Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)
Jeudi 4 octobre 2012
Amphi 206 (Cœur d’Ecole) à 13h
Evolution of self-incompatibility in Arabidopsis: dominance/recessivity at the gene controlling pollen specificity is controlled by a network of small regulatory RNAs
Laboratoire de génétique et évolution des populations végétales, UMR CNRS 8198 , Université Lille 1
Dominance, the genetic phenomenon whereby one of the two alleles at a diploid locus is masked at the phenotypic level, is one of the earliest observations of classical genetics, yet also one whose genetic basis and evolution remain poorly understood. A recent landmark paper identified, embedded within the gene cluster controlling self-incompatibility in the Brassicaceae, a novel small non-coding RNA acting in trans- as dominance modifier of the gene controlling pollen specificity via de novo methylation of the promotor of the recessive allele. This discovery provides an elegant mechanistic model for dominance/recessivity interaction in pollen between two alleles, and hence first description of a dominance modifier. However, a major limitation of the proposed model is that the self-incompatibility locus in most plant species is typically highly multiallelic with dozens of allelic classes and a complex network of dominance/recessivity among the alleles. This observation raises the intriguing question of how such a simple mechanistic model can account for the complexity of the dominance/recessivity relationships. We used a combination of genomic approaches to adress this issue Arabidopsis halleri, a species with a large number of highly divergent S-alleles. Our results demonstrate a crucial role for co-evolutionary processes between the repertoire of small-RNA producing loci and their target sites.
Contact : Françoise Gosti