Imitation Switch chromatin remodeling factors and their interacting RINGLET proteins act together in controlling the plant vegetative phase in Arabidopsis

During their life cycle, flowering plants must experience a transition from vegetative to reproductive growth. Here, we report that double mutations in the Arabidopsis thaliana IMITATION SWITCH (AtISWI) genes, CHROMATIN REMODELING11 (CHR11) and CHR17, and the plant-specific DDT-domain containing genes, RINGLET1 (RLT1) and RLT2, resulted in plants with similar developmental defects, including the dramatically accelerated vegetative-to-reproductive transition. We demonstrated that AtISWI physically interacts with RLTs in preventing plants from activating the vegetative-to-reproductive transition early by regulating several key genes that contribute to flower timing. In particular, AtISWI and RLTs repress FT, SEP1, SEP3, FUL, and SOC1, but promote FLC in the leaf. Furthermore, AtISWI and RLTs may directly repress FT and SEP3 through associating with the FT and SEP3 loci. Our study reveals that AtISWI and RLTs represent a previously unrecognized genetic pathway that is required for the maintenance of the plant vegetative phase.