Phase separation of HRLP regulates flowering time in .

RNA binding proteins mediate posttranscriptional RNA metabolism and play regulatory roles in many developmental processes in eukaryotes. Despite their known effects on the floral transition from vegetative to reproductive growth in plants, the underlying mechanisms remain largely obscure. Here, we show that a hitherto unknown RNA binding protein, hnRNP R-LIKE PROTEIN (HRLP), inhibits cotranscriptional splicing of a key floral repressor gene (). This, in turn, facilitates R-loop formation near intron I to repress its transcription, thereby promoting the floral transition in . HRLP, together with the splicing factor ARGININE/SERINE-RICH 45, forms phase-separated nuclear condensates with liquid-like properties, which is essential for HRLP function in regulating splicing, R-loop formation, and RNA Polymerase II recruitment. Our findings reveal that inhibition of cotranscriptional splicing of by nuclear HRLP condensates constitutes the molecular basis for down-regulation of transcript levels to ensure the reproductive success of .