Redox metabolism: the hidden player in C and N signaling?

While decades of research have considered redox metabolism as purely defensive, recent results show that ROS are necessary for growth and development. Strikingly, close relationships were found between the regulation of nitrogen (N) metabolism and ROS in response to both carbon (C) and N availability. Root NO3- uptake and N metabolism have been shown to be regulated by a signal coming from the Oxidative Pentose Pathway in response to C signaling. As a major source of NADP(H), OPPP is critical to maintain redox balance under stress situations. Furthermore, recent results suggest that at least part of the regulation of root NO3- transporter by N signaling is also linked to the redox status of the plant. This leads to the question of a more general role of redox metabolism in the regulation of N metabolism by C and N. This review will (i) highlight the role of OPPP in C signaling and redox metabolism and (ii) the interaction between redox and N metabolism. We will then discuss how redox metabolism could be an important player in the regulation of N metabolism in response to C/N interaction and the implication for plants' adaptation to extreme environment and the development of future crops.