Single-Copy Sequence Evolution, Polyploidy and Phylogeny Reconstruction

[508630]温德尔染色体加倍或多倍体是植物中常见的自然现象。超过三分之二的植物物种被怀疑在它们的进化史上经历过一次或多次染色体加倍，包括许多经济上重要的物种，如小麦、马铃薯、棉花、大豆和甘蔗。染色体加倍与亲缘物种间的杂交密切相关。多倍体的一个后果是所有的染色体，以及基因，在新的基因组中被复制，从而产生了“基因冗余”。据推测，这种冗余导致了新的基因功能，因为每个基因的一个拷贝可以自由改变，而另一个保持其原始功能。或者，可能其中一个复制的拷贝由于突变而丢失，或者可能两个拷贝都保持原有的功能。人们对这些过程在自然界中运作的程度或它们的相对频率知之甚少。爱荷华州立大学的乔纳森·温德尔博士正在研究这个问题：多倍体植物中基因的复制会发生什么？利用分子生物学的工具和棉花属的二倍体和多倍体模型系统，对重复基因进行分离、测序和相互比较，并与它们的非多倍体祖先类型的拷贝进行比较。将从不同的染色体上研究许多不同类型的基因，目的是发现指导多倍体中复制基因命运的一般原理。本研究的结果也将有助于指导核基因的选择，用于密切相关的种和属的系统发育分析。

9508630 Wendel A common natural phenomenon in plants is chromosome doubling or polyploidy. More than two-thirds of all plant species are suspected of having passed through one or more rounds of chromosome doubling during their evolutionary history, including many economically important species such as the wheat, potato, cotton, soybean, and sugar cane. Chromosome doubling is highly correlated with hybridization between closely related species. One consequence of polyploidy is that all chromosomes, and hence genes, become duplicated in the new genome, thereby creating "genetic redundancy". It has been hypothesized that this redundancy leads to new gene functions, because one copy of each gene is free to change while the other retains its original function. Alternatively, perhaps one of the duplicated copies is lost through mutation, or perhaps both copies maintain the original function. There is very little known about the extent to which these processes operate in nature or their relative frequency. Dr. Jonathan Wendel of Iowa State University is addressing the question, What happens to duplicated copies of genes in polyploid plants? Using tools of molecular biology and a model system of diploids and polyploids from the cotton genus, Gossypium, duplicated genes will be isolated, sequenced, and compared to each other as well as to copies from their non-polyploid ancestral types. Many different types of genes will be studied from different chromosomes with the aim of discovering general principles that guide the fate of duplicated genes in polyploids. Results from this research will also help guide the choice of nuclear genes used for phylogenetic analysis of closely related species and genera.