Abstract
Parthenocarpy is an important agronomic trait enabling fruit development without fertilization, contributing significantly to stabilizing crop yields under unfavorable pollination conditions. In this study, the non-parthenocarpic cucumber inbred line 'MT' functioned as experimental material. Unpollinated ovaries were treated with a floral dip agent to induce parthenocarpy, and transcriptomic and metabolomic techniques were used to systematically analyze gene expression and metabolic changes before and after treatment. The results demonstrated that the treated ovaries exhibited substantial swelling, with fruit length and diameter reaching 3.02 and 3.12 times that of the control, respectively. Transcriptome analysis identified multiple differentially expressed genes, and enrichment analysis revealed their significant involvement in pathways including "plant hormone signal transduction", "zeatin biosynthesis", and "tryptophan metabolism". Metabolomics analysis further demonstrated elevated levels of active hormones, including auxin (IAA and IBA), gibberellin (GA(4)), and cytokinin (dihydrozeatin and cis-zeatin) in parthenocarpic fruits. Integrated multi-omics analysis and quantitative real-time PCR identified seven candidate genes associated with hormone biosynthesis and signaling, among which CsYUCCA6, CsSAUR51, CsAUX22, CsGA20OX1, CsCKX3, and CsCYP735A2 were highly expressed in strongly parthenocarpic materials, while CsGA2OX1 was highly expressed in non-parthenocarpic materials. Further, Agrobacterium-mediated transient overexpression confirmed the positive regulatory role of CsGA20OX1 in cucumber parthenocarpy. This research elucidates the key molecular mechanisms underlying hormonal regulation of parthenocarpy in cucumber and provides valuable genetic resources and theoretical foundation for breeding high-yield and stable-yield cucumber varieties. This study identifies CsGA20OX1 as a key regulator of parthenocarpy in cucumber, demonstrating its role in promoting fruit set without fertilization through integrated multi-omics and transient overexpression analysis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11032-026-01635-y.