OVATE family proteins (OFPs) are plant-specific proteins with a conserved OVATE domain that regulate plant growth and development.  Although OFPs have been studied in several species, their biological functions remain largely unknown in cucumber (Cucumis sativus L.).  This study identified 19 CsOFPs distributed on seven chromosomes in cucumber.  Most CsOFP genes were expressed in reproductive organs, but with different expression patterns.  Ectopic expression of CsOFP12-16c in Arabidopsis resulted in shorter and blunt siliques.  The overall results indicated that CsOFP12-16c regulates silique development in Arabidopsis and may have a similar function in cucumber.

Low temperature and high salinity are the major abiotic stresses that restrict cucumber growth and production, breeding materials with multiple abiotic resistance are in greatly need. Here we investigated the effect of introducing the LOS5 gene, a key regulator of ABA biosynthesis in Arabidopsis thaliana, under the stress-responsive RD29A promoter into cucumber (Cucumis sativus L. cv. S516). We found that T1 RD29A-LOS5 transgenic lines have enhanced tolerance to cold and salt stresses. Specifically, transgenic lines exhibited dwarf phenotypes with reduced leaf number, shorter internode, decreased length of the biggest leaf, fewer female flowers, shorter fruit neck and lower vitamin C (Vc). The increased cold tolerance can be reflected from the significantly decreased cold index, the reduced electrolyte leakage index and the MDA content upon cold treatment as compared to those in the control. This may result from the accumulation of internal ABA, soluble sugars and proline, and the enhanced activities of protective enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the transgenic lines. Under salt treatment, the transgenic lines exhibited increased germination index, vigor index, more lateral roots and increased root fresh weight. Moreover, RD29A-LOS5 transgenic plants displayed quicker responses in salt stress than that in low-temperature stress.