Expression profiling of the gibberellin 2-oxidase gene CsGA2ox2 (Cucumis sativus L.) reveals stage- and tissue-specific transcript accumulation during fruit development.

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.