Nitrogen and Signaling

Abstract

SummaryIn addition to their role as nutrients, nitrogen (N)-containing compounds are considered to be signaling molecules in plants. Plant development is modified by N-metabolites. Root architecture and root-to-shoot allocation are particularly sensitive to soil nitrate and these processes respond to nitrate via several mechanisms. Metabolic pathways are also influenced by N-compounds at several levels. The molecular mechanisms that exert this control are not yet understood but recent evidence suggests that N-effectors act by regulating gene expression as well as by exerting post-transcriptional and post-translational effects. Like the processes of nitrate and ammonium uptake and assimilation, organic acid synthesis and starch biosynthesis are modified by nitrate, glutamine and other products of N assimilation. In this chapter, we discuss the evidence for the role of nitrate and nitrogen metabolites, such as glutamine, as signals regulating plant morphology and metabolism.