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During the past years, we were able to estimate the distribution of crossing-over events (CO) in chromosome 3B and initiate study of 4 genes from the rad51 family implicated in this process. We pursue this work in two directions:

• Distribution of COs and impact of intrinsic sequence properties

The purpose is to better understand the molecular basis for the recombination gradient in wheat. The sequence of chromosome 3B will allow us to study the distribution of CO events at a level not yet achieved so far in bread wheat through the development of a large number of markers (SSRs, ISBPs and SNPs) distributed regularly along the chromosome and thus covering both the telomeric and centromeric parts as well as the euchromatic and heterochromatic regions. Thus, we identify and compare with greater precision those regions that display divergent recombination rates (hot/cold spots) and study correlations with particular features of the sequence, such as the presence of genes or transposable elements, the GC content or other specific motifs. We would like to focus more particularly on the epigenetic landmarks that confer particular structures to the DNA (condensation, histone methylation) and on the relationships that may exist with gene expression.

• Characterisation of genes invloved in recombination

We have undertaken an in-depth analysis of the structure, function, expression, evolution and diversity of genes known to be involved in recombination in order to understand their role in the regulation of recombination. The long-term objective is to be able to modify the recombination rate in wheat, particularly in centromeric regions, to increase genetic recombination capacities and gain access to a diversity that is currently underexploited. In the context of an innovative project (POLYMERE) funded by INRA department GAP (Genetique et Amélioration des Plantes) and an ANR project (DUPLIC), funded in 2010, we start studying the expression and evolution of genes that are known to be involved in the formation of COs in the model species A. thaliana. We focus particularly on evaluating the loss or retention profiles of homoeologous copies during polyploidisation in different contexts of polyploidy (2x, 4x, 6x, natural or synthetic) in wheat, and compare them with those obtained on another recent, cultivated polyploid, rapeseed (collaboration with E. Jenczewski, INRA Versailles). One of the objectives is to estimate the evolution of these genes in terms of the presence or absence (loss of copy) of expression (difference between homoeologs, silencing) and function (study of mutants, complementation). We want also to study the natural diversity (collaboration with F. Balfourier) or induced diversity (irradiation or transgenic mutants, collaboration with the GDEC validation platform) of these genes in collections.