Identification and localized expression of putative K+/H+ antiporter genes in Arabidopsis

The functions of the Arabidopsis K+/H+ antiporters (KEA) have only been partially determined, and further assessments of their biological roles are needed. In this report, we provide localization and expression analyses of six members of the KEA gene family in Arabidopsis. Promoter-driven beta-glucuronidase activity analyses in transgenic Arabidopsis revealed that all KEAs were detected in the vascular tissues of the plants. In the roots, AtKEA2, 4, 5, and 6 were mainly localized to the steles; in addition, AtKEA4 was also found in the root tips. In the leaves, AtKEA1, 2, and 3 were localized to the leaf veins and petioles, whereas AtKEA4, 5, and 6 were preferentially localized to the trichomes. Furthermore, AtKEA1, 2, 3, 4, and 5 were expressed in the guard cells, but AtKEA6 was not. In the florescent organs, all six AtKEA genes were detected in the sepals; interestingly, AtKEA1 was the only member found in the pollen grains. In accordance with promoter localization, quantitative RT-PCR analyses indicated that AtKEA1 and AtKEA3 were mainly expressed in the shoots, whereas AtKEA2, 4, 5, and 6 were expressed in the entire plant. The expression levels of AtKEA transcripts were affected by K+ deficiency and NaCl or osmotic stress Additionally, AtKEAs were regulated by 2,4-dichlorophenoxyacetic acid, benzyladenine, and sucrose. These results provide important information that will support future research on the function and localization of the putative K+/H+ antiporters in Arabidopsis.