lire cette page en :

Deciphering genotypic variability of plant adaptation to N supply by combining a whole plant CN functioning model (ARNICA) and a root architecture model (MiniROOT) on Arabidopsis thaliana

Céline Richard-Molard
INRA, UMR Ecologie fonctionnelle et Ecotoxicologie des Agroécosystèmes, Thiverval Grignon
le 09/04/2015 à 10:30


The increase of environmental pressures and EEC control regulations lead to the development of low input cropping systems. To face this new context, breeding cultivars more efficient for N and able to sustain N limitation becomes a real issue. The identification of the key traits determining nitrogen use efficiency remains difficult because plant response to N limitation is a set of interacting processes, displaying a wide genetic and environmental variability and leading to a wide range of plant phenotypes.

To cope with this plasticity and integrate processes at the whole plant scale, our strategy was to develop a simple compartmental model of C and N absorption and partitioning during vegetative growth of A. thaliana. The ARNICA (ARabidopsis NItrogen CArbon) model is based on interactions between C and N fluxes in shoot and root compartments. It combines integrative variables and parameters defined as efficiencies of plant CN functioning and morphogenesis. This mechanistic model was designed sufficiently simple to be compatible with a medium throughput phenotyping of all of the 11 parameters.

By using the model on a core-collection of ecotypes representing 100% of allelic diversity and on Arabidopsis mutants, we were able to identify N uptake efficiency as the main parameter explaining the strong GxE variability of plant response to N supply.

As NupE results from N uptake capacities and root system size, the next step was to evaluate the involvement of root morphogenesis on plant adaptation to N supply. More precisely, our question was to evaluate to what extend the modifications of root architecture in response to N supply derived from the modification of C flux arriving from shoot. This lead to the development of MINI-ROOT, an object oriented model connected to ARNICA, which simulates root morphogenesis during vegetative growth and was designed to account for the effect of endogenous C availability on root architecture. Only 12 parameters were needed to simulate contrasted responses of root system architecture under various CxN culture conditions. Root length and branching, as well as time of emergence of lateral roots were well predicted, suggesting that most of the modifications of root system architecture in response to limiting N supply were driven by modifications of aerial C fluxes.

This work illustrated the interest of a model-assisted selection approach to screen the pertinent selection traits among the numerous one involved in a complex plant response.

This is a joint work with François Brun, Loïc Pagès and Bertrand Ney.