The function of hkt1 in roots is controversial yeast infection for months. constructs keeping the

The function of HKT1 in roots is controversial. Constructs keeping the first in-frame AUG took place only in K+-starved cells, while the uniport was expressed in all conditions. We discuss here that the LY3009104 distributor symport occurs only yeast infection for months in heterologous expression. It is most likely related to the K+ inhibitable na+ uptake process of roots that heterologous systems fail to reproduce. Living cells need to accumulate large amounts of K+ for osmotic and charge balance adjustments. Although, from a chemical point of view, na+ could perform these functions, high na+ concentrations are toxic for many cellular processes, and na+ exclusion from the cell is as crucial as K+ uptake in all types of cells that are growing in yeast infection for months na+-rich media (rodrguez-navarro, 2000). Plant cells follow this universal rule and plant roots have yeast infection for months the function of providing the entire amount of K+ needed by the whole plant, while restricting the movement of na+ to the xylem sap. This restriction prevents the possibly lethal na+ accumulation in leaves that would inevitably follow water evaporation. Regarding na+ tolerance, plants have large vacuoles where na+ can undertake osmotic functions without producing toxic effects (apse et al., 1999; zhang and blumwald, 2001), but the na+ efflux systems are less effective than in animal cells, as a consequence of their adaptation to the oligotrophic conditions yeast infection for months that prevail in many terrestrial environments (benito and rodrguez-navarro, 2003). To comprehend the interactions of plant life with K+ and LY3009104 distributor na+ and exactly how K+ and na+ transfer to and in the plant, a good and wide knowledge of the function of the yeast infection for months K+ and na+ transporters is required. This understanding has been pursued for a long time, but, recently, interest in the herb K+ and na+ transporters has increased because of the technological importance of constructing yeast infection for months crop plants that are more tolerant to salinity. The use of salty water, which prevails in many agricultural conditions, is an important cause of reductions in crop productivity and yeast infection for months a threat to food security (rhoades et al., 1992). Despite all this technological interest, present knowledge about K+ and na+ transporters in plants is LY3009104 distributor still fragmentary and LY3009104 yeast infection for months distributor confusing. The best example of this situation is the HKT1 transporter yeast infection for months of wheat (expression was partially silenced (laurie et al., 2002). However, if the relevant function of HKT1 is usually na+ uptake, it should be possible to express this transporter in a yeast infection for months heterologous system and find the herb function, high-affinity na+ uptake, that is inhibited by low concentrations of K+ (rains and epstein, 1967a, 1967b; garciadebls et al., 2003). Alternatively, HKT1, instead of being involved in root cation uptake (rubio et al., 1996; wang et al., 1998; laurie et al., 2002), could mediate internal na+ fluxes, as the arabidopsis (cdna can result in either a na+ (or K+) uniporter or in a na+-K+ symporter, depending on the constructs used for inserting the cdna into yeast infection for months the yeast expression vector. The symporter was expressed exclusively in K+-starved cells, while the uniporter was also expressed in cells has2 growing yeast infection for months under normal conditions. Because only the uniport function was identified in barley roots, we suspect that the symport function is an artifact of yeast infection for months expressing HKT1 in yeast. Mutational analysis suggests that the artifact may be produced by yeast infection for months a sequence context or secondary structure of the mrna that yeast infection for months is involved in an alternative initiation of translation in the yeast infection for months herb and that the yeast cells do not understand. RESULTS high-affinity na+ uptake in the roots of barley seedlings the roots of yeast infection for months K+-starved barley seedlings exhibit high-affinity na+ uptake that is inhibited by K+ and in no cases stimulated by K+ (rains and epstein, 1967a, 1967b; garciadebls et al., 2003). This high-affinity uptake could not be detected in seedlings with a yeast infection for months normal K+ content (e.G. Grown in the presence of 3 mm K+) and only appeared as a consequence of K+ starvation. In order to learn more about high-affinity na+ uptake, we tackled the study of na+ uptake during the induction period, when the seedlings still had a normal K+ content. The events that describe the evolution of high-affinity na+ fluxes in a typical experiment with barley seedlings grown at yeast infection for months 3 mm K+ and LY3009104 distributor transferred to a K+-free medium are the following (the effects of K+ starvation can be accelerated if the K+-free medium is renewed very frequently in order to keep yeast infection for months K+ permanently at suprisingly low concentrations): (1).