Application of genomics to dissect Polycomb-group protein mediated control of plant development (PcG-code)
Zusammenfassung der Projektergebnisse
PcG-code aimed to discover novel genes and gene networks with important roles in plant development. A particular focus was the role of Polycomb Group (Pc-G) proteins in the regulation of developmental gene expression. We used a reverse genomic approach, which combined whole-genome chromatin profiling and expression studies to define candidate gene sets that were tested for their impact on Arabidopsis development. We discovered novel genes that control leaf and apical meristem development. In particular, DPA4 was shown to repress CUC genes which are key factors involved in organ boundary formation and meristem maintenance. CUC genes are regulated by micro RNAs but the regulation of CUC genes by DPA4 was shown to be independent. Although a very significant candidate list was selected based on genomic parameters for a potential role in seeds, so far the genetic analysis did not reveal novel key regulatory genes. One possible conclusion from is that although strictly correlated with seed-specifically expressed genes, the role of Pc-G proteins in seeds is not predominantly developmental. A potential mechanism by which Pc-G proteins impact root development was revealed by demonstrating that the key regulator RBR complex shares subunits with Pc-G complexes. Furthermore, results from Pc-G showed that the Pc-G associated chromatin modification, histone H3 tri-methyl lysine 27 (H3K27me3) is dynamically distributed between leaf tissue and the apical meristem. In this comparison, differential H3K27me3 correlated with differences in gene expression for H3K27me3 target genes. In contrast, if compared within the same tissues (young seedlings) for different Arabidopsis accessions, the differences in the H3K27me3 are negligible compared to differences in gene expression. Alterations in H3K27me3 were not mainly correlated with differences in expression but with polymorphic transposons in the vicinity of differentially targeted regions.
