Wheat Ammonium Transporter (AMT) Gene Family: Diversity and Possible Role in Host–Pathogen Interaction with Stem Rust

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 <i>TaAMT1;1a, TaAMT1;1b</i>, and <i>TaAMT1;3a</i> were relatively more highly expressed in comparison with other <i>TaAMTs</i>. TaAMT1;1a, TaAMT1;1b, and TaAMT1;3a-GFP were localized in the plasma membrane in tobacco leaves, and <i>TaAMT1;1a, TaAMT1;1b</i>, and <i>TaAMT1;3a</i> successfully complemented a yeast 31019b strain in which ammonium uptake was deficient. In addition, the expression of <i>TaAMT1;1b</i> in an <i>Arabidopsis AMT</i> quadruple mutant (<i>qko</i>) successfully restored [Formula: see text] uptake ability. Resupply of [Formula: see text] rapidly increased cellular [Formula: see text] contents and suppressed expression of <i>TaAMT1;3a</i>, but not of <i>TaAMT;1;1a</i> and <i>TaAMT1;1b</i> expressions. Expression of <i>TaAMT1;1a, TaAMT1;1b</i>, and <i>TaAMT1;3a</i> was not changed in leaves after [Formula: see text] resupply. In contrast, nitrogen (N) deprivation induced <i>TaAMT1;1a, TaAMT1;1b</i>, and <i>TaAMT1;3a</i> 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 <i>TaAMT1;1a, TaAMT1;1b</i>, and <i>TaAMT1;3a</i> 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 [Formula: see text] as the sole N source in the medium after infection with <i>Puccinia graminis</i> f. sp. <i>tritici</i>, suggesting that [Formula: see text] and its transport may facilitate the infection of wheat stem rust disease. Our findings may be important for understanding the potential function <i>TaAMTs</i> in wheat plants.