Altered shoot/root Na+ distribution and bifurcating salt sensitivity in Arabidopsis by genetic disruption of the Na+ transporter AtHKT1

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Abstract
Sodium (Na+) is toxic to most plants, but the molecular mechanisms of plant Na+ uptake and distribution remain largely unknown. Here we analyze Arabidopsis lines disrupted in the Na+ transporter AtHKT1. AtHKT1 is expressed in the root stele and leaf vasculature. athkt1 null plants exhibit lower root Na+ levels and are more salt resistant than wild‐type in short‐term root growth assays. In shoot tissues, however, athkt1 disruption produces higher Na+ levels, and athkt1 and athkt1/sos3 shoots are Na+‐hypersensitive in long‐term growth assays. Thus wild‐type AtHKT1 controls root/shoot Na+ distribution and counteracts salt stress in leaves by reducing leaf Na+ accumulation.