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Schlagwörter:
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Zusammenfassung:
Activation of organ identity genes at the shoot apical meristem is largely regulated by changes in the chromatin state of the respective loci. We study the dynamics of such activation events in an inducible system for flower development (Wellmer et al., 2006), in which idle flower development can be resumed by dexametasone treatment. We generated a developmental time series starting from leaf tissue and covering the complete process of flower morphogenesis. In this series, we performed quantitative analysis of repressive (H3K27me3) and activating (H3K4me3) histone marks by ChIP-seq and transcriptome analysis. The generated dataset allows direct, genome-wide correlation of chromatin states and expression levels, with temporal resolution during gene activation processes. Interestingly, our (so far analysed) ChIP-seq data show that unanticipated chromatin changes accompany gene activation: while changes in H3K27me3 and H3K4me3 levels during flower morphogenesis affect around 4000 and 1200 genes, respectively, we observed only very subtle changes in H3K27me3 after two days of induction, although expression of floral organ identity genes is already strongly elevated. Only 14 genes were significantly changed at this time point. However, more than 100 genes seem to change in H3K4me3 levels and in a more pronounced manner than for H3K27me3. These results suggest that activation of a locus could be predominantly accompanied by deposition of activating marks, while removal of repressive marks occurs later in time. I will discuss how this first dataset, together with identification of transcriptional phases, will contribute to resolve the temporal succession of gene activation events at the chromatin.
