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Temperature stress is a major environmental factor that limits the growth of cucumber (Cucumis sativus L.). Melatonin has been implicated in plant responses to abiotic stress; however, its transcriptional effects on cucumber under high- and low-temperature conditions remain poorly understood. In this study, cucumber seedlings were exposed to 25 °C, 40 °C, or 4 °C, with or without exogenous melatonin treatment at 75 μmol·L−1, and their transcriptional responses were investigated using RNA sequencing (RNA-seq). Both high- and low-temperature treatments caused varying degrees of seedling wilting, whereas this phenotype was partially alleviated by melatonin application. Transcriptome analysis identified 7488 and 3400 differentially expressed genes in response to high and low temperatures, respectively, indicating both shared and temperature-specific transcriptional responses. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that pathways related to plant hormone signal transduction, phenylpropanoid biosynthesis, and protein processing in the endoplasmic reticulum were significantly enriched in multiple comparisons. Further analysis revealed that melatonin treatment altered the expression patterns of several hormone signaling-related genes and transcription factors, including members of the ERF, MYB, WRKY, and bHLH families. Notably, hormone signaling components exhibited distinct transcriptional responses under high- and low-temperature conditions. The expression trends of selected genes determined by quantitative real-time polymerase chain reaction (qRT-PCR) were generally consistent with the RNA-seq results. Collectively, exogenous melatonin application was associated with reduced wilting symptoms and coordinated transcriptional changes in hormone signaling pathways under temperature stress. These findings provide a basis for further elucidating the molecular mechanisms underlying melatonin-mediated temperature adaptation in cucumber seedlings.

Gibberellins (GAs) regulate fruit set and expansion, and their endogenous levels are controlled in part through catabolic inactivation. GA2ox enzymes convert bioactive GAs into inactive forms, but the expression of GA2ox genes during cucumber fruit development has not been characterised in a tissue-resolved manner. Cucumber (Cucumis sativus L.) '9930' fruit were sampled at 0, 7, 14, 21 and 28 days after pollination. The inner fleshy tissue (pulp) and the outer fruit wall (pericarp) were separated, and CsGA2ox2 transcript abundance was quantified by quantitative real-time PCR using the 2^-ΔΔCt method with Actin (LOC101215469) as the internal reference gene. The protein encoded by CsGA2ox2 was characterised in silico, including sequence homology, physicochemical properties, signal peptide and transmembrane prediction, secondary and tertiary structure modelling, phosphorylation site prediction, and annotation of promoter cis-acting elements. CsGA2ox2 was transcribed at every developmental stage examined. Transcript abundance was low at 0 and 7 days after pollination, increased significantly by 21 days after pollination, and was consistently and significantly higher in pulp than in pericarp at all stages examined. The gene encodes a 342-residue protein sharing 71.84%-74.96% amino acid identity with GA2ox homologues of other cucurbits. It is predicted to be an unstable, hydrophilic, non-secretory protein whose secondary structure is dominated by random coils, and its promoter contains abscisic acid-, light- and meristem-responsive cis-acting elements. CsGA2ox2 shows stage- and tissue-specific transcript accumulation during cucumber fruit development, with a marked bias toward the pulp. All protein-level results presented here are computational predictions and provide no direct functional evidence. The data are descriptive and correlative and are intended as a foundation for future functional studies on GA catabolism in Cucurbitaceae fruit development.

Drought stress severely limits crop productivity by impairing water balance, photosynthesis, and oxidative homeostasis. In this study, plant-derived extracts from Psidium guajava, Aloe vera, Allium sativum, and Medicago sativa were evaluated as biostimulants for improving drought tolerance in barley, rice, maize, and cucumber seedlings. Crop-level screening showed pronounced interspecific differences, with cucumber exhibiting the highest recovery of shoot fresh weight (79% of the non-stressed control at 0.1% extract concentration, compared to 39% under drought stress alone). Consequently, cucumber seedlings were selected for detailed physiological and biochemical analyses. Under drought stress, extract-treated plants maintained higher relative water content, preserved PSII efficiency (Fv/Fm), and retained chlorophyll and carotenoid contents compared with drought-stressed controls. Drought-induced oxidative damage, reflected by increased hydrogen peroxide and malondialdehyde, was significantly reduced by extract application. These protective effects were associated with higher activities of key antioxidant enzymes and increased accumulation of ascorbate and glutathione. Integrated analyses using oxidative stress indices and z-score heatmaps revealed coordinated improvements across multiple physiological and biochemical parameters, particularly under prolonged stress. Collectively, the results suggest that selected plant extracts enhance drought tolerance by supporting water status, antioxidant capacity, and photosynthetic stability, supporting their potential use as sustainable biostimulants in drought-resilient crop production systems.