TANDEM ZINC-FINGER/PLUS3 integrates light signaling and flowering regulatory pathways at the chromatin level.

Environmental and endogenous stimuli determine plant developmental transitions including flowering through multiple signaling cascades. Although the key activators and repressors of flowering initiation are defined, the components and mechanisms integrating light signaling and flowering pathways are not fully established. This study investigates the role of TANDEM ZINC-FINGER/PLUS3 (TZP), a light-integrating transcriptional regulator, to elucidate how light cues influence the epigenetic regulation of flowering in Arabidopsis thaliana. To dissect the molecular function of TZP, this study employed a combination of genetics, RNA sequencing, chromatin immunoprecipitation sequencing and phenotypic assays. These approaches were used to determine TZP's genomic binding sites, its downstream gene targets and its influence on flowering time and chromatin modifications. TANDEM ZINC-FINGER/PLUS3 was found to directly associate with the promoter regions of chromatin-modifying genes, including FLOWERING LOCUS D (a histone H3K4 demethylase) and histone deacetylase 6 (a histone deacetylase). This regulation promotes a chromatin environment that represses FLOWERING LOCUS C (FLC) transcription, thereby accelerating flowering. TANDEM ZINC-FINGER/PLUS3 thus functions upstream of multiple pathways integrating photoperiodic and autonomous floral cues. TANDEM ZINC-FINGER/PLUS3 mediates crosstalk between light signaling and flowering pathways by modulating chromatin structure at the FLC locus. This provides a mechanistic framework for understanding how environmental signals dynamically influence epigenetic regulation of developmental transitions.