Genome-wide identification of the cucumber 2-OXOGLUTARATE-DEPENDENT DIOXYGENASE (Cs2OGD) superfamily and functional analysis of CsF3H2 in salt stress response

Soil salinization threatens sustainable agriculture. Cucumber ( Cucumis sativus L.), a globally important vegetable, is highly salt-sensitive. The 2-OXOGLUTARATE-DEPENDENT DIOXYGENASE (2-OGD) superfamily is the second largest superfamily in plants, playing a crucial role in growth, development and stress tolerance. However, its functions in cucumber remain largely unknown. Here, we identified 89 Cs2OGD genes in cucumber genome, classifying them into 3 subfamilies across 28 clades. Collinearity analysis revealed that segmental duplication is the primary driver of family expansion, with the highest homology and conserved in gibberellin metabolic observed in Cucumis melo . Promoter analysis revealed 2,686 cis-acting elements, 53% of which are stress-responsive. Transcription factor (TF) binding analysis indicated that CsDofs were the main TF regulators, targeting 85% members of this family. RNA-seq analysis revealed that five distinct expression patterns (Group I–V) for Cs2OGD genes across cucumber tissues. Further investigation expression of constitutively highly expressed genes (Group I and II) under abiotic stress (heat, cold, salt, drought) and hormone treatments (SA, ABA, GA, MeJA) delineated their response profiles and identified CsF3H2 as a key member regulating salt tolerance. Subcellular localization confirmed CsF3H2 resides in the nucleus and endoplasmic reticulum. Overexpression of CsF3H2 significantly enhanced flavonoid/anthocyanin content, boosted antioxidant enzyme (SOD, CAT, APX) activity, and upregulated expression of antioxidant enzymes ( CsCSD, CsFSD, CsMSD, CsCAT ) and ion homeostasis genes ( CsSOS1, CsNHX, CsHKT ), thereby improving salt tolerance. Taken together, this work provides a comprehensive evolutionary and functional analysis of the Cs2OGD superfamily and identifies a valuable genetic resource for improving crop resilience.