植物异源多倍体中特定染色体组的剥离与重建

Extraction and reconstruction of constituent genomes from allopolyploid plants

由于异源多倍体物种的进化时间久远,难以知晓确切的二倍体亲本,现在推测的自然界现存二倍体种又经历过独立的演化,因此,通过特定的实验方法从天然的异源多倍体物种中剥离出特定染色体组并重建异源多倍体的基本种,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材料。现已通过不同的杂交策略,从异源六倍体普通小麦和异源四倍体种甘蓝型油菜中成功重建它们的一个基本种。例如以人工合成的芸薹属异源六倍体(如埃塞俄比亚芥与白菜杂交的AA.BBCC)为桥梁,其中的C染色体组被选择性的丢失后产生的芥菜型油菜(AA.BB)与埃塞俄比亚芥杂交形成的杂种(BBAC)自交后便可重建黑芥(BB)祖先种;将四倍体与二倍体种之一杂交后形成的同源异源六倍体(如AAAACC)连续自交,使处于同源四倍体状态的染色体组(A)快速丢失而重建另一个二倍体基本种(CC)。

Diploid parents of allopolyploid species are difficult to identify due to their long history of evolution,and the extant of their presumable parents in nature experienced independent evolution. To understand the genetic contributions and interplay for the allopolyploidy species,particular experimental programs are needed to extract their constituent genomes and reconstruct their progenitors. Different crossing strategies were successfully adopted on progenitor restitution from allohexaploid bread wheat and allopolyploid Brassica napus. For example,through the synthesis of Brassica allohexaploid（ AA. BBCC from B. rapa × B. carinata）,ancestral B. nigra（ BB） was restituted followed by preferential elimination of C genome in B. juncea（ AA. BB）,and by hybridization of B. juncea（ AA.BB） to B. carinata,and then by selfing the hybrid（ BBAC） thereafter. Another example,ancestral diploid parent（ CC） was restituted followed by the first synthesis of auto-allo-polyploids（ e. g. AAAACC） between the allotetraploid and one of extant diploid parent,and then the loss of A chromosome from tetraploid-state genome during selfing generations.