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Dernière mise à jour : Mai 2018

Menu Logo Principal Agrocampus Ouest Angers University   IRHS

IRHS

Nitrate perception & Signalling

While many studies on legume biology are focusing on symbiotic nitrogen fixation processes, our team aims to characterize the early post-germinative processes leading to successful legume establishment taking into account the impact of exogenous nitrate or biotic/abiotic stresses.
  • Nitrate transport, Signalling and Root architecture

Root growth is crucial for successful seedling establishment. It depends on nutrient availability and notably on the level of nitrate content in the soil which varies greatly. However, nitrate is not only a nutrient but also a signal involved in the regulation of primary root growth. At early stage, we showed in Medicago truncatula, a model legume, that nitrate can inhibit primary root growth.

The goal of the IoNIS project (funded by RFI Objectif Vegetal 2017-2020) is to decipher the nitrate signaling pathway that leads to a reduction of primary root growth in M. truncatula by the restriction of cell elongation. We have recently found that the nitrate transporter MtNPF6.8 acts as a nitrate sensor involved in the response to nitrate. How the signal, perceived by the transporter, is transduced is still not known. However, the fact that abscisic acid (ABA) restored the inhibitory effect of nitrate in npf6.8 mutants suggests that ABA is involved in the signal transduction. Because reactive oxygen species govern root growth through cell division and elongation, we want to determine whether nitrate modifies the ROS balance. We also want to identify the genes mediating the nitrate signal. We will mainly use two genotypes contrasting for nitrate sensitivity, a wild type genotype sensitive to nitrate (R108) and the npf6.8 mutant in the same genetic background. The impact of nitrate on ABA or ROS accumulation in different parts of the root will be assessed. In parallel, the impact of exogenous nitrate on gene expression in the wild type and in the npf6.8 mutant lines will be determined by both transcriptomic and proteomic studies. We will work in synergy with experts in transcriptomics and bioinformatics (present locally) and proteomics (Paris Saclay).

 

  • Nitrate & Biotic stress

Early stages of plant development are highly susceptible to environmental variations. Plants have to develop sophisticated defence responses to cope with biotic stress, but nitrogen availability influences the plant resistance to pathogens. The mechanisms leading to the nutrient-induced changes in disease development are complex and multifarious. In higher plants, nitrate uptake through the roots is mainly achieved by proteins of two families, NPF (Nitrate Transporter1 (NRT1)/Peptide transporter (PTR) family) and NRT2 (nitrate transporter2). Any functional role for a NPF transporter in the features of plant-pathogen interactions has been reported until now during seedling establishement and at the rosette stage. Thus, we are interested to investigate whether AtNPF6.3 (AtNRT1.1; CHL1), a nitrate sensor with a dual transport/signalling function, would be involved in the response of A. thaliana to the necrotrophic fungus Alternaria brassicicola.

In order to functionally characterize the involvement of AtNPF6.3 in plant resistance to A.brassicicola by deciphering the role of nitrogen in plant fungal pathogen intreactions, the NPFun project (funded by RFI Objectif Vegetal 2015-2018) aims two main objectives: (i) to determine nitrate and AtNPF6.3 involvement in the relationship between plant nitrogen metabolic status and the sensitivity to fungal infection and (ii) to investigate the AtNPF6.3-dependent signalling pathways in response to fungal attack.

See also

Seedling Vigour Lire >>>

Mitochondrial Biology Lire >>>