Construction of regulatory gene networks exploiting natural variability in Arabidopsis thaliana

EcoNet program aims at identifying regulatory modules in gene networks that have evolved in Arabidopsis thaliana natural ecotypes in order to adapt NO3—‐ nutrition to fluctuating environment. The use of natural variation is now extensively used to decipher gene functions through Genome Wide Association Mapping (GWAM) (for details see : (Weigel, 2012)). Here we decided to probe a subset of the Norborg ecotype collection (a core collection of Arabidopsis ecotype fully sequenced: (Atwell et al., 2010)) for NO3—‐ heterogeneity response ((Ruffel et al., 2011)). The Pr Coruzzi has been personally involved in the experiments described below and beneficiated from Sandrine Ruffel and Gabriel Krouk expertise on the experimental set—‐up and 15N measurement. An experimental set—‐up has been used as described in Ruffel et al 2010. In brief plants are grown in vertical Petri dishes. After 10 days the primary root is cut in order to let 2 lateral root grow. Then, these lateral roots are treated with different N sources. This help to reveal after 5 days how roots adapt to heterogeneous conditions of the soil. The expected response is that root in contact with NO3—‐ rich zone are able to preferentially grow in order to compensate for the N deprivation perceived by the –N root (Figure 1). Here the NO3—‐ provided to plants was labeled with 15N. The 2 parts of the root system, and the plant shoots have been analyzed by mass spectrometry thanks to Pascal Tillard (IR INRA). This set—‐up was built to decipher if 15N allocation can differs across ecotypes. Interestingly, since all the accessions used in this work have been fully sequenced we expect to identify genes being strongly associated with N allocation variation, and root development response upon NO3—‐treatment.