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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Diploid apomicts of the Boechera holboellii complex display large-scale chromosome substitutions and aberrant chromosomes
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Diploid apomicts of the Boechera holboellii complex display large-scale chromosome substitutions and aberrant chromosomes

机译：Boechera holboellii复合体的二倍体无融合生殖显示大规模染色体置换和异常染色体

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摘要

We conducted a cytogenetic study of sexual lines of Boechera stricta and Boechera holboellii (2n = 14) and seven diploid apomic-tic accessions of their interspecific hybrid Boechera divaricarpa and B. holboellii (2n = 14 or 15). By studying chromosome morphology, rDNA repeats, genome painting, male meiosis, pollen morphology, and flow-cytometry seed screens, we revealed an unexpected plethora of chromosome forms, pairing behavior, and hybrid composition in all apomictic lines. Genome painting demonstrated that the apomicts are alloploid with variable numbers of B. stricta and B. holboellii-like chromosomes. We assume that large-scale homeologous chromosome substitutions took place in the apomictic hybrids that resulted from recurrent diploid-polyploid transitions through restitutional meiosis and polyploidy-diploid transitions through reductional meiosis. A second peculiarity was the presence of a largely heterochromatic chromosome (Het) in all apomictic accessions (2n = 14 and 15) and an additional smaller chromosome (Del) in the aneuploids (2n = 15). Both chromosomes share repetitive pericentromere repeats with those from the sexual B. stricta, suggesting that they originated from this species. Pairing and behavior at meiosis I of the Het share features with both Y and B chromosomes and suggest that the Del arose from a transloca-tion event or homeologous recombination between a B. holboellii (or related taxon) and a B. stricta chromosome. Based on its presence exclusively in apomictic accessions, we propose that the Het chromosome plays a role in the genetic control of apomixis.
机译：我们进行了严格的Boechera严格和Boechera holboellii（2n = 14）和其种间杂种Boechera divaricarpa和B. holboellii（2n = 14或15）的七个二倍体无融合生殖细胞质的细胞遗传学研究。通过研究染色体形态，rDNA重复，基因组绘画，雄性减数分裂，花粉形态和流式细胞术种子筛选，我们揭示了所有无融合生殖系中出乎意料的大量染色体形式，配对行为和杂种组成。基因组绘画表明，该融合体是同种异体，具有数目不等的B. stricta和B. holboellii染色体。我们假设大规模的同源染色体置换发生在无融合生殖杂种中，这是通过重组减数分裂的反复二倍体-多倍体转变和还原性减数分裂产生的多倍体-二倍体转变所致。第二个特点是在所有无融合生殖种系中均存在一个很大的异色染色体（Het）（2n = 14和15），在非整倍体中还存在一个较小的染色体（Del）（2n = 15）。两条染色体都与有性双歧杆菌共享重复的着丝粒重复，表明它们起源于该物种。 Het减数分裂I的配对和行为与Y和B染色体共享特征，并表明Del起源于霍乱芽孢杆菌（或相关分类群）和严格芽孢杆菌染色体之间的易位事件或同源重组。基于其仅存在于无融合生殖种质中，我们建议Het染色体在无融合生殖的遗传控制中起作用。

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