UV-B induced expression of wax synthesis gene LbCYP96A15 in leaves of goji plants (Lycium barbarum) to improve powdery mildew resistance

Powdery mildew poses a significant threat affecting goji plant cultivation, resulting in significant economic losses, particularly in low UV-B environments. To clarify the molecular mechanism by which UV-B-induced wax synthesis in leaves affects the resistance of goji powdery mildew, the ‘Ganqi II’ was used as the experimental material, natural light (no filtration, FUV-B) was used as the control, and two treatments were compared: polyethylene film filtration (filtering 48.62%, HUV-B) and glass filtration (filtering 98.33%, NUV-B). Differences in leaf wax load, powdery mildew resistance, and gene expression were analyzed under these treatments, and key genes involved in UV-B-induced wax synthesis were identified and validated through qRT-PCR, bioinformatics analysis, subcellular localization, and tobacco overexpression assays. The results showed that UV-B reduction using polyethylene film and glass decreased the leaf wax load from 90.65 µg/cm2 to 70.53 µg/cm2 and 49.99 µg/cm2, respectively. Concurrently, the incidence of powdery mildew rose from 7.85 to 21.7% and 72.92%, while the disease index increased from 14.21 to 27.23 and 78.40, respectively. Transcriptomic data revealed that 122 differentially expressed genes (DEGs) were significantly enriched in the lipid metabolism pathway, with 26 DEGs specifically associated in the wax synthesis metabolic pathway. Under FUV-B conditions, the expression of LbCYP96A15 was 18.04 times higher than under NUV-B treatment. LbCYP96A15, localized in the endoplasmic reticulum, plays a key role in wax synthesis. Overexpression of LbCYP96A15 in tobacco increased wax load and reduced powdery mildew incidence and disease index compared to the wild type. UV-B radiation enhances resistance to powdery mildew in goji plants by upregulating the expression of the LbCYP96A15 gene, which promotes leaf wax biosynthesis. LbCYP96A15, a key gene localized in the endoplasmic reticulum, plays a critical role in wax synthesis. Its overexpression significantly increases wax load and reduces the incidence of powdery mildew.