Department of Systematic and Evolutionary Botany, University of Vienna, Rennweg 14, A-1030, Vienna, Austria.
BMC Evol Biol. 2013 Jul 3;13:136. doi: 10.1186/1471-2148-13-136.
Prospero (Hyacinthaceae) provides a unique system to assess the impact of genome rearrangements on plant diversification and evolution. The genus exhibits remarkable chromosomal variation but very little morphological differentiation. Basic numbers of x = 4, 5, 6 and 7, extensive polyploidy, and numerous polymorphic chromosome variants were described, but only three species are commonly recognized: P. obtusifolium, P. hanburyi, and P. autumnale s.l., the latter comprising four diploid cytotypes. The relationship between evolutionary patterns and chromosomal variation in diploids, the basic modules of the extensive cytological diversity, is presented.
Evolutionary inferences were derived from fluorescence in situ hybridization (FISH) with 5S and 35S rDNA, genome size estimations, and phylogenetic analyses of internal transcribed spacer (ITS) of 35S rDNA of 49 diploids in the three species and all cytotypes of P. autumnale s.l. All species and cytotypes possess a single 35S rDNA locus, interstitial except in P. hanburyi where it is sub-terminal, and one or two 5S rDNA loci (occasionally a third in P. obtusifolium) at fixed locations. The localization of the two rDNA types is unique for each species and cytotype. Phylogenetic data in the P. autumnale complex enable tracing of the evolution of rDNA loci, genome size, and direction of chromosomal fusions: mixed descending dysploidy of x = 7 to x = 6 and independently to x = 5, rather than successive descending dysploidy, is proposed.
All diploid cytotypes are recovered as well-defined evolutionary lineages. The cytogenetic and phylogenetic approaches have provided excellent phylogenetic markers to infer the direction of chromosomal change in Prospero. Evolution in Prospero, especially in the P. autumnale complex, has been driven by differentiation of an ancestral karyotype largely unaccompanied by morphological change. These new results provide a framework for detailed analyses of various types of chromosomal rearrangements and karyotypic variation in polyploids.
普罗波斯（秋水仙科）为评估基因组重排对植物多样化和进化的影响提供了一个独特的系统。该属表现出显著的染色体变异，但形态分化很小。描述了基本基数 x=4、5、6 和 7、广泛的多倍体以及许多多态性染色体变体，但仅公认三种物种：P. obtusifolium、P. hanburyi 和 P. autumnale s.l.，后者包括四个二倍体细胞型。呈现了二倍体中进化模式和染色体变异之间的关系，这是广泛细胞学多样性的基本模块。
通过荧光原位杂交（FISH）与 5S 和 35S rDNA、基因组大小估计以及 35S rDNA 的内部转录间隔区（ITS）的系统发育分析，从三个物种的 49 个二倍体和 P. autumnale s.l.的所有细胞型中得出进化推论。所有物种和细胞型都具有单个 35S rDNA 基因座，除了 P. hanburyi 中外切，其余均为间位，以及一个或两个 5S rDNA 基因座（在 P. obtusifolium 中偶尔为第三个）位于固定位置。两种 rDNA 类型的定位对于每个物种和细胞型都是独特的。P. autumnale 复合体中的系统发育数据使 rDNA 基因座、基因组大小和染色体融合方向的进化得以追踪：提出了从 x=7 到 x=6 和独立于 x=5 的混合下降非整倍体，而不是连续下降非整倍体。
所有二倍体细胞型都被恢复为明确的进化谱系。细胞遗传学和系统发育方法为推断普罗波斯染色体变化的方向提供了极好的系统发育标记。普罗波斯的进化，特别是 P. autumnale 复合体的进化，是由一个主要没有形态变化的祖先染色体组的分化驱动的。这些新结果为详细分析多倍体中的各种类型的染色体重排和核型变异提供了框架。
