Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)
Jeudi 18 mars 2010
Amphi 208 (Cœur d’Ecole) à 14h
Adaptation of Arabidopsis thaliana to Nitrogen availability
Institut Jean-Pierre Bourgin (IJPB), INRA Versailles
N is an essential macroelement for plant growth. To cope with large variations in nitrate concentrations in soils, two uptake systems coexist within plants, a low-affinity nitrate transport system (LATS) and a high affinity transport system (HATS). Nitrate transporters are encoded by the NRT1 and NRT2 gene families. In Arabidopsis, the NRT2 family contains 7 genes, which are differentially regulated at the level of organ specificity or in response to environmental conditions. NRT2.1 acts as the main component of high affinity nitrate uptake through root plasma membranes. More recently, we showed that the NRT2.7 gene is predominantly expressed during seed maturation and controls seed nitrate content. Work is in progress to elucidate the role of other members of the family, NRT2.4, NRT2.5 and NRT2.6. Nitrate, beside its role as nutrient, acts as a signal molecule for triggering many adaptative responses to changes in N availability. How such nitrate specific mechanisms are regulated at the molecular level is poorly understood. Our approach, aiming on the description of new regulatory Arabidopsis proteins, exploits knowledge from other species. Legume-specific symbiotic nitrogen fixation is under the control of the putative transcription factor, NIN, A homologous gene family NLP (NIN Like Protein) was found in the Arabidopsis genome. nlp7 knockout mutants constitutively display several traits of nitrogen starved plants. Nitrate resupply experiments show an altered response of several nitrate inducible genes for the nlp7 mutants. NLP7 expression pattern is consistent with a function in the sensing of N and translational fusions with the green fluorescent protein (GFP) show a nuclear localization for NLP7. Altogether, we propose NLP7 as an important element of the nitrate signal transduction pathway. However, the NLP gene family contains 9 members, including NLP6 which is very closely related to NLP7. Double mutants nlp7nlp6 give new insights in the role of NLP proteins for the regulation of N related traits.
Contact : Marc Lepetit