Strigolactone signaling repressor SMXL7 forms nuclear condensates to regulate gene transcription in Arabidopsis

Recent advancements in our understanding of gene expression highlight the role of phase-separated condensates in modulating transcriptional regulation. While the mechanisms of transcriptional condensate formation and function have been well characterized in animal systems, plant studies are still in the early stages. Here, we show that SUPPRESSOR OF MORE AXILLARY GROWTH 2-LIKE 7 (SMXL7), a repressor of plant hormone strigolactone (SL) signaling, forms phase-separated nuclear condensates. As expected, SMXL7 enriches its interacting proteins, SL receptor DWARF14 (D14) and F box protein MORE AXILLARY GROWTH 2 (MAX2), within the condensates. Intrinsically disordered regions in SMXL7 are essential for condensate formation and transcription repression. Significantly, SMXL7 nuclear condensates act as active transcriptional repressors by sequestering transcription factors, such as DNAJ DOMAIN-CONTAINING PROTEIN 1 (DNAJ1), away from gene loci, thereby regulating plant development. Our findings provide evidence that SMXL7-formed condensates sequester certain cellular components to repress transcription in planta and suggest a novel mode of SL signal transduction.