genetic metabolic regulatory networks that drive oxidative damage during leaf scorch, thereby providing a theoretical foundation for stress-resistant breeding and cultivation management in G. biloba . • The key mechanism of the leaf scorch process of ginkgo was revealed by multi-omics analysis. • The interaction networks between key metabolites and hub genes in ginkgo leaf scorch were inferred. • GbUGT74E1 reduced plant height and alleviated leaf scorch symptoms in tobacco under drought stress. • GbUGT74E1 enhanced plant drought resistance by promoting flavonoid accumulation and altering hormone contents.