The final aim of our studies is to generate new plant genotypes, showing a better nitrogen use efficiency that allows constant yield (biomass production and seed quality) even under low nitrogen supply. We focused our research on three aspects:

Transport of nitrate/nitrite within the whole plant

Nitrate is both the major source of nitrogen, at least for our temperate culture conditions, and the first stored nitrogen compound used to sustain growth under external constraints. We study the molecular mechanisms that govern soil nitrate uptake by plant roots and its transport, storage and mobilisation within the whole plant during development. We particularly focus our studies on the high affinity nitrate transport system, which involves the NRT2 protein family. The translocation of the first product of its assimilation, nitrite, into the chloroplast is still not completely elucidated in higher plants and one of our target genes, encoding the chloroplastic PII protein (see below), seems to be involved in this step

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Hydroponics

Signaling of nitrogen starvation

The plant response to nitrogen availability requires mechanisms of sensing and regulation that control and coordinate the transport and the assimilation of nitrogen at both cellular and whole plant level. Two candidate genes are studied using functional genomic approaches. The PII signal transducing protein is a highly conserved protein involved in the amino acid/sugar-starch ratio (C/N) in response to nitrogen deprivation in plants. The AtNLP genes contain a putative RWPRK DNA-binding domain. This domain is found in proteins which have been proposed to act as transcription factors and to be involved in nitrogen-controlled developmental processes. We propose that NLP7 is involved in the regulation of N perception.

Exploring natural variation for plant adaptation to nitrogen availability (more details)

Plants present a fantastic plasticity of their development in response to different environmental constraints. By using our favourite model plant, Arabidopsis thaliana, we investigate the genetic components of the adaptation of plants to nitrogen limited supply. Among several accessions, Arabidopsis plants present different patterns of development and N utilization. We would like to characterize these responses under nitrogen limited supply. For this achievement, we first measure growth rate and N metabolism of Arabidopsis plants under different nitrogen supplies. Then we identify loci associated to response variation by QTL analysis. Our work leads to the identification of genes involved in growth and nitrogen metabolism and offers bases for selection of plants which will have a better N use efficiency.