Evolutionary classification of ammonium, nitrate, and peptide transporters in land plants

Neil Jjb Von Wittgenstein,Jürgen Ehlting,Barbara J Hawkins,Cuong H Le

doi:10.1186/1471-2148-14-11

Abstract

BackgroundNitrogen uptake, reallocation within the plant, and between subcellular compartments involves ammonium, nitrate and peptide transporters. Ammonium transporters are separated into two distinct families (AMT1 and AMT2), each comprised of five members on average in angiosperms. Nitrate transporters also form two discrete families (NRT1 and NRT2), with angiosperms having four NRT2s, on average. NRT1s share an evolutionary history with peptide transporters (PTRs). The NRT1/PTR family in land plants usually has more than 50 members and contains also members with distinct activities, such as glucosinolate and abscisic acid transport.ResultsPhylogenetic reconstructions of each family across 20 land plant species with available genome sequences were supplemented with subcellular localization and transmembrane topology predictions. This revealed that both AMT families diverged prior to the separation of bryophytes and vascular plants forming two distinct clans, designated as supergroups, each. Ten supergroups were identified for the NRT1/PTR family. It is apparent that nitrate and peptide transport within the NRT1/PTR family is polyphyletic, that is, nitrate and/or peptide transport likely evolved multiple times within land plants. The NRT2 family separated into two distinct clans early in vascular plant evolution. Subsequent duplications occurring prior to the eudicot/monocot separation led to the existence of two AMT1, six AMT2, 31 NRT1/PTR, and two NRT2 clans, designated as groups.ConclusionPhylogenetic separation of groups suggests functional divergence within the angiosperms for each family. Distinct groups within the NRT1/PTR family appear to separate peptide and nitrate transport activities as well as other activities contained within the family, for example nitrite transport. Conversely, distinct activities, such as abscisic acid and glucosinolate transport, appear to have recently evolved from nitrate transporters.

Highlights

Nitrogen uptake, reallocation within the plant, and between subcellular compartments involves ammonium, nitrate and peptide transporters
Functionally characterized Nitrate transporter (NRT) and Ammonium transporter (AMT) [6,21,23,24,25,26,27,28,29,30] were used for BLASTP searches against the annotated proteomes derived from 20 land plant genome sequences and this set was complemented with two green algal species resulting in a total of more than 1,300 plant protein sequences analyzed (Table 1, Additional file 1)
The AMT1, AMT2, and NRT2 transporter classes are encoded by comparably small gene families in most plants ranging from one to 14 members

Summary

Introduction

Reallocation within the plant, and between subcellular compartments involves ammonium, nitrate and peptide transporters. The NRT1/PTR family in land plants usually has more than 50 members and contains members with distinct activities, such as glucosinolate and abscisic acid transport. NH4+ and NO3- uptake from the soil, as well as movement of NH4+ and NO3- throughout the plant, is regulated by current N demand for growth and NRTs are encoded by two distinct gene families (NRT1 and NRT2) that do not share significant overall sequence similarity. Both families perform proton-coupled active transport and have 12 putative transmembrane (TM) domains [5]. The HATS has inducible members von Wittgenstein et al BMC Evolutionary Biology 2014, 14:11 http://www.biomedcentral.com/1471-2148/14/11

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