Pan-genomic and transcriptomic analyses reveal subfunctionalization of CBP/p300-like histone acetyltransferases in soybean seed development.

Background

Soybean is a crucial global source of protein and oil. The CBP/p300 histone acetyltransferases (HACs) are key transcriptional regulators, yet their diversity and functions in soybean remain unexplored at a pan-genomic level.

Results

Here, we constructed a pan-genomic resource for the HAC gene family across 29 wild, landrace, and cultivated soybean accessions, identifying 142 HAC genes. These genes are confined to chromosomes 7, 8, 15, and 19, indicating strong evolutionary constraints. Phylogenetic analysis divided HACs into five subgroups with distinct domain architectures: Group 4-5 retain full CBP/p300 domains, whereas Group 1-3 show progressive domain loss. Pan-transcriptomic analyses revealed an expression dichotomy: Group 3-5 are broadly expressed, while Group 1-2 exhibit endosperm-specific expression during early seed development, suggesting specialized roles in nutrient transfer and embryogenesis. Notably, elite cultivars (e.g., Wm82, ZH13) have lost Group 2 homologs preserved in wild soybeans, highlighting domestication-driven erosion of epigenetic diversity. Co-expression network analysis prioritized Wm82-HAC1 (Group 1) as a candidate gene coordinating nutrient metabolism and seed maturation pathways.

Conclusion

Our study provides the first comprehensive panorama of epigenetic regulators in the soybean pan-genome. Our findings reveal how subfunctionalization and domestication help shape the HAC regulatory network in soybean, highlighting wild germplasm as a valuable reservoir for recovering lost alleles (Group2 homologs) and identifying Wm82-HAC1 (Group 1) as a prime target for precision breeding of seed traits.