Distinct signalling pathways and transcriptome response signatures differentiate ammonium- and nitrate-supplied plants

Abstract

Nitrogen is the only macronutrient that is commonly available to plants in both oxidized and reduced forms, mainly nitrate and ammonium. The physiological and molecular effects of nitrate supply have been well studied, but comparatively little is known about ammonium nutrition and its differential effects on cell function and gene expression. We have used a physiologically realistic hydroponic growth system to compare the transcriptomes and redox status of the roots of ammonium-and nitrate-supplied Arabidopsis thaliana plants. While~60% of nitrogen-regulated genes displayed common responses to both ammonium and nitrate, significant 'nitrate-specific' and 'ammoniumspecific' gene sets were identified. Pathways involved in cytokinin response and reductant generation/distribution were specifically altered by nitrate, while a complex biotic stress response and changes in nodulin gene expression were characteristic of ammonium-supplied plants. Nitrate supply was associated with a rapid decrease in H2O2 production, potentially because of an increased export of reductant from the mitochondrial matrix. The underlying basis of the nitrate-and ammonium-specific patterns of gene expression appears to be different signals elaborated from each nitrogen source, including alterations in extracellular pH that are associated with ammonium uptake, downstream metabolites in the ammonium assimilation pathway, and the presence or absence of the nitrate ion.

Hydroponic culturing upregulates sucrose and glutamine metabolism by enhancing their utilization via intermediates of aerobic pathway in wheat

“…In our experiments NH 4 Cl supply caused a significant increase in amino acids content as compared with KNO 3 and NH 4 NO 3 plants which is consistent with the results of Pasqualini et al (2001);Patterson et al (2010) who proposed that NH 4 + ion diverted the assimilated carbon mainly towards amino acids. As KNO 3 and NH 4 NO 3 nitrogen source resulted in higher nitrogen content, which can be correlated with higher activities of nitrogen metabolizing as well as aminotransferases enzymes as also reported by Below et al (2000).…”

The Kinase CIPK23 Inhibits Ammonium Transport in Arabidopsis thaliana

“…In the yeasts Saccharomyces cerevisiae and Candida albicans, the kinase NPR1 regulates ammonium transport (Boeckstaens et al, 2007;Neuhäuser et al, 2011), but the kinase that regulates plant AMT1s is currently unclear. Plant kinases related to S. cerevisiae NPR1 are members of the CIPK family, and some CIPK genes in plants are upregulated during the ammonium response (Canales et al, 2014;Patterson et al, 2010;Engelsberger and Schulze, 2012). However, whether CIPKs are involved in ammonium transport in plants is currently unclear.…”

NH4+-mediated Protein Phosphorylation in Rice Roots

“…In Arabidopsis, a series of transcriptome analyses have demonstrated that N nutrient regulated expressions of global genes involved in diverse aspects including metabolic and developmental processes (Gutierrez et al, 2008;Patterson et al, 2010;Scheible et al, 2004;Wang et al, 2000). In rice, AMT1;1 and AMT1;2 are up-regulated in response to NH 4 + , whereas AMT1;3 is up-regulated by nitrogen deprivation (Kumar et al, 2003;Sonoda et al, 2003).…”