Polycomb Group Proteins (PcGs) is critical in defining the epigenetic blueprint for animal and plant development. In plants, loss of different PcGs display both common and unique phenotypic defects, yet little is known about how these are established. Here, based on quantitative comparison of epigenomics data from mutants of key PcG components in Arabidopsis seedlings, we found that the PcG partners of CURLY LEAF (CLF), one of the major plant H3K27 trimethyltransferases, determines its selectivity in repressing gene loci involved in distinct developmental programs. The non-redundant role of CLF in determining flower development is specifically associated with HETEROCHROMATIN PROTEIN1 (LHP1). This context dependent effect of CLF corresponds well with tissue-biased target gene expression, and importantly, to differential co-occupancy of transcription factors, such as MADS box and B3-domain transcription factors. These results provide valuable insight as to the dynamic interplay between different PcGs and their collaborative control of plant development.
Overall design: To compare the effect of different PcGs on epigenetic structure from the genome-wide scale, we used chromatin immunoprecipitation followed by high-throughtput sequencing (ChIP-seq) to characterize the genome-wide binding profile of H3K27me3 in Col, clf-29, tfl2-2, atbmi1a/b and atring1a/b; To investigate the functional consequence of the distinct H3K27me3 profile controlled by different combinations of PcGs, we characterized the transcriptome change in PcG mutants, including Col, clf-29, tfl2-2, lhp1-6, atbmi1a/b, atring1a/b, and clf29swn21.
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