异源四倍体埃塞俄比亚芥中祖先染色体组的剥离及遗传研究

As the precise diploid parents of the allopolyploid species are unknown, and the presumable extant ancestors in nature have experienced independent evolution, the extraction of their constituent genomes and then reconstruction of the progenitors by particular experimental programs should provide unique avenues and materials to study their genetic contributions and interplay for the allopolyploidy speciation. In this project, via two crossing strategies, the ancestral subgenomes will be extracted from the one of three cultivated Brassica allotetraploids Brassica carinata (BBCC) to restitute the two progenitors B. nigra (BB) and B. oleracea (CC). Then the comparative characterizations between B. carinata and its two reconstructed diploids are made for the phenotype, genome, transcriptome and epigenetics, to unravel the genetic regulation and interaction between two ancestral genomes and to give new insights into the genetics of allopolyploidy evolution.

由于异源多倍体物种的进化时间久远而难以知晓确切的祖先亲本、现在推测的自然界现存的祖先种经历了独立演化，故通过特定的实验方法从天然的异源多倍体物种中剥离出祖先染色体组并重建祖先种，将为研究异源多倍化过程中祖先基因组的遗传与互作提供独特的途径与材料。本项目拟通过两种杂交途径，从三个芸苔属栽培异源四倍体种之一的埃塞俄比亚芥(BBCC)中剥离出两个祖先染色体组并重新组建黑芥(BB)与甘蓝(CC)祖先种，然后在表型、基因组、转录组、表观遗传等方面与四倍体种进行比较分析，以揭示来自亲缘关系较远的两个祖先的基因组的遗传调节与互作，为多倍体的遗传与进化研究提供新材料与新知识。

本项目通过两种杂交途径，拟从芸苔属异源四倍体种埃塞俄比亚芥(BBCC)中剥离出两个祖先染色体组并重建黑芥(BB)与甘蓝(CC)祖先种, 以研究其进化中祖先基因组的遗传与互作。首先，将埃塞俄比亚芥(BBCC)与白菜（AA）杂交形成的异源六倍体（BBCC .AA）自交丢失全部的C 染色体组后衍生的新芥菜型油菜AA.BB与原埃芥亲本杂交，期望从杂种（BBAC）自交后代中获得只包含黑芥染色体组成的植株，即重建的黑芥祖先； 但该杂种自交后代具有较高的染色体数目，可能是配子中仍有较多的A与C基因组染色体，故未能实现黑芥祖先的重建。其次，将埃芥分别与甘蓝和黑芥杂交后产生两个杂种（BCC，BBC）、染色体加倍后形成两个同源异源六倍体（BBCCCC，BBBBCC），处于同源四倍体状态的染色体组，而剥离出黑芥与甘蓝两个先种；自交后产生了整倍体与非整倍体后代，非整倍体植株只丢失了少数染色体，因四倍体状态的B、C基因组染色体配对形成的四价体很少、而大多配对成二价体，后期分离也较正常，故也未能剥离两个祖先种。