Polycomb group (PcG) proteins are essential to maintain gene expression patterns 
during development. Transcriptional repression by PcG proteins involves 
trimethylation of H3K27 (H3K27me3) by Polycomb Repressive Complex 2 (PRC2) in 
animals and plants. PRC1 binds to H3K27me3 and is required for transcriptional 
repression in animals, but in plants PRC1-like activities have remained elusive. 
One candidate protein that could be involved in PRC1-like functions in plants is 
LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), because LHP1 associates with genes marked 
by H3K27me3 in vivo and has a chromodomain that binds H3K27me3 in vitro. Here, 
we show that disruption of the chromodomain of Arabidopsis thaliana LHP1 
abolishes H3K27me3 recognition, releases gene silencing and causes similar 
phenotypic alterations as transcriptional lhp1 null mutants. Therefore, binding 
to H3K27me3 is essential for LHP1 protein function.