PNAS：东北师大等解码四倍体小麦物种形成机制

东北师范大学，美国华盛顿大学，中科院遗传与发育研究所的研究人员通过分析四个新合成的异源四倍体小麦，解析四倍体小麦物种形成机制，有望于新植物育种，开发独特的小麦品种。相关文章发表于2013年11月11日的《PNAS》杂志上。

PNAS：东北师大等解码四倍体小麦物种形成机制

在植物进化过程中多倍体或全基因组复制是经常发生的，但是只有一小部分的全基因组复制能成功形成物种。其中新生多倍体建立的一个主要问题在于持续核型的不稳定性。

研究人员在新研究中探讨四倍体小麦异源多倍体物种形成，这是构建六倍体小麦的一个具有里程碑意义的事件。

研究结果表明，核型稳定性，结合编码基因的拷贝数变异，以及基因组重复序列的局部变化，也许有助于建立四倍体小麦成功物种。这将能用于植物育种，开发独特的小麦品种。

研究人员通过结合荧光与基因组原位杂交为基础的核型分析，解析了四个新合成的异源四倍体小麦，其基因组构成分别为SshSshAmAm，SlSlAA ， SbSbDD，以及AADD。

其中前两者虽然具有持续核型稳定性，但是SbSbDD和AADD出现了大量非整倍体和染色体重组，其父本亚基因组具有显著的染色体收益/丢失和重组差异特征。而且值得注意的是，在SshSshAmAm和SlSlAA染色质稳定系中出现了同源基因拷贝数变异和重复DNA局部基因组变化。

这些研究结果表明，新形成的异源四倍体小麦具有与天然四倍体小麦类似的基因组组合，并且本身就具有持续性染色体核型稳定性。这种特性再加上快速的基因拷贝数变异，将为建立四倍体小麦奠定基础。

作者简介

刘宝(Bao Liu)，教授，是东北师范大学遗传与细胞研究所教育部表观遗传重点实验室长江学者，其早年毕业于南京农业大学，主要从事植物基因组进化和利用远缘杂交及生物技术进行作物遗传改良的研究，在植物异源多倍体基因组进化和利用野生稻改良水稻等方面取得多项成果。研究成果受到国际权威的认可和好评，多篇论文已被国际同行广泛引用。

原文摘要：

Intrinsic karyotype stability and gene copy number variations may have laid the foundation for tetraploid wheat formation

Huakun Zhang, Yao Bian, Xiaowan Gou, Yuzhu Dong, Sachin Rustgi, Bangjiao Zhang,Chunming Xu, Ning Li, Bao Qi, Fangpu Han, Diter von Wettstein and Bao Liu

Polyploidy or whole-genome duplication is recurrent in plant evolution, yet only a small fraction of whole-genome duplications has led to successful speciation. A major challenge in the establishment of nascent polyploids is sustained karyotype instability, which compromises fitness. The three putative diploid progenitors of bread wheat, with AA, SS (S ∼ B), and DD genomes occurred sympatrically, and their cross-fertilization in different combinations may have resulted in fertile allotetraploids with various genomic constitutions. However, only SSAA or closely related genome combinations have led to the speciation of tetraploid wheats like Triticum turgidum and Triticum timopheevii. We analyzed early generations of four newly synthesized allotetraploid wheats with genome compositions SshSshAmAm, SlSlAA, SbSbDD, and AADD by combined fluorescence and genomic in situ hybridization-based karyotyping. Results of karyotype analyses showed that although SshSshAmAm and SlSlAA are characterized by immediate and persistent karyotype stability, massive aneuploidy and extensive chromosome restructuring are associated with SbSbDD and AADD in which parental subgenomes showed markedly different propensities for chromosome gain/loss and rearrangements. Although compensating aneuploidy and reciprocal translocation between homeologs prevailed, reproductive fitness was substantially compromised due to chromosome instability. Strikingly, localized genomic changes in repetitive DNA and copy-number variations in gene homologs occurred in both chromosome stable lines, SshSshAmAm and SlSlAA. Our data demonstrated that immediate and persistent karyotype stability is intrinsic to newly formed allotetraploid wheat with genome combinations analogous to natural tetraploid wheats. This property, coupled with rapid gene copy-number variations, may have laid the foundation of tetraploid wheat establishment.