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Thesis started december 1^st 2016, Defended in september, 2020 8^th
Funding:  thèse en co-tutelle entre l'université d'Alger et l'ED VAS dans le cadre du projet bilatéral franco-algérien TASSILI
Direction: Anne-Marie Chèvre

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Abstract

Self-incompatibility (SI) is a widespread mechanism in flowering plants allowing them to recognize and reject self-pollen. This genetic system, controlled by a highly polymorphic S locus and various SI regulatory genes, maintains genetic diversity. In this study, we explored the impact of ancient and recent polyploidization events on the SI system and on the evolutionary dynamic of the genes involved in this mechanism in Brassica. We showed that most of the SI regulatory genes returned to a single copy after the triplication event (WGT) experienced by Brassica species. The study of a contrasted SI phenotype between two B. rapa genotypes harbouring the same S haplotype revealed that all the S locus genes (SRK, SCR, SLG) and the SI regulatory genes have an intact coding-sequence and are transcribed, suggesting (post) translational modifications or still unknown regulatory genes involved in this contrasting phenotype between these two varieties. The immediate
impact of polyploidization events on the SI phenotype analysed by resynthesizing several B. napus (oilseed rape) lines has shown that the initial allelic composition of diploid parents plays a determining role in the phenotype of synthetic oilseed rape. Over the generations, some progenies of oilseed rape SI individuals may have partial levels of self-compatibility. In these individuals, the investigation of the potential role of structural and functional variations has not shown any obvious correlation with the phenotypes observed, suggesting the potential role of (post)-traductional modifications in these phenotypic changes or that some regulatory genes of the SI system remain to be discovered in Brassica.

Keywords: Self-incompatibility, S-locus, Brassica, Polyploidy, Resynthesized rapeseed

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