PgFLC / PgFT Regulation by the PgDOF3.4‐PgULT1‐PgLHP1 Module Mediates the Low Temperature to Promote Flowering in Physalis grisea

Flowering is essential for plants to reach the survival of species and flowering is influenced by many environmental factors. However, trithorax group (TrxG) mediated epigenetic modification mechanisms of Physalis grisea under low temperature on flowering remain largely unknown. Here, we report that TrxG core member ULTRAPETALA1 (PgULT1) inhibits flowering in P. grisea by interacting with Polycomb Group (PcG) member LIKE-HETEROCHROMATIN-PROTEIN 1 (PgLHP1) and transcription factor DNA-BINDING-ONE-FINGER 3.4 (PgDOF3.4) to regulate H3K4me3 and H3K27me3. PgULT1 overexpression delayed flowering, yet flowering was relatively promoted under low temperatures. Similarly, PgDOF3.4 confers delayed flowering by transcribing PgULT1, PgLHP1, and FLOWERING LOCUS C (PgFLC). Protein interaction assays indicated that PgULT1, PgDOF3.4 and PgLHP1 can interact with each other, enhance PgFLC transcription and suppress FLOWERING LOCUS T (PgFT) transcription. Genetic evidence demonstrated that PgULT1 and PgLHP1 inhibit flowering by depositing H3K4me3 and H3K27me3 at the PgFLC and PgFT transcription start sites, respectively. PgULT1, PgDOF3.4 and PgLHP1 expression are suppressed under low temperatures, leading to reduced H3K4me3 and H3K27me3 modifications on PgFLC and PgFT promoters, thereby promoting flowering. Collectively, the functional interactions between epigenetic modifiers and transcription factors reveal a cooperative mechanism between TrxG and PcG to respond to low temperatures and promote flowering in P. grisea.