| Summary: | Potassium is an essential nutrient for plant growth and productivity of crops. K<sup>+</sup> transporters are important for K<sup>+</sup> uptake and transport in plants. However, information on the function of K<sup>+</sup> transporters and K<sup>+</sup> channels in cotton is limited. The KT/KUP/HAK protein family is essential for a variety of physiological processes in plants, including nutrient acquisition and regulation of development. This study, identified a K<sup>+</sup> transporter gene, GhKT2, expressed in the roots of cotton (Gossypium hirsutum) cv. Liaomian17. The deduced transcript of GhKT2 is highly homologous to Cluster II of KUP/HAK/KT K<sup>+</sup> transporters and is predicted to contain 11 transmembrane domains. GhKT2 has been localized to the plasma membrane, and its transcripts were detected in roots, stems, leaves and shoot apices of cotton seedlings. Consistently, b-glucuronidase (GUS) expression driven by the GhKT2 promoter could be detected in roots, mesophyll cells, and leaf veins in transgenic Arabidopsis. In addition, the expression of GhKT2 was induced by low K<sup>+</sup> stress in cotton roots and pGhKT2::GUS-transgenic Arabidopsis seedlings. The GhKT2-overexpression Arabidopsis lines plants were larger and showed greater K<sup>+</sup> accumulation than the wild type (WT) regardless of K<sup>+</sup> concentration supplied. The net K<sup>+</sup> influx rate, measured by the noninvasive micro-test technique, in root meristem zone of GhKT2-transgenic Arabidopsis lines was significantly greater than that of WT. Taken together, this evidence indicates that GhKT2 may participate in K<sup>+</sup> acquisition from low or high external K<sup>+</sup>, as well as K<sup>+</sup> transport and distribution in plants.
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