Polycomb group (PcG) proteins are key epigenetic regulators of development.
The highly conserved Polycomb repressive complex 2 (PRC2) represses thousands
of target genes by trimethylating H3K27 (H3K27me3). Plant specific PcG
components and functions are largely unknown, however, we previously
identified the plant-specific protein BLISTER (BLI) as a PRC2 interactor. BLI
regulates PcG target genes and promotes cold stress resistance. To further
understand the function of BLI, we analyzed the transcriptional profile of
bli-1 mutants. Approximately 40% of the up-regulated genes in bli are PcG
target genes, however, bli-1 mutants did not show changes in H3K27me3 levels
at all tested genes, indicating that BLI regulates PcG target genes downstream
of or in parallel to PRC2. Interestingly, a significant number of BLI
regulated H3K27me3 target genes is regulated by the stress hormone absciscic
acid (ABA). We further reveal an overrepresentation of genes responding to
abiotic stresses such as drought, high salinity, or heat stress among the up-
regulated genes in bli mutants. Consistently, bli mutants showed reduced
desiccation stress tolerance. We conclude that the PRC2 associated protein BLI
is a key regulator of stress-responsive genes in Arabidopsis: it represses
ABA-responsive PcG target genes, likely downstream of PRC2, and promotes
resistance to several stresses such as cold and drought