Abstract
Ammonium transporter (AMT) proteins have been reported in many plants, but no comprehensive analysis was performed in wheat. In this study, we identified 23 AMT members (hereafter TaAMTs) using a protein homology search in wheat genome. Tissue-specific expression analysis showed that TaAMT1;1a, TaAMT1;1b, and TaAMT1;3a were relatively more highly expressed in comparison with other TaAMTs. TaAMT1;1a, TaAMT1;1b, and TaAMT1;3a-GFP were localized in the plasma membrane in tobacco leaves, and TaAMT1;1a, TaAMT1;1b, and TaAMT1;3a successfully complemented a yeast 31019b strain in which ammonium uptake was deficient. In addition, the expression of TaAMT1;1b in an Arabidopsis AMT quadruple mutant (qko) successfully restored uptake ability. Resupply of rapidly increased cellular contents and suppressed expression of TaAMT1;3a, but not of TaAMT;1;1a and TaAMT1;1b expressions. Expression of TaAMT1;1a, TaAMT1;1b, and TaAMT1;3a was not changed in leaves after resupply. In contrast, nitrogen (N) deprivation induced TaAMT1;1a, TaAMT1;1b, and TaAMT1;3a gene expressions in the roots and leaves. Expression analysis in the leaves of the stem rust-susceptible wheat line “Little Club” and the rust-tolerant strain “Mini 2761” revealed that TaAMT1;1a, TaAMT1;1b, and TaAMT1;3a were specifically induced in the former but not in the latter. Rust-susceptible wheat plants grown under N-free conditions exhibited a lower disease index than plants grown with as the sole N source in the medium after infection with Puccinia graminis f. sp. tritici, suggesting that and its transport may facilitate the infection of wheat stem rust disease. Our findings may be important for understanding the potential function TaAMTs in wheat plants.
Highlights
In most soils, nitrate (NO−3 ) and ammonium (NH+4 ) represent the major forms of nitrogen (N) uptake in higher plants
To isolate wheat TaAMTs sequences, 10 rice, 6 Arabidopsis, and 3 potato Ammonium transporter (AMT) sequences were used as baits to obtain the amino sequences of AMTs in wheat
In order to understand the evolutionary relationships between TaAMTs and AMTs from other plant species, the amino acid sequences of 10 AMTs from O. sativa, 6 AMTs from A. thaliana, and 3 AMTs from Solanum lycopersicum were collected and aligned
Summary
Nitrate (NO−3 ) and ammonium (NH+4 ) represent the major forms of nitrogen (N) uptake in higher plants. The NH+4 ions accumulate in cells either by direct uptake from the rhizosphere via ammonium transporters (AMTs) or by reduction of NO−3. Glutamine and asparagine have been identified as the major forms of organic N in the xylem and are translocated from the roots to the shoots (Fukumorita and Chino, 1982). NH+4 is an energetically favorable N source, various plants exhibit toxic symptoms in response to high NH+4 concentrations (Britto and Kronzucker, 2002)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call