Alix Karine, Gérard Pierre R, Schwarzacher Trude, Heslop-Harrison J S Pat
GQE - Le Moulon, INRA, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91190 Gif-sur-Yvette, France.
Department of Genetics and Genome Biology, University of Leicester, Leicester, UK.
Ann Bot. 2017 Aug 1;120(2):183-194. doi: 10.1093/aob/mcx079.
Polyploidy or whole-genome duplication is now recognized as being present in almost all lineages of higher plants, with multiple rounds of polyploidy occurring in most extant species. The ancient evolutionary events have been identified through genome sequence analysis, while recent hybridization events are found in about half of the world's crops and wild species. Building from this new paradigm for understanding plant evolution, the papers in this Special Issue address questions about polyploidy in ecology, adaptation, reproduction and speciation of wild and cultivated plants from diverse ecosystems. Other papers, including this review, consider genomic aspects of polyploidy.
Discovery of the evolutionary consequences of new, evolutionarily recent and ancient polyploidy requires a range of approaches. Large-scale studies of both single species and whole ecosystems, with hundreds to tens of thousands of individuals, sometimes involving 'garden' or transplant experiments, are important for studying adaptation. Molecular studies of genomes are needed to measure diversity in genotypes, showing ancestors, the nature and number of polyploidy and backcross events that have occurred, and allowing analysis of gene expression and transposable element activation. Speciation events and the impact of reticulate evolution require comprehensive phylogenetic analyses and can be assisted by resynthesis of hybrids. In this Special Issue, we include studies ranging in scope from experimental and genomic, through ecological to more theoretical.
The success of polyploidy, displacing the diploid ancestors of almost all plants, is well illustrated by the huge angiosperm diversity that is assumed to originate from recurrent polyploidization events. Strikingly, polyploidization often occurred prior to or simultaneously with major evolutionary transitions and adaptive radiation of species, supporting the concept that polyploidy plays a predominant role in bursts of adaptive speciation. Polyploidy results in immediate genetic redundancy and represents, with the emergence of new gene functions, an important source of novelty. Along with recombination, gene mutation, transposon activity and chromosomal rearrangement, polyploidy and whole-genome duplication act as drivers of evolution and divergence in plant behaviour and gene function, enabling diversification, speciation and hence plant evolution.
多倍体或全基因组复制如今被认为几乎存在于所有高等植物谱系中，大多数现存物种都经历了多轮多倍体化。通过基因组序列分析已确定了古老的进化事件，而在世界上约一半的作物和野生物种中发现了近期的杂交事件。基于这种理解植物进化的新范式，本期特刊中的论文探讨了多倍体在来自不同生态系统的野生和栽培植物的生态、适应、繁殖和物种形成方面的问题。其他论文，包括本综述，考虑了多倍体的基因组方面。
发现新的、近期进化的和古老的多倍体的进化后果需要一系列方法。对单个物种和整个生态系统进行大规模研究，涉及数百到数万个个体，有时包括“花园”或移植实验，对于研究适应性很重要。需要对基因组进行分子研究，以测量基因型的多样性，显示祖先、发生的多倍体和回交事件的性质和数量，并允许分析基因表达和转座元件激活。物种形成事件和网状进化的影响需要全面的系统发育分析，杂种的重新合成可以提供帮助。在本期特刊中，我们纳入了从实验和基因组学、生态学到更多理论性的研究。
多倍体取代了几乎所有植物的二倍体祖先并取得成功，这在假定源自反复多倍体化事件的巨大被子植物多样性中得到了很好的体现。引人注目的是，多倍体化通常发生在物种的主要进化转变和适应性辐射之前或同时，支持了多倍体在适应性物种形成爆发中起主要作用的概念。多倍体导致立即的基因冗余，并随着新基因功能的出现，成为新特性的重要来源。与重组、基因突变、转座子活性和染色体重排一起，多倍体和全基因组复制是植物行为和基因功能进化和分化的驱动力，促进了多样化、物种形成以及植物进化。
