| Categories genes  | Tags growth  root  transporter  root hair  homeostasis  R protein 
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    • OsHKT2;4 rescued the growth defect of a K(+) uptake-deficient yeast mutant
    • The HKT rice gene, named OsHKT2;4, is expressed in several cell types, including root hairs and vascular parenchyma cells
    • The genetically tractable rice (Oryza sativa; background Nipponbare) possesses two predicted K(+)-transporting class II HKT transporter genes, OsHKT2;3 and OsHKT2;4
    • In this study, we have characterized the ion selectivity of the class II rice HKT transporter OsHKT2;4 in yeast and Xenopus laevis oocytes
    • Interestingly, however, K(+) influx in OsHKT2;4-expressing oocytes did not require stimulation by extracellular Na(+), in contrast to other class II HKT transporters
    • Comparative analyses of Ca(2+) and Mg(2+) permeabilities in several HKT transporters, including Arabidopsis thaliana HKT1;1 (AtHKT1;1), Triticum aestivum HKT2;1 (TaHKT2;1), OsHKT2;1, OsHKT2;2, and OsHKT2;4, revealed that only OsHKT2;4 and to a lesser degree TaHKT2;1 mediate Mg(2+) transport
    • Interestingly, cation competition analyses demonstrate that the selectivity of both of these class II HKT transporters for K(+) is dominant over divalent cations, suggesting that Mg(2+) and Ca(2+) transport via OsHKT2;4 may be small and would depend on competing K(+) concentrations in plants
    • K+ transport by the OsHKT2;4 transporter from rice with atypical Na+ transport properties and competition in permeation of K+ over Mg2+ and Ca2+ ions
    • Surprisingly, a subfamily 2 member from rice (Oryza sativa), OsHKT2;4, has been proposed to form cation/K(+) channels or transporters permeable to Ca(2+) when expressed in Xenopus oocytes
    • Further analyses in media containing both Na(+) and K(+) indicated that OsHKT2;4 functions as K(+)-selective transporter at low external Na(+), but transports also Na(+) at high (>10 mm) Na(+) concentrations
    • These data identify OsHKT2;4 as a new functional type in the K(+) and Na(+)-permeable HKT transporter subfamily
    • The rice monovalent cation transporter OsHKT2;4: revisited ionic selectivity
    • laevis oocytes, we found that OsHKT2;4 could rescue the growth of MM281 in Mg(2+)-deficient conditions and induced the Mg(2+) currents in oocytes at millimolar range of Mg(2+)
    • The Rice High-Affinity K(+) Transporter OsHKT2;4 Mediates Mg(2+) Homeostasis under High-Mg(2+) Conditions in Transgenic Arabidopsis.
    • Additionally, overexpression of OsHKT2;4 to Arabidopsis mutant lines with a knockout of AtMGT6, a gene encoding the transporter protein necessary for Mg(2+) adaptation in Arabidopsis, caused the Mg(2+) toxicity to the leaves under the high-Mg(2+) stress, but not under low-Mg(2+) environments
    • Together, our results demonstrated that OsHKT2;4 is a low-affinity Mg(2+) transporter responsible for Mg(2+) transport to aerials in plants under high-Mg(2+) conditions
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