Systems involved in K+ uptake from diluted solutions in pepper plants as revealed by the use of specific inhibitors

Here the contribution of the HAK1 transporter the AKT1 channel and a putative AtCHX13 homolog to K+ uptake in the high-affinity range of concentrations in pepper plants was examined The limited development of molecular tools in pepper plants precluded a reverse genetics study in this species By contrast in the model plant Arabidopsis thaliana these type of studies have shown that NH4+ and Ba2- may be used as specific inhibitors of the two K+ uptake systems to dissect their contribution in species in which as in pepper specific mutant lines are not available By using these inhibitors together with Na+ and Cs+ the relative contributions of CaHAK1 CaAKT1 and a putative AtCHX13 homolog to K+ acquisition from diluted solutions under different regimens of K- supply were studied The results showed that in plants completely starved of K+ the gene encoding CaHAK1 was highly expressed and this system is a major contributor to K+ uptake Howevel K+ concentrations as low as 50 mu M reduced CaHAK1 expression and the CaAKT1 channel came into play participating together with CaHAK1 in K+ absorption The contribution of a putative AtCHX13 homolog seemed to be low under this low K+ supply but it cannot be ruled out that at higher K+ concentrations this system participates in K+ uptake Studies of this type allow extension of the tools developed in model plants to understand nutrition in important crops (C) 2010 Elsevier GmbH All rights reserved