The role of ammonium transporter (AMT) against salt stress in plants

Abstract

Since NH₄⁺ is one of the most important limiting nitrogen sources for plant growth, ammonium uptake and transport system has particular attention. In plant cells, ammonium transporters (AMTs) are responsible for ammonium uptake and transport. In previous studies, we identified a PutAMT1;1 gene from Puccinellia tenuiflora, which is a monocotyledonous halophyte species that thrives in alkaline soil. The overexpression of PutAMT1;1 in Arabidopsis thaliana enhanced plant growth and increased plant susceptibility to toxic methylammonium (MeA). This transporter might be useful for improving the root to shoot mobilization of MeA (or NH₄⁺). Interestingly, in our other studies, it can be assumed that urease acts on urea to produce NH₄⁺, which may exacerbate salt stress. Overexpression of PutAMT1;1 promoted early root growth after seed germination in transgenic Arabidopsis under salt stress condition. These findings suggest that ammonium transport alleviates ammonia toxicity caused by salt stress. Subcellular localization revealed that PutAMT1;1 is mainly localized in the plasma membrane and the nuclear periphery and endomembrane system of yeast and plant cells. Here, we discuss these recent findings and speculate on the regular dynamic localization of PutAMT1;1 throughout the cell cycle, which may be related to intracellular activity.

Keywords: (); Ammonium transporter (AMT); Arabidopsis thaliana; Green fluorencence protein (GFP).

Figure 1.

Expression and localization of PutAMT1;1 in Arabidopsis and yeast cells. (a) Growth of wild-type and PutAMT1;1 transgenic lines (lines #1, #2, and #3) on salt stress containing medium for 14 d. (b) GFP fusion proteins of PutAMT1;1 expressed in the yeast cells. (a–e) GFP fusion proteins of PutAMT1;1 are localized at the plasma membrane and around the nuclear periphery of yeast. (c) A suggested model for a possible correlation between fluorescence images of PutAMT1;1-GFP localization and cell cycle. All images were made with a TCS SP2 laser-scanning confocal image system (Leica). GFP fluorescence was excited with an argon laser (488 nm). The size of the scale bars is shown directly in the images.