Functional expression of an animal type-Na+-ATPase gene from a marine red seaweed Porphyra yezoensis increases salinity tolerance in rice plants

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Despite lacking Na+-ATPase as a sodium pump in vascular plants, a gene encoding KPA (K+ P-type ATPase), a putative animal type-Na+/K+-ATPase, has been isolated from the marine red alga Porphyra yezoensis and designated PyKPA1. To characterize the properties of PyKPA1 and also to confirm its ability to confer salinity tolerance in land plants, transgenic rice plants were produced that expressed the full-length PyKPA1 cDNA under the control of cauliflower mosaic virus 35S RNA promoter. We observed transcriptional activation of the transgene, plasma membrane-localization of the gene product fused with green fluorescent protein in onion epidermal cells, and Na+-ATPase activity in the plasma membrane fraction from transgenic rice plants, indicating that PyKPA1 was functionally expressed in rice plants. Transgenic lines were examined in terms of growth in salinity stress conditions, resulting in protection from a decrease in biomass, although growth of control rice plants was repressed. These results demonstrate the utility of a red algal animal type-sodium pump for conferring salinity tolerance to land plants.