Source and sink mechanisms of nitrogen transport and use

Abstract

Contents Summary35I.Introduction35II.Nitrogen acquisition and assimilation36III.Root‐to‐shoot transport of nitrogen38IV.Nitrogen storage pools in vegetative tissues39V.Nitrogen transport from source leaf to sink40VI.Nitrogen import into sinks42VII.Relationship between source and sink nitrogen transport processes and metabolism43VIII.Regulation of nitrogen transport43IX.Strategies for crop improvement44X.Conclusions46Acknowledgements47References47 Summary Nitrogen is an essential nutrient for plant growth. World‐wide, large quantities of nitrogenous fertilizer are applied to ensure maximum crop productivity. However, nitrogen fertilizer application is expensive and negatively affects the environment, and subsequently human health. A strategy to address this problem is the development of crops that are efficient in acquiring and using nitrogen and that can achieve high seed yields with reduced nitrogen input. This review integrates the current knowledge regarding inorganic and organic nitrogen management at the whole‐plant level, spanning from nitrogen uptake to remobilization and utilization in source and sink organs. Plant partitioning and transient storage of inorganic and organic nitrogen forms are evaluated, as is how they affect nitrogen availability, metabolism and mobilization. Essential functions of nitrogen transporters in source and sink organs and their importance in regulating nitrogen movement in support of metabolism, and vegetative and reproductive growth are assessed. Finally, we discuss recent advances in plant engineering, demonstrating that nitrogen transporters are effective targets to improve crop productivity and nitrogen use efficiency. While inorganic and organic nitrogen transporters were examined separately in these studies, they provide valuable clues about how to successfully combine approaches for future crop engineering.

Comparative genome and transcriptome analysis unravels key factors of nitrogen use efficiency in Brassica napus L

“…The hydroponic experiment showed that the root morphologies of the two B. napus genotypes were affected differently: D4‐15 had more root tips and larger root surface area than D2‐1 under N deficient conditions (Figure S1), suggesting that greater plasticity of the root system might contribute to enhanced NupE and NUE in B. napus (Qin et al, ). Besides changes in root architecture, which affects NupE and NutE, such as N assimilation, remobilization of plant N from senescent to newly growing tissues, and alteration of carbohydrate partitioning might also contribute to NUE (Han, Okamoto, Beatty, Rothstein, & Good, ; Tegeder & Masclaux‐Daubresse, ). NR and GS are two of the most important enzymes in N assimilation (Tegeder & Masclaux‐Daubresse, ).…”

“…N uptake capacity, which is determined by influx transporters located on the plasma membranes of root cells, is one of the major determinants of the NupE, in conjunction with an appropriate root architecture that responds to local and systemic N signals (O'Brien et al, 2016;Qin et al, 2019;White, George, Dupuy, et al, 2013). Following uptake by root cells, some nitrate is assimilated within the roots, whilst a larger proportion is translocated to the shoot, where it is first reduced to nitrite by nitrate reductase (NR) in the cytoplasm, then to ammonium by nitrite reductase (NiR) in the plastids, which is metabolized to glutamate (Glu) and glutamine (Gln) by Gln synthetase (GS) and Glu synthase (GOGAT), respectively (Tegeder & Masclaux-Daubresse, 2018;Xu et al, 2012). N assimilation requires both energy and organic carbon (C) which, in the illuminated leaf, are provided by photosynthesis (Nunes-Nesi, Fernie, & Stitt, 2010;Xu et al, 2012).…”

Impact of the Genetic–Environment Interaction on the Dynamic of Nitrogen Pools in Arabidopsis

“…Plants are able to react to these variations thanks to specific NO 3 sensing systems, making this ion one of the most potent signal molecule affecting plant physiology and development [1]. The biochemical mechanisms involved in NO 3 uptake, assimilation and remobilization have been widely studied in order to identify the features that determine the nitrogen use efficiency (NUE) of a plant [2][3][4][5][6]. The effect of low N availability on plant biomass, NO 3 uptake, ion contents and root architecture has been widely investigated [7][8][9][10].…”

Nutrient sink limitation constrains growth in two barley species with contrasting growth strategies

“…Both the efficiency of nutrient acquisition and the efficiency of nutrient utilisation are important for breeders (Santa‐Maria, Moriconi, & Oliferuk, ), such that sink development in addition to source strength is vital for realising improved crop productivity (Burnett et al., ; White et al., ). Regarding the key mineral nutrient nitrogen, nitrogen transporters have been identified as a key target for improving the nitrogen source:sink balance (Tegeder & Masclaux‐Daubresse, ), whilst nitrogen allocation patterns are important for nitrogen use efficiency and yield (Perchlik & Tegeder, ). Additional nutrient storage, in order to build up nutrient reserves for subsequent grain filling, would require larger nutrient sinks—such as increased capacity for expansion growth—to develop during the vegetative growth stage.…”