Galactinol synthase 1 improves cucumber performance under cold stress by enhancing assimilate translocation

Cucumber (Cucumis sativus L.) predominantly translocates raffinose family oligosaccharides (RFOs) in the phloem and accumulates RFOs in leaves. Galactinol synthase (GolS) catalyzes the critical step of RFO biosynthesis, and determining the functional diversity of multiple GolS isoforms in cucumber is of scientific significance. In this study, we found that all four isoforms of CsGolS in the cucumber genome were upregulated by different abiotic stresses. beta-Glucuronidase staining and tissue separation experiments suggested that CsGolS1 is expressed in vascular tissues, whereas the other three CsGolSs are located in mesophyll cells. Further investigation indicates that CsGolS1 plays double roles in both assimilate loading and stress response in minor veins, which could increase the RFO concentration in the phloem sap and then improve assimilate transport under adverse conditions. Cold-induced minor vein-specific overexpression of CsGolS1 enhanced the assimilate translocation efficiency and accelerated the growth rates of sink leaves, fruits, and whole plants under cold stress. Finally, our results demonstrate a previously unknown response to adverse environments and provide a potential biotechnological strategy to improve the stress resistance of cucumber.

Automated summary

In this study, all four isoforms of CsGolS in cucumber were found to be upregulated by different abiotic stresses. Further investigation revealed that CsGolS1 plays double roles in both assimilate loading and stress response in minor veins, which could improve assimilate transport under adverse conditions. Overexpression of CsGolS1 under cold stress enhanced assimilate translocation efficiency and accelerated growth rates of sink leaves, fruits, and whole plants. These findings demonstrate an unknown response to adverse environments and provide a potential biotechnological strategy to improve stress resistance in cucumber.