Abstract
The Arabidopsis genome contains many sequences annotated as encoding H+-coupled cotransporters. Amongthose are the members of the cation:proton antiporter-2 (CPA2) family (or CHX family), predicted to encodeNa+,K+/H+ antiporters. AtCHX17, a member of the CPA2 family, was selected for expression studies, andphenotypic analysis of knockout mutants was performed. AtCHX17 expression was only detected in roots. Thegene was strongly induced by salt stress, potassium starvation, abscisic acid (ABA) and external acidic pH.Using the b-glucuronidase reporter gene strategy and in situ RT-PCR experiments, we have found thatAtCHX17 was expressed preferentially in epidermal and cortical cells of the mature root zones. Knockoutmutants accumulated less Kþ in roots in response to salt stress and potassium starvation compared with thewild type. These data support the hypothesis that AtCHX17 is involved in Kþ acquisition and homeostasis