Genomic and Epigenomic Coordination Maintains Subgenome Transcriptional Balance in Allotetraploid Brassica napus [ChIP-seq]

Allopolyploidization-induced "genome shock" poses severe challenges to subgenome stability. However, the mechanisms by which subgenomes achieve functional homeostasis through genomic and epigenomic regulation remain poorly understood. This study integrates multi-omics data from Brassica napus and its putative diploid progenitors to reveal that coordinated convergence of genomic and epigenomic plays a central role in maintaining subgenome functional homeostasis within allopolyploids. Here, we present the first comprehensive, high-quality epigenomic maps to date for the diploid Brassica rapa and Brassica oleracea. Comparative genomic analyses revealed that epigenomic reprogramming in A and C subgenomes of the allotetraploid drives convergent chromatin states, which substantially diminished expression divergence between homoeologous gene pairs. Notably, compared to the A subgenome, the C subgenome in the allotetraploid exhibits more pronounced sequence conservation of regulatory elements and epigenetic homeostasis. Furthermore, transcription factor binding sites (TFBSs) influenced by genomic variation in the A subgenome demonstrate convergent evolutionary patterns toward the C subgenome. This study provides novel insights into the coordinated convergence of genomic and epigenomic regulation between subgenomes in allotetraploid Brassica napus, demonstrating that allopolyploids resolve subgenomic conflicts through multi-layered regulatory networks. These findings establish a novel paradigm for elucidating the molecular basis of polyploidy advantages in crops and for enabling rational design of synthetic polyploids. Overall design: Chromatin Immunoprecipitation followed by seqencing (ChIP-seq) for histone modifications (H3K4me3, H3K4me1, H3K27me3 and H3K9me2) in young leaves of B. rapa and B. oleracea.