REF6 recognizes a specific DNA sequence to demethylate H3K27me3 and regulate organ boundary formation in Arabidopsis.

Xiaofeng Cao and colleagues report that the H3K27 demethylase REF6 binds directly to a specific DNA sequence through its Cys2His2 zinc-finger domains. They show that Arabidopsis thaliana mutants for REF6 exhibit defects in cotyledon separation, thereby linking sequence-specific H3K27me3 demethylation to organ boundary formation.