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Réponse du méthylome suite à l'exposition au froid chez une espèce à génome complexe : le maïs (Zea mays ssp. mays)

Abstract : Molecular characterization of plant response to environnemental constraints allows to both better understand plant adaptation and help crop improvement. The epigenome is composed of chromatin marks and participates to the regulation of genome expression, notably through development. It is also involved in genome stability, essentially by preventing the transposition of transposable elements (TE). The epigenome can be modified by environmental cues and better understanding this variation could give new insights on the interaction between the plant and its environnement. However, the extent of this modification, targeted sequences and underlying mecanisms remain to be elucidated. In this context, I analyzed the impact of cold on the methylome of maize, a plant with a complex genome with high proportion of TEs. In a first part, I analyzed the methylome of a cold-sensitive genotype, B73, using whole genome bisulfite sequecing (BS-seq). This comparative analysis between “stressed” and “unstressed” plants was carried out (i) at the chromosome scale, without a priori definition of a DNA methylation difference and (ii) at a localized scale (Differentially Methylated regions, « DMRs ») using high minimum methylation difference rate (10%). These two types of analysis revealed that cold triggers hypermethylation at the genome scale, as well as. hyper-and-hypo-methylation at the local scale. These variations were observed in the 3 contexts of cytosine and occur in different genomic regions associated with genes and TEs. This suggests the parallel activation of different regulatory pathways in response to cold. In a second part, I focused on following-up methylation changes through development and in the progeny in conjunction with the genomic sequences and the cytosine context involved. In a third part, I studied the relationship between methylome variations and cold sensitivity by comparing the methylomes of three maize genotypes (B73, F2 and F331) with a contrasted phenotypic response to cold.
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Zeineb Achour. Réponse du méthylome suite à l'exposition au froid chez une espèce à génome complexe : le maïs (Zea mays ssp. mays). Génomique, Transcriptomique et Protéomique [q-bio.GN]. Université Paris Saclay (COmUE), 2018. Français. ⟨NNT : 2018SACLS102⟩. ⟨tel-02130625⟩

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