Signal molecules controlling nitrate uptake by roots

The efficiency of nitrate uptake is a key point to decrease the waste of fertilizer and protect the environment. There are some signal substances participating in the nitrate control system. This paper reviewed the signals, including positive feed-forward and negative feedback signals, controlling nitrate uptake by roots. Firstly, sugar signals are related to photosynthesis and constitute a positive feed-forward signal. Sucrose had been identified as the positive feed-forward signal, and its nature was elucidated. Secondly, reduced N signals are related more generally to growth and constitute negative feedback. It is difficult to pinpoint an amino acid controlling nitrate uptake since they can convert each other. Thirdly, the interaction of two kinds of signal was analyzed. Finally, the current studies of a regulatory network of the signal molecules that control nitrate uptake and nitrate transporters in rice were reviewed. It was beneficial to understand N metabolism control.