Mason Annaliese S, Wendel Jonathan F
Plant Breeding Department, Justus Liebig University Giessen, Giessen, Germany.
Ecology, Evolution, and Organismal Biology Department, Iowa State University, Ames, IA, United States.
Front Genet. 2020 Aug 28;11:1014. doi: 10.3389/fgene.2020.01014. eCollection 2020.
Polyploidy is a major force in plant evolution and speciation. In newly formed allopolyploids, pairing between related chromosomes from different subgenomes (homoeologous chromosomes) during meiosis is common. The initial stages of allopolyploid formation are characterized by a spectrum of saltational genomic and regulatory alterations that are responsible for evolutionary novelty. Here we highlight the possible effects and roles of recombination between homoeologous chromosomes during the early stages of allopolyploid stabilization. Homoeologous exchanges (HEs) have been reported in young allopolyploids from across the angiosperms. Although all lineages undergo karyotype change via chromosome rearrangements over time, the early generations after allopolyploid formation are predicted to show an accelerated rate of genomic change. HEs can also cause changes in allele dosage, genome-wide methylation patterns, and downstream phenotypes, and can hence be responsible for speciation and genome stabilization events. Additionally, we propose that fixation of duplication - deletion events resulting from HEs could lead to the production of genomes which appear to be a mix of autopolyploid and allopolyploid segments, sometimes termed "segmental allopolyploids." We discuss the implications of these findings for our understanding of the relationship between genome instability in novel polyploids and genome evolution.
多倍体是植物进化和物种形成的主要驱动力。在新形成的异源多倍体中，减数分裂期间来自不同亚基因组的相关染色体（同源染色体）之间的配对很常见。异源多倍体形成的初始阶段的特征是一系列跳跃式的基因组和调控改变，这些改变导致了进化上的新奇性。在这里，我们强调了同源染色体之间重组在异源多倍体稳定化早期阶段可能产生的影响和作用。同源交换（HEs）已在被子植物的年轻异源多倍体中被报道。尽管所有谱系都会随着时间的推移通过染色体重排发生核型变化，但预计异源多倍体形成后的早期世代会出现加速的基因组变化速率。同源交换还会导致等位基因剂量、全基因组甲基化模式和下游表型的变化，因此可能是物种形成和基因组稳定事件的原因。此外，我们提出，由同源交换导致的重复 - 缺失事件的固定可能会产生看起来是同源多倍体和异源多倍体片段混合的基因组，有时被称为“区段异源多倍体”。我们讨论了这些发现对于我们理解新多倍体中的基因组不稳定性与基因组进化之间关系的意义。
