Nitrate, a nutrient signal controlling nodule nitrogen fixation activity in l. japonicus and how the nitrate transporters are involved

Vladimir Totev Valkov 
IBBR - UOS Napoli - Italy

April 14, 2021 (11:30-12:30)
Webinar Link: https://global.gotomeeting.com/install/902261053

Abstract: Nitrate is an essential source of nitrogen (n) for plant growth; it is a primary inorganic nutrient for the nitrogen assimilation pathways and at the same time is an important signal for plant development. Low-(nrt1/npf) and high- (nrt2) affinity transport systems are involved in the nitrate uptake from the soil and its distribution throughout different plant tissues. Nitrate plays also a key role during symbiotic nitrogen fixation (snf). This is a unique process in which legume plants establish symbiotic interactions with soil bacteria, rhizobium, and form new organs, nodules, where differentiated bacteroids reduce atmospheric dinitrogen (N2) to ammonia (NH3), which is used as a nitrogen source by the host plant. legume plants have evolved complex signalling networks to respond to both external and internal levels of nitrate in order to optimize snf in nodules. This involves long-distance, systemic and local responses. The question we have addressed in our recent articles is how nitrate may control the nodule functioning leading to an efficient N2-fixation. In the legume-rhizobia symbiotic interaction, the responsiveness to nitrate has been mainly associated to inhibitory pathways affecting different steps of nodulation such as formation, development and functioning. In the case of nodule activity, high concentrations of external nitrate trigger a dramatic decrease of nitrogenase, the key bacterial enzyme required for N2-fixation. However, we have contributed to highlight a new, positive action played by low, permissive concentrations of nitrate in order to maintain the energy status required for efficient N2-fixation in mature nodules. In particular, the functional characterizations of npf and nrt2 transporters revealed their action on nitrate allocation and distribution through the nodule tissue

Author's Info: https://ibbr.cnr.it/ibbr/info/people/vladimir-totev-valkov