Rhodes, XVI International Congress on Molecular Plant-Microbe Interactions

Plant adaptations include the capacity to respond to changes of the nutrient availability in the soil by modulating their root system developmental plan. NO3- is able to trigger signaling pathways modulating systemically, or locally, lateral root development. In legumes nitrate availability is known to strongly affect nodule initiation, development and functioning as low and high concentrations exert a positive and negative effect on these, respectively. Plant transporters have been involved in the signalling pathways for scanning the substrates concentration in the rooted area. We are currently investigating the possible involvement of NPF and NRT2 genes in the control of nodulation. In silico search allowed the identification of the L. japonicus NPF and NRT2 families of about 70 and 4 members, respectively. The NPF members have been classified into the 8 sub-clades recently identified among the plant NPF proteins. We are especially focusing our attention on 4 transporters (1 NPF and 3 NRT2) likely involved in the uptake of external nitrate and a group of seven NPF proteins whose expression is induced in the nodular tissue. An atlas of the spatial profile of promoter activity as well as a biochemical characterization conducted in injected Xenopus leavis oocytes to identify the substrate specificity and transport mechanisms, will be presented. Furthermore, a reverse genetic approach has been conducted on Lotus LORE1 lines tagged in these transporters genes. The phenotypical analysis, is revealing novel information abo