Plant Nitrogen Acquisition Under Low Availability: Regulation of Uptake and Root Architecture.

Takatoshi Kiba,Anne Krapp

doi:10.1093/pcp/pcw052

Abstract

Nitrogen availability is a major factor determining plant growth and productivity. Plants acquire nitrogen nutrients from the soil through their roots mostly in the form of ammonium and nitrate. Since these nutrients are scarce in natural soils, plants have evolved adaptive responses to cope with the environment. One of the most important responses is the regulation of nitrogen acquisition efficiency. This review provides an update on the molecular determinants of two major drivers of the nitrogen acquisition efficiency: (i) uptake activity (e.g. high-affinity nitrogen transporters) and (ii) root architecture (e.g. low-nitrogen-availability-specific regulators of primary and lateral root growth). Major emphasis is laid on the regulation of these determinants by nitrogen supply at the transcriptional and post-transcriptional levels, which enables plants to optimize nitrogen acquisition efficiency under low nitrogen availability.

Highlights

Nitrogen (N) availability is a major factor determining plant growth and productivity
N use efficiency has been defined in multiple ways; in general, it can be divided into two components, N utilization efficiency and N acquisition efficiency
Uptake activity and root architecture are the major determinants of the acquisition efficiency

Summary

Introduction

Nitrogen (N) availability is a major factor determining plant growth and productivity. Organic forms contribute to plant N nutrition in specific habitats such as in boreal ecosystems (Jones and Kielland 2012, Werdin-Pfisterer et al 2012), nitrate and ammonium are the universal forms in most soils In natural soils, their availability is generally low but can be highly variable depending on various factors including soil physical properties, leaching and microbial activity, which often result in the formation of N depletion areas in the soil (Jackson and Caldwell 1993, Miller and Cramer 2004). Uptake activity and root architecture are the major determinants of the acquisition efficiency (reviewed in Glass 2003, Garnett et al 2009, Xu et al 2012) The former is facilitated by influx transporters located on the plasma membrane, and the latter by alterations in growth and development in response to local and systemic N signals (Forde 2014, Krapp et al 2014). We mostly focus on ‘N limitation (sudden complete deprivation, low or growth-limiting concentrations)’ and ‘heterogeneous supply (nutrient patches simulated by split-root)’

Regulation of Uptake

Molecular Basis of Ammonium Uptake

Molecular Basis of Nitrate Uptake

Regulation of Root Architecture Under Low N Availability