Metabolite Profiling and Network Analysis Reveal Coordinated Changes in Low-N Tolerant and Low-N Sensitive Maize Genotypes under Nitrogen Deficiency and Restoration Conditions.

Arshid Hussain Ganie,Viswanathan Chinnusamy,Altaf Ahmad,Renu Pandey,Muhammad Iqbal,M Nagaraj Kumar

doi:10.3390/plants9111459

Abstract

Nitrogen (N), applied in the form of a nitrogenous fertilizer, is one of the main inputs for agricultural production. Food production is closely associated with the application of N. However, the application of nitrogenous fertilizers to agricultural fields is associated with heavy production of nitrous oxide because agricultural crops can only utilize 30–40% of applied N, leaving behind unused 60–70% N in the environment. The global warming effect of this greenhouse gas is approximately 300 times more than of carbon dioxide. Under the present scenario of climate change, it is critical to maintain the natural balance between food production and environmental sustainability by targeting traits responsible for improving nitrogen-use-efficiency (NUE). Understanding of the molecular mechanisms behind the metabolic alterations due to nitrogen status needs to be addressed. Additionally, mineral nutrient deficiencies and their associated metabolic networks have not yet been studied well. Given this, the alterations in core metabolic pathways of low-N tolerant (LNT) and low-N sensitive (LNS) genotypes of maize under N-deficiency and their efficiency of recovering the changes upon resupplying N were investigated by us, using the GC–MS and LC–MS based metabolomic approach. Significant genotype-specific changes were noted in response to low-N. The N limitation affected the whole plant metabolism, most significantly the precursors of primary metabolic pathways. These precursors may act as important targets for improving the NUE. Limited availability of N reduced the levels of N-containing metabolites, organic acids and amino acids, but soluble sugars increased. Major variations were encountered in LNS, as compared to LNT. This study has revealed potential metabolic targets in response to the N status, which are indeed the prospective targets for crop improvement.

Highlights

Nitrogen (N) is essential for life sustainability
No such significant change was noticed in the low-N tolerant (LNT) genotype in shoot and root length under
This study has revealed that lipid and sterol, like 16:2-Glc-Campesterol and sitosteryl acetate increased in the LNT genotype; while opposite was the case in the low-N sensitive (LNS)

Summary

Introduction

Nitrogen (N) is essential for life sustainability. Some morphological, developmental and reproductive phenomena such as flowering, growth, senescence, oxidation, reduction and allocation of Plants 2020, 9, 1459; doi:10.3390/plants9111459 www.mdpi.com/journal/plantsPlants 2020, 9, 1459 photosynthates in a plant are regulated by the availability of N [1]. Nitrogen (N) is essential for life sustainability. Application of N fertilizers has both positive and negative impacts; it has increased the supply of food, feed and several biobased products remarkably on one hand, and deteriorated the quality of the environment and caused huge economic losses by depleting the fossil-fuel reserves, on the other. Various forms of N released into the environment pose a serious threat to the health of humans, plants and animals [2]. Excessive use of non-sustainable fossil fuels results in heavy emission of greenhouse gases, causing depletion of the ozone layer, global warming and other serious environmental threats. The rapid increase in human population demands more agricultural production, which is achievable by using heavy nitrogenous fertilizers. Agricultural crops, rice, maize and wheat, have an

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