Abstract
Inorganic nitrogen sources play an important role for regulating plant growth and development. To bring molecular approaches to study for nitrogen assimilation and the signal transduction, we identified a series of nitrogen assimilatory genes in maize and characterized the regulatory mechanism. Consequently, we revealed that there is a wide regulatory network of nitrate-specific responsive genes, and that plastidic glutamine synthetase (GS) is differentially regulated in response to light and nitrate between bundle sheath cells and mesophyll cells in maize, a C4 plant. We also characterized molecular mechanism of ammonium-response of cytosolic GS in maize roots. On the other hand, recent our research strongly suggests that in addition to nitrate ions, cytokinin would be another root-to-shoot signal substance communicating nitrogen-availability. I will introduce an overview of the nitrogen signaling system in higher plants and discuss physiological differentiation of the two pathways.
