Doctorate thesis of National Institute of Further Education in Agricultural Science
Friday, December 19, 2014
NPF involvement in nitrate transport and sensing in Arabidopsis thaliana
Sophie Léran
BPMP, “Integration of Nutritional Functions” team
Jury :
Mme Marie BOUDSOCQ, CR, INRA Evry, Examinateur
M. Jean-Philippe GALAUD, MC, UPS Toulouse, Rapporteur
M. Frédéric GAYMARD, DR, INRA Montpellier, Examinateur
M. Benoît LACOMBE, CR, CNRS Montpellier, Directeur de thèse
Mme Nathalie LEONHARDT, DR, CEA Cadarache, Examinateur
M. Sébastien THOMINE, DR, CNRS Gif-sur-Yvette, Rapporteur
M. Jean-Claude YVIN, Directeur R&D, Roullier, Dinard, Invité
Abstract :
Nitrate is a nutrient but also a signaling molecule perceived by plants. In Arabidopsis, 5 families encompass nitrate transporters: NPF, NRT2, SLAC/SLAH, ClC and ALMT. I focused my work on the NPF family (NRT1/PTR Family), comprising 53 members in Arabidopsis. Various substrates are transported by the different members: nitrate, nitrite, amino-acids, dipeptides, glucosinolates, auxin, ABA and gibberellins. During my PhD, a functional screen in xenopus oocytes led to identify two nitrate transporters: AtNPF5.5 and AtNPF5.10. In planta, AtNPF5.5 is involved in nitrogen accumulation in the embryo. Thereafter, I focused my work on the first nitrate transporter identified in plants, NPF6.3/NRT1.1/CHL1. First, its role in root-to-shoot nitrate translocation was demonstrated. Second, the functional characterization of a NPF6.3/NRT1.1 mutant carrying a punctual mutation (P492L), allowed proposing a role of the internal nitrate concentration on NPF6.3/NRT1.1 activity. Finally, a protein regulatory network involving NPF6.3/NRT1.1, two calcium sensors, CBL1 and CBL9, the kinase CIPK23 and the phosphatase ABI2 has been identified. The ABI2 contribution in nitrate transport and sensing suggests a crosstalk between nitrate and ABA signaling pathways. This work provides tools to study Arabidopsis NPF proteins and gives insights into our understanding of nitrate transport and sensing mechanisms.