Polyploidy (genome duplication) is a pivotal force in evolution. However, the interactions between parental genomes in a polyploid nucleus, frequently involving subgenome dominance, are poorly understood. Here we showcase analyses of a bamboo system (Poaceae: Bambusoideae) comprising a series of lineages from diploid (herbaceous) to tetraploid and hexaploid (woody), with 11 chromosome-level de novo genome assemblies and 476 transcriptome samples. We find that woody bamboo subgenomes exhibit stunning karyotype stability, with parallel subgenome dominance in the two tetraploid clades and a gradual shift of dominance in the hexaploid clade. Allopolyploidization and subgenome dominance have shaped the evolution of tree-like lignified culms, rapid growth and synchronous flowering characteristic of woody bamboos as large grasses. Our work provides insights into genome dominance in a remarkable polyploid system, including its dependence on genomic context and its ability to switch which subgenomes are dominant over evolutionary time.

多倍体（基因组重复）是进化的关键力量。然而，人们对多倍体核中亲本基因组之间的相互作用（通常涉及亚基因组优势）知之甚少。在这里，我们展示了对竹子系统（禾本科：Bambusoideae）的分析，该系统包含从二倍体（草本）到四倍体和六倍体（木本）的一系列谱系，具有 11 个染色体水平的从头基因组组装和 476 个转录组样本。我们发现木本竹亚基因组表现出惊人的核型稳定性，在两个四倍体进化枝中具有平行的亚基因组优势，而在六倍体进化枝中优势逐渐转移。异源多倍化和亚基因组优势塑造了木本竹作为大型草类的树状木质化秆的进化、快速生长和同步开花的特征。我们的工作提供了对一个非凡的多倍体系统中基因组优势的见解，包括它对基因组背景的依赖以及它在进化过程中切换哪些亚基因组占主导地位的能力。