Nitrogen signal systems in bacteria, fungi and plants

Due to its essential role in life process, nitrogen (N) uptake and metabolism is precisely regulated in all kinds of life organisms. The regulation of N uptake and metabolism depends on the sensing of internal and external N signals. In the past decades, much knowledge has been acquired in this aspect in bacteria and fungi. In plants, however, the progress is relatively slow and the knowledge about N signals is scare. In this review, the major component in N signal systems in bacteria, fungi and plants were compared so as to provide new insight for N signal research in pant systems.