The MBD4 chromatin reader regulates transcription related to temperature and flowering responses through recognition of histone arginine methylation in Arabidopsis thaliana and Brassica napus

Precise regulation of flowering time in plants is achieved through the tight transcriptional control of master regulators, fine-tuned by the dynamics of histone modifications and structural chromatin alterations. In our search for flowering-related gene networks, we identified METHYL-BINDING DOMAIN PROTEIN 4 (MBD4) as a crucial hub for flowering and high ambient temperature responses in Brassica napus and Arabidopsis. While previously described as a DNA methylation reader, our findings reveal that MBD4 recognises histone arginine methylation. MBD4 genome-wide distribution and coordinated expression with histone methylation writers match arginine methylation global patterns. 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 recognising arginine methylation and facilitating acetylation erasure. Additionally, we confirmed the significance of the Brassica napus MBD4 homeolog in modulating the reproductive phase switch 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 extremely relevant regarding strategies that improve crop adaptation to global warming.