Chromosome number is key to longevity of polyploid lineages
Chromosome number is key to longevity of polyploid lineages
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DOI：
10.1111/nph.17361
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发表时间：
2021-04-25
期刊：
影响因子：
9.4
通讯作者：
Paterson, Andrew H.
中科院分区：
文献类型：
--
作者：
Bowers, John E.;Paterson, Andrew H.
多倍体在植物谱系中普遍存在，并且经常递归，最常见的是导致灭绝，但偶尔与巨大的进化成功有关。然而，大多数被子植物物种的染色体数目并没有因为多倍性而呈指数增长，而是少于14对。在基因组复制之后，二倍体化可以使必需基因的一个拷贝失去功能而没有适应性成本。在孤立的亚群中，交替（同源）基因拷贝可能丢失，产生不相容性，降低亚群之间杂交的适应性，限制有利的遗传变化的交换，降低物种适应性。当多组不相容的基因在遗传上相连时，它们的有害影响就不是独立的。杂种中独立作用的不亲和基因座组的有效数目受到染色体数目和重组的限制。因此，具有许多染色体的物种在二倍体化期间受到更高的适应度惩罚。减少基因流动的核型变化，尤其是融合，通常是适应性劣势，但在二倍体化过程中，可以通过减少差异二倍体化等位基因的混合来增加适应性。由二倍体化引起的适合度惩罚有利于加速核型变化，每一种变化都增加了基因流动的障碍，有助于物种形成。较低的染色体数目和增加的染色体融合赋予优势，通过独立的机制，在多倍体形成后的二倍体化过程中存活。
Polyploidy is ubiquitous and often recursive in plant lineages, most frequently resulting in extinction but occasionally associated with great evolutionary success. However, instead of chromosome numbers exponentially increasing due to recurrent polyploidy, most angiosperm species have fewer than 14 chromosome pairs. Following genome duplication, diploidisation can render one copy of essential genes nonfunctional without fitness cost. In isolated subpopulations, alternate (homoeologous) gene copies can be lost, creating incompatibilities that reduce fitness of hybrids between subpopulations, constraining exchange of favourable genetic changes and reducing species fitness. When multiple sets of incompatible genes are genetically linked, their deleterious effects are not independent. The effective number of independently acting sets of incompatible loci in hybrids is limited by chromosome number and recombination. Therefore, species with many chromosomes are subject to a higher fitness penalty during diploidisation. Karyotypic changes, especially fusions, that reduce gene flow are normally fitness disadvantages, but during the diploidisation process, can increase fitness by reducing mixing of differentially diploidised alleles. Fitness penalties caused by diploidisation favour accelerated karyotypic change, with each change increasing barriers to gene flow, contributing to speciation. Lower chromosome numbers and increased chromosome fusions confer advantages to surviving the diploidisation process following polyploid formation, by independent mechanisms.