Department of Biomedicine and Biotechnology, University of Alcalá, Alcalá de Henares, Madrid, Spain.
PLoS One. 2021 Oct 15;16(10):e0257100. doi: 10.1371/journal.pone.0257100. eCollection 2021.
Cytogenetic observations, phylogenetic studies and genome analysis using high-density genetic markers have suggested a tetraploid Avena species carrying the C and D genomes (formerly C and A) to be the donor of all hexaploid oats (AACCDD). However, controversy surrounds which of the three extant CCDD tetraploid species-A. insularis, A. magna and A. murphyi-is most closely related to hexaploid oats. The present work describes a comparative karyotype analysis of these three CCDD tetraploid species and two hexaploid species, A. sativa and A. byzantina. This involved the use of FISH with six simple sequence repeats (SSRs) with the motifs CT, AAC, AAG, ACG, ATC and ACT, two repeated ribosomal sequences, and C genome-specific repetitive DNA. The hybridization pattern of A. insularis with oligonucleotide (AC)10 was also determined and compared with those previously published for A. sativa and A. byzantina. Significant differences in the 5S sites and SSR hybridization patterns of A. murphyi compared to the other CCDD species rule out its being directly involved in the origin of the hexaploids. In contrast, the repetitive and SSR hybridization patterns shown by the D genome chromosomes, and by most of the C genome chromosomes of A. magna and A. insularis, can be equated with the corresponding chromosomes of the hexaploids. Several chromosome hybridization signals seen for A. insularis, but not for A. magna, were shared with the hexaploid oats species, especially with A. byzantina. These diagnostic signals add weight to the idea that the extant A. insularis, or a direct ancestor of it, is the most closely related progenitor of hexaploid oats. The similarity of the chromosome hybridization patterns of the hexaploids and CCDD tetraploids was taken as being indicative of homology. A common chromosome nomenclature for CCDD species based on that of the hexaploid species is proposed.
细胞遗传学观察、系统发育研究和利用高密度遗传标记进行的基因组分析表明，携带 C 和 D 基因组（以前称为 C 和 A）的四倍体燕麦物种是所有六倍体燕麦（AACCDD）的供体。然而，关于现存的三个 CCDD 四倍体物种——A. insularis、A. magna 和 A. murphyi——中哪一个与六倍体燕麦最为密切相关，存在争议。本研究描述了这三个 CCDD 四倍体物种和两个六倍体物种 A. sativa 和 A. byzantina 的比较核型分析。这涉及使用六个简单序列重复（SSR）的 FISH 分析，SSR 的基序为 CT、AAC、AAG、ACG、ATC 和 ACT，两个重复核糖体序列，以及 C 基因组特异性重复 DNA。还确定了 A. insularis 与寡核苷酸（AC）10 的杂交模式，并将其与之前发表的 A. sativa 和 A. byzantina 的杂交模式进行了比较。与其他 CCDD 物种相比，A. murphyi 的 5S 位点和 SSR 杂交模式的显著差异排除了它直接参与六倍体起源的可能性。相比之下，A. magna 和 A. insularis 的 D 基因组染色体以及大多数 C 基因组染色体显示的重复和 SSR 杂交模式，可以与六倍体的相应染色体相媲美。在 A. insularis 中看到的一些染色体杂交信号，但在 A. magna 中没有看到，与六倍体燕麦物种共享，特别是与 A. byzantina 共享。这些诊断信号增加了这样一种观点，即现存的 A. insularis 或其直接祖先，是六倍体燕麦最密切相关的祖先。六倍体和 CCDD 四倍体的染色体杂交模式的相似性被认为是同源的。基于六倍体物种的 CCDD 物种的共同染色体命名法被提出。
