The chromatin reader MBD4 regulates temperature- and flowering-responsive transcription by recognizing histone arginine methylation.

Precise regulation of flowering time in plants is achieved through tight transcriptional control of master regulators, which is fine-tuned by dynamic histone modifications and changes in chromatin structure. In our search for flowering-related regulatory networks, we identified METHYL-BINDING DOMAIN PROTEIN 4 (MBD4) as a key hub controlling flowering and responses to high ambient temperature in Brassica napus and Arabidopsis. While MBD4 was previously described as a DNA methylation reader, our findings reveal that MBD4 recognizes histone arginine methylation. The MBD4 genome-wide distribution and its coordinated expression with histone methylation writers coincide with global patterns of arginine methylation. Although histone lysine methylation is well understood, the role of arginine methylation remains largely unexplored. Our results demonstrate that MBD4 plays a critical role in the transcriptional control of flowering regulators by recognizing arginine methylation and facilitating acetylation removal. Additionally, we confirmed the significance of the Brassica napus MBD4 homeolog in modulating the transition to the reproductive phase through chromatin alterations at the BnaFLC and BnaMAF4 loci, suggesting that chromatin readers may have a global influence on important developmental traits in crops. Overall, understanding these molecular mechanisms is highly relevant to developing strategies to improve crop adaptation to global warming.