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首页> 外文期刊>Annals of Botany >A bicontinental origin of polyploid Australian/New Zealand Lepidium species (Brassicaceae)? Evidence from genomic in situ hybridization.
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A bicontinental origin of polyploid Australian/New Zealand Lepidium species (Brassicaceae)? Evidence from genomic in situ hybridization.

机译：多倍体澳大利亚/新西兰的Le属物种（十字花科）的双大陆起源？来自基因组原位杂交的证据。

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Incongruence between chloroplast and nuclear DNA phylogenies, and single additive nucleotide positions in internal transcribed spacer (ITS) sequences of polyploid Australian/New Zealand (NZ) Lepidium species have been used to suggest a bicontinental hybrid origin. This pattern was explained by two trans-oceanic dispersals of Lepidium species from California and Africa and subsequent hybridization followed by homogenization of the ribosomal DNA sequence either to the Californian (C-clade) or to the African ITS-type (A-clade) in two different ITS-lineages of Australian/NZ Lepidium polyploids. METHODS: Genomic in situ hybridization (GISH) was used to unravel the genomic origin of polyploid Australian/NZ Lepidium species. Fluorescence in situ hybridization (FISH) with ribosomal DNA (rDNA) probes was applied to test the purported ITS evolution, and to facilitate chromosome counting in high-numbered polyploids. KEY RESULTS: In Australian/NZ A-clade Lepidium polyploids, GISH identified African and Australian/NZ C-clade species as putative ancestral genomes. Neither the African nor the Californian genome were detected in Australian/NZ C-clade species and the Californian genome was not detected in Australian/NZ A-clade species. Five of the eight polyploid species (from 7x to 11x) displayed a diploid-like set of rDNA loci. Even the undecaploid species Lepidium muelleriferdinandi (2n = 11x = 88) showed only one pair of each rDNA repeat. In A-clade allopolyploids, in situ rDNA localization combined with GISH corroborated the presence of the African ITS-type. CONCLUSIONS: The nuclear genomes of African and Australian/NZ C-clade species were detected by GISH in allopolyploid Australian/NZ Lepidium species of the A-clade, supporting their hybrid origin. The presumed hybrid origin of Australian/NZ C-clade taxa could not be confirmed. Hence, it is assumed that Californian ancestral taxa experienced rapid radiation in Australia/NZ into extant C-clade polyploid taxa followed by hybridization with African species. As a result, A-clade allopolyploid Lepidium species share the Californian chloroplast type and the African ITS-type with the C-clade Australian/NZ polyploid and African diploid species, respectively.
机译：叶绿体和核DNA系统发育之间的不一致性，以及多倍体澳大利亚/新西兰（NZ）鳞翅目物种的内部转录间隔区（ITS）序列中的单个加成核苷酸位置已被用于暗示双大陆杂种起源。这种模式的解释是来自加利福尼亚和非洲的两次跨洋性的Lepidium物种扩散，随后杂交，随后核糖体DNA序列均质化为Californian（C-clade）或非洲ITS型（A-clade）。澳大利亚/新西兰的Lepidium多倍体有两个不同的ITS谱系。方法：基因组原位杂交（GISH）被用来揭示多倍体澳大利亚/新西兰Lepidium物种的基因组起源。用核糖体DNA（rDNA）探针进行荧光原位杂交（FISH），以测试声称的ITS进化，并促进高倍数多倍体中的染色体计数。关键结果：在澳大利亚/新西兰A进化族的Lepidium多倍体中，GISH将非洲和澳大利亚/新西兰C进化族确定为推定的祖先基因组。在澳大利亚/新西兰C族物种中均未检测到非洲和加利福尼亚基因组，在澳大利亚/ NZ A族物种中未检测到加利福尼亚基因组。八个多倍体物种中的五个（从7x到11x）显示了二倍体样的rDNA基因座。甚至非十倍体物种Lepidium muelleriferdinandi（2n = 11x = 88）的每个rDNA重复序列也只有一对。在A族异源多倍体中，原位rDNA定位与GISH结合证实了非洲ITS型的存在。结论：通过GISH在A-进化枝的同种多倍体澳大利亚/ NZ Lepidium物种中检测到了非洲和澳大利亚/ NZ C进化枝种的核基因组，支持了它们的杂种起源。无法确定澳大利亚/新西兰C-clad类群的杂种起源。因此，可以认为加利福尼亚的祖先分类群在澳大利亚/新西兰经历了快速辐射，进入现存的C进化多倍体分类群，然后与非洲物种杂交。结果，A进化的同种多倍体的鳞翅目物种与C进化的澳大利亚/ NZ的多倍体和非洲的二倍体物种共享加利福尼亚的叶绿体类型和非洲的ITS类型。

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