Genomic Asymmetry for Morphology in Allopolyploids Within and out of Brassica

The genomic asymmetry in the nonrandom retention and expression of controlling genes for some traits from one.parental diploid is obvious in some natural and synthetic allopolyploids, and has the evolutionary implications. Here we review.the genomic asymmetry for the morphological performance in three cultivated Brassica allotetraploids and some intergeneric.allopolyploids within Brassicaceae species. For the phenotypic biases of Brassica allotetraploids, Brassica oleracea (genomes.CC) is dominant over B. nigra (BB) and B. rapa (AA) in B. carinata (CCBB) and B. napus (CCAA), respectively, and B. nigra is.dominant over B. rapa in B. juncea (BBAA), showing the C>B>A dominance hierarchy. However, the morphology of several.Brassica species including B. oleracea at top dominance is largely recessive in their intergeneric hybrids and allopolyploids with.other crucifers, such as Raphanus sativus, Orychophragmus violaceus. The morphology of Arabidopsis thaliana is also recessive.in its two allotetraploids. Among the dominant features, the leaf serration is expressed consistently in these intergeneric and.Arabidopsis allopolyploids. The phenotype expression of the recessive diploid is subject to the euploidy or aneuploidy state of its.genome, and the dominant traits are still mostly expressed in the aneuploidy state of their genome. The morphological biases in.these allopolyploids are discussed in the contexts of the genomic structure and interplay.

在一些天然和人工合成的异源多倍体中，来自一个亲本二倍体的某些性状控制基因的非随机保留和表达所呈现的基因组不对称性是明显的，并且具有进化意义。在此我们综述了三种栽培的芸薹属异源四倍体以及十字花科一些属间异源多倍体在形态表现上的基因组不对称性。对于芸薹属异源四倍体的表型偏向，在埃塞俄比亚芥（CCBB）和欧洲油菜（CCAA）中，甘蓝（CC基因组）分别对黑芥（BB）和芜菁（AA）占优势，在芥菜（BBAA）中黑芥对芜菁占优势，呈现出C > B > A的优势等级。然而，包括处于最高优势的甘蓝在内的几种芸薹属植物的形态在它们与其他十字花科植物如萝卜、诸葛菜的属间杂种和异源多倍体中在很大程度上是隐性的。拟南芥的形态在它的两个异源四倍体中也是隐性的。在显性特征中，叶片锯齿在这些属间和拟南芥异源多倍体中持续表达。隐性二倍体的表型表达受其基因组的整倍性或非整倍性状态的影响，并且显性性状在其基因组的非整倍性状态下大多仍然能够表达。这些异源多倍体中的形态偏向在基因组结构和相互作用的背景下进行了讨论。