Breeding for Higher Yields of Wheat and Rice through Modifying Nitrogen Metabolism

Abstract

Wheat and rice produce nutritious grains that provide 32% of the protein in the human diet globally. Here, we examine how genetic modifications to improve assimilation of the inorganic nitrogen forms ammonium and nitrate into protein influence grain yield of these crops. Successful breeding for modified nitrogen metabolism has focused on genes that coordinate nitrogen and carbon metabolism, including those that regulate tillering, heading date, and ammonium assimilation. Gaps in our current understanding include (1) species differences among candidate genes in nitrogen metabolism pathways, (2) the extent to which relative abundance of these nitrogen forms across natural soil environments shape crop responses, and (3) natural variation and genetic architecture of nitrogen-mediated yield improvement. Despite extensive research on the genetics of nitrogen metabolism since the rise of synthetic fertilizers, only a few projects targeting nitrogen pathways have resulted in development of cultivars with higher yields. To continue improving grain yield and quality, breeding strategies need to focus concurrently on both carbon and nitrogen assimilation and consider manipulating genes with smaller effects or that underlie regulatory networks as well as genes directly associated with nitrogen metabolism.

Genetic adaptation to ammonium sustains wheat grain quality and alleviates acclimation to CO2enrichment

“…The influence of nitrogen forms on crop development, particularly flowering time, remains unresolved (Kasemsap & Bloom, 2022). Typically, CO 2 enrichment accelerates development and senescence through rubisco and photosynthesis acclimation (Sicher & Bunce, 1997).…”

“…Rarely do studies account for different inorganic nitrogen forms (Kasemsap & Bloom, 2022). Only a handful of studies have contrasted the physiological responses of wheat to NH 4 + versus NO 3 − and CO 2 levels (Bloom et al, 2002; Carlisle et al, 2012; Rubio-Asensio & Bloom, 2016), and none of the studies selected the plant materials based primarily on the degree of preference for a nitrogen form or NH 4 + tolerance.…”

“…Only a handful of studies have contrasted the physiological responses of wheat to NH 4 + versus NO 3 − and CO 2 levels (Bloom et al, 2002; Carlisle et al, 2012; Rubio-Asensio & Bloom, 2016), and none of the studies selected the plant materials based primarily on the degree of preference for a nitrogen form or NH 4 + tolerance. The limited genetic diversity in any given study (Kasemsap & Bloom, 2022) and the difficulties in precisely controlling the nitrogen forms in the root zone (Bloom et al, 2012) may underlie the lack of understanding about this topic.…”

Genome-Wide Association Study on Seedling Phenotypic Traits of Wheat under Different Nitrogen Conditions

“…NUE in wheat is affected by many factors, including genes, regulatory networks, signal transduction, and metabolic pathways [23][24][25]. Meanwhile, the response of wheat to the N environment phenotype depends on stress time, intensity, and genotype differences between species [22,26].…”

Multi-Omics Analysis Reveals Synergistic Enhancement of Nitrogen Assimilation Efficiency via Coordinated Regulation of Nitrogen and Carbon Metabolism by Co-Application of Brassinolide and Pyraclostrobin in Arabidopsis thaliana

“…In this way, it will be beneficial to increase plant productivity without adding production costs and environmental burdens from overusing N fertilizers [8]. Currently, genetic engineering approaches to overexpress genes involved in the N assimilation process have been developed to improve NUE and plant yields [9][10][11]. Overexpression of nitrate reductase (OsNR2) or nitrite reductase (OsNiR1) improved NUE and grain production in rice [12,13].…”