Genome Evolution in Allopolyploid Wheats: Evidence from Low Copy DNA Sequences

小行星9508686 许多植物物种，以及一些动物物种，起源于两个或两个以上祖先物种之间的杂交。 在许多情况下，每一个亲本（二倍体）物种的两套染色体都保留在杂交种中，从而成为四（异源多倍体）倍体生物。 我们许多常见的作物，如小麦、燕麦、棉花和烟草都是异源多倍体。 这些物种的进化可能会沿着二倍体物种所不具备的途径进行。 例如，已经提出异源多倍体比二倍体更有效地缓冲有害突变。 然而，追溯多倍体植物物种祖先的一个复杂之处在于，发现一些二倍体物种本身就是过去杂交的杂交衍生物。 正是由于这个原因，可以假设多倍体杂种是联合收割机结合多个亲本系。 蒙大拿州立大学的卢瑟·塔尔伯特博士和马修·拉文博士正在富有想象力地利用DNA分析的新方法来研究多倍体小麦的起源，特别是被命名为“B”基因组小麦的起源。 他们的工作建立在三个融合的研究企业上：1）在小麦每条染色体的两臂上开发基因的特异性标记; 2）使用缺乏特定染色体的多倍体小麦的育种群体（所谓的缺体系）; 3）寻找和维护在中东收集的野生二倍体小麦。 他们的研究将检验这样一个假设，即每个基因组实际上是来自几个祖先物种的染色体的复合物，如果是这样，那么来自哪些祖先。 在染色体上使用单拷贝或低拷贝数的核DNA标记应该证明适用于其他植物系统，以帮助解决多倍体的杂种起源问题。

9508686 Talbert Many plant species, and some animal species as well, have originated following hybridization between two or more progenitor species. In many cases, both sets of chromosomes in each of the parental (diploid) species are retained in the hybrid, which thus becomes a tetra(allopoly)ploid organism. Many of our common crop plants like wheat, oats, cotton, and tobacco are allopolyploids. The evolution of these species may proceed along pathways that are not open to diploid species. For instance, it has been suggested that allopolyploids are buffered against deleterious mutations more effectively than diploids. One complication in tracing the ancestry of polyploid plant species, however, lies in the finding that some diploid species are themselves hybrid derivatives of past crossings. It is for this reason that polyploid hybrids can be hypothesized to combine multiple parental lines. Drs. Luther Talbert and Matthew Lavin of Montana State University are making imaginative use of new methods of DNA analysis to study the origins of polyploid wheats, and in particular the group designated as 'B' genome wheats. Their work builds upon three converging research enterprises: 1) the development of specific markers of genes on the two arms of each chromosome in wheats; 2) the use of breeding stocks of polyploid wheats that lack a specific chromosome (so-called nullisomic lines); and 3) the search for and maintenance of wild diploid wheats collected in the Middle East. Their studies will test the hypothesis that each genome is actually a composite of chromosomes from several progenitor species, and if so, from which progenitors. The use of single or low copy-number nuclear DNA markers on chromosomes should prove adaptable to other plant systems, in helping to solve the problem of hybrid origins of polyploids.