Overexpression of Arabidopsis NLP7 improves plant growth under both nitrogen-limiting and -sufficient conditions by enhancing nitrogen and carbon assimilation.

Lin-Hui Yu,Shi-Gui Li,Jie Wu,Hui Tang,Qi-Sheng Zhu,Shi-Mei Wang,Cheng-Bin Xiang,Yu-Ping Wang,Yang Yuan

doi:10.1038/srep27795

Abstract

Nitrogen is essential for plant survival and growth. Excessive application of nitrogenous fertilizer has generated serious environment pollution and increased production cost in agriculture. To deal with this problem, tremendous efforts have been invested worldwide to increase the nitrogen use ability of crops. However, only limited success has been achieved to date. Here we report that NLP7 (NIN-LIKE PROTEIN 7) is a potential candidate to improve plant nitrogen use ability. When overexpressed in Arabidopsis, NLP7 increases plant biomass under both nitrogen-poor and -rich conditions with better-developed root system and reduced shoot/root ratio. NLP7–overexpressing plants show a significant increase in key nitrogen metabolites, nitrogen uptake, total nitrogen content, and expression levels of genes involved in nitrogen assimilation and signalling. More importantly, overexpression of NLP7 also enhances photosynthesis rate and carbon assimilation, whereas knockout of NLP7 impaired both nitrogen and carbon assimilation. In addition, NLP7 improves plant growth and nitrogen use in transgenic tobacco (Nicotiana tabacum). Our results demonstrate that NLP7 significantly improves plant growth under both nitrogen-poor and -rich conditions by coordinately enhancing nitrogen and carbon assimilation and sheds light on crop improvement.

Highlights

The definition of NUE has been defined in various ways, but the simplest is the amount of plant yield in terms of either total biomass or grain yield per unit of applied fertilizer N4,5
Quantitative real-time PCR analysis showed that the transcript levels of other NIN-like protein (NLP) had no significant difference in the NLP7-overexpressing and wild type (WT) plants (Supplementary Fig. S2)
We found that the NLP7-overexpressing plants had higher chlorophyll contents than the mutant and WT plants under different nitrate conditions (Fig. 1c,d)

Summary

Introduction

The definition of NUE has been defined in various ways, but the simplest is the amount of plant yield in terms of either total biomass or grain yield per unit of applied fertilizer N4,5. Overexpression of OsPTR6, a PTR/NRT1 (PEPTIDE TRANSPORTER/ NITRATE TRANSPORTER 1) family gene, in rice increased plant growth at different N conditions but decreased NUE at high ammonium supply[11]. Ectopic expression of maize Dof[1] (ZmDof1) TF in Arabidopsis and rice leads to the up-regulation of multiple genes involved in C-skeleton production and increased N assimilation and plant growth under low-N conditions[21,22]. NIT2, a homologue of the Arabidopsis NIN-like protein (NLP) genes in Chlamydomonas, was reported as a central regulator required for nitrate signaling and assimilation. Mutants of this gene in Chlamydomonas are not able to activate the expression of the genes required for nitrate assimilation, and they are unable to grow on nitrate as the sole N source[25,26]. Our data imply that NLP7 is a potential candidate for improving the N fertilizer use ability of crops

Methods

Results

Conclusion