Sequence and expression analysis of the AMT gene family in poplar

Abstract

Ammonium transporters (AMTs) are plasma membrane proteins that exclusively transport ammonium/ammonia. These proteins are encoded by an ancient gene family with many members. The molecular characteristics and evolutionary history of AMTs in woody plants are still poorly understood. We comprehensively evaluated the AMT gene family in the latest release of the Populus trichocarpa genome (version 3.0; Phytozome 9.0), and identified 16 AMT genes. These genes formed four clusters; AMT1 (7 genes), AMT2 (2 genes), AMT3 (2 genes), and AMT4 (5 genes). Evolutionary analyses suggested that the Populus AMT gene family has expanded via whole-genome duplication events. Among the 16 AMT genes, 15 genes are located on 11 chromosomes of Populus. Expression analyses showed that 14 AMT genes were vegetative organs expressed; AMT1;1/1;3/1;6/3;2 and AMT1;1/1;2/2;2/3;1 had high transcript accumulation level in the leaves and roots, respectively and strongly changes under the nitrogen-dependent experiments. The results imply the functional roles of AMT genes in ammonium absorption in poplar.

Nitrogen Metabolism and Biomass Production in Forest Trees

“…NO 3 - uptake is mediated by a large family of transporters consisting of 68 PtNPF genes encoding nitrate and peptide transporters and a smaller family of 11 PtNRT2/NRT3 genes also encoding nitrate transport systems ( Bai et al, 2013 ). NH 4 + transporters (AMT) are encoded by 22 genes distributed in two separate subfamilies ( AMT1 and AMT2 ) ( Couturier et al, 2007 ; Wu et al, 2015 ; Calabrese et al, 2017 ). Interestingly, the number of AMT2 members in poplar is much higher than in Arabidopsis , suggesting differences in the way that these plants incorporate and transport NH 4 + ions ( Castro-Rodríguez et al, 2017 ; Gojon, 2017 ).…”

An animal homolog of plant Mep/Amt transporters promotes ammonia excretion by the anal papillae of the disease vector mosquito,Aedes aegypti

“…The RhGPs have also been implicated in conducting CO 2 across cellular membranes (Soupene et al, 2004;Kustu and Inwood, 2006;Peng and Huang, 2006;Perry et al, 2010). In contrast, evidence suggests that the plant and microorganism Mep/Amts transport NH 4 + (Willmann et al, 2007;Yuan et al, 2009;Gu et al, 2013;Wu et al, 2015). The exact mechanism of transport is the subject of debate; however, one study proposes that AmtB recruits NH 4 + and as the NH 4 + travels further into the channel it is deprotonated yielding NH 3 (Khademi et al, 2004).…”

“…While plants and microorganisms typically scavenge for ammonia in order to incorporate the nitrogen into proteins, animals excrete it as a toxic by-product of metabolic protein breakdown. Members of the methylammonium permease/ammonium transporter (Mep/Amt) family of transporters play a critical role in ammonia uptake by plants and microorganisms (Thornton et al, 2006;Nygaard et al, 2006;Willmann et al, 2007;Gu et al, 2013;Wu et al, 2015). The annotated genomes of vertebrate animals lack Mep/Amt homologs and excretion of ammonia in animals has been linked to members of a related family of glycoproteins, the Rhesus glycoproteins (RhGPs) (Nawata et al, 2007;Braun et al, 2009;Shih et al, 2013).…”

Overexpression of a pine Dof transcription factor in hybrid poplars: A comparative study in trees growing under controlled and natural conditions

“…A family of 16 ammonium transporters (AMTs) has been identified in the P . trichocarpa genome sequence by in silico analysis [55, 56]. The decrease in ammonium uptake in the transgenics could be explained by the regulation of some of these AMT genes in the plants overexpressing Dof5 as previously described [54,57].…”