Nitrate Transport and Signaling

As sessile organisms, plants have developed a sophisticated network of mechanisms to adapt and optimize their growth to the constantly and rapidly changing nutritional environmental conditions. The transport of nitrate in higher plants is a paradigm of this regulatory control as either external or internal cues can govern the root uptake ability depending on the nutrient demand and nitrogen availability in the soil. Plant adaptations also include the potential to respond to changes of nitrate concentration in the soil by modulating the root system developmental plan. It is known that in leguminous plants, nitrate availability in the soil can also strongly affect nodule formation as low and high concentrations exert a positive and negative effect on initiation of the organogenesis process, respectively. Nitrate can act both as a nutrient and a signal for the induction of plant root responses, and members of the nitrate and peptide transporters family (NPF and NRT2) play crucial roles in the control of such signaling pathways. This chapter presents an overview of the genomic and transcriptomic data reported for the Lotus japonicus NPF and NRT2 family members, and their possible roles in the control of the nodulation program are discussed.