CsLOX facilitates glandular trichome development and increases jasmonate in cucumber (Cucumis sativus L.)

Trichomes play crucial roles in plant growth and development, particularly in stress resistance. In cucumber (Cucumis sativus L.), glandular trichomes (GTs) not only synthesize metabolites but also impact the commercial value of fruits. Lipoxygenases (LOXs) are key enzymes in the octadecanoic acid metabolic pathway in plants and were previously reported to synthesize aromatic substances in cucumber. However, whether LOXs are responsible for GT formation and development remains largely unknown. Here, we identified that CsLOX (CsaV3_4G023810) was highly expressed in GTs. Virus induced gene silence (VIGS) assays showed a significant decrease in GT density in TRSV::CsLOX, indicating the role of CsLOX in GT development. Cslox lines generated via the CRISPR-Cas9 system exhibited a remarkable reduction in the number of GTs. Conversely, the number of GTs significantly increased in CsLOX-Overexpressing (CsLOX-OE) lines. These results strongly support that CsLOX is a positive regulator of GT development. Exogenous application of a LOX inhibitor resulted in a greater reduction in GT number in the wild-type (WT), suggesting there are redundant LOXs. Application of methyl jasmonate (MeJA) on Cslox lines increased GT density, implying that CsLOX regulates GT development through jasmonate synthesis pathway. Additionally, JA and OPDA were measured by LC-MS/MS and found to be consistent with GT density in different tissues. The expression levels of several potential GT related genes such as CsGCR1, CsGCR2, and CsTOE1B1 were closely related to GT development by qPCR. Our study provides initial insights into GT development mediated by CsLOX through the jasmonate synthesis pathway, which is of great significance for enhancing the trichome regulatory network and cucumber breeding.