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

Abstract

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 NH 4 + and Ba 2+ 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. However, K + concentrations as low as 50 μM 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.