Heterologous expression of an alligatorweed high-affinity potassium transporter gene enhances salinity tolerance in Arabidopsis thaliana.

UNLABELLED: • PREMISE OF THE STUDY: The potassium cation (K(+)), one of the most abundant cations in cells, improves plant tolerance to various abiotic stresses. Alligatorweed (Alternanthera philoxeroides) is well known for its strong capacity to accumulate K(+) The distinctive K(+) accumulation capability of alligatorweed is linked to a high-affinity K(+) transport facilitated by K(+)-uptake transporters (ApKUPs).• METHODS: A putative K(+) transporter gene, ApKUP4, was isolated from alligatorweed using degenerate primers and rapid amplification of cDNA ends (RACE) techniques. Gene expression profiles were performed by quantitative real time PCR and northern blot analysis. Moreover, we introduced ApKUP4 into Arabidopsis to determine its function in improving crop nutrition and NaCl stress tolerance.• KEY RESULTS: ApKUP4 was localized throughout the entire alligatorweed plant, and its expression was stimulated in the stems and roots under K(+) deficiency, osmotic stress, and salinity stress. Northern blot analysis revealed that ApKUP4 was present in all tested organs of transgenic Arabidopsis plants. Compared with the wild type, Arabidopsis plants overexpressing ApKUP4 showed improved growth and K(+) homeostasis. Moreover, ApKUP4 overexpression in Arabidopsis plants enhanced plant tolerance to salinity stress, as evidenced by reduced water loss and ROS generation, associated with enhanced photosynthesis, nutritional status, and enzymatic antioxidants.• CONCLUSIONS: The present study provides direct evidence that the alligatorweed K(+) transporter gene, ApKUP4, contributes to salinity tolerance in transgenic Arabidopsis seedlings, demonstrating the essentiality of potassium homeostasis for plant salinity tolerance.