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首页> 外文期刊>Journal of genetics >Ascus dysgenesis in hybrid crosses of Neurospora and Sordaria (Sordariaceae)
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Ascus dysgenesis in hybrid crosses of Neurospora and Sordaria (Sordariaceae)

机译：Ascus在神经孢子孢子和Sordaria（Sordariaceae）的杂交杂交中

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摘要

When two lineages derived from a common ancestor become reproductively isolated (e.g. Neurospora crassa and N. tetrasperma), genes that have undergone mutation and adaptive evolution in one lineage can potentially become dysfunctional when transferred into the other, since other genes have undergone mutation and evolution in the second lineage, and the derived alleles were never 'tested' together before hybrid formation. Bateson (1909), Dobzhansky (1936), and Muller (1942) recognized that incompatibility between the derived alleles could potentially make the hybrid lethal, sterile, or display some other detriment. Alternatively, the detrimental effects seen in crosses with the hybrids may result from the silencing of ascus-development genes by meiotic silencing by unpaired DNA (MSUD). Aberrant transcripts from genes improperly paired in meiosis are processed into single-stranded MSUD-associated small interfering RNA (masiRNA), which is used to degrade complementary mRNA. Recently, backcrosses of N. crassa /N. tetrasperma hybrid translocation strains with wild-type N. tetrasperma were found to elicit novel ascus dysgenesis phenotypes. One was a transmission ratio distortion that apparently disfavoured the homokaryotic ascospores formed following alternate segregation. Another was the production of heterokaryotic ascospores in eight-spored asci. Lewis (1969) also had reported sighting rare eight-spored asci with heterokaryotic ascospores in interspecific crosses in Sordaria, a related genus. Ordinarily, in both Neurospora and Sordaria, the ascospores are partitioned at the eight-nucleus stage, and ascospores in eight-spored asci are initially uninucleate. Evidently, in hybrid crosses of the family Sordariaceae, ascospore partitioning can be delayed until after one or more mitoses following the postmeiotic mitosis.
机译：当来源于同一祖先的两个谱系在繁殖上分离时（例如粗糙脉孢菌和四精子纲），在一个谱系中经历了突变和适应性进化的基因在转移到另一个谱系时可能会出现功能失调，因为其他基因在第二个谱系中经历了突变和进化，在杂种形成之前，衍生的等位基因从未一起“测试”。Bateson（1909）、Dobzhansky（1936）和Muller（1942）认识到，衍生等位基因之间的不亲和性可能会使杂种致命、不育，或显示出其他一些危害。或者，在与杂种杂交中看到的有害影响可能是由于未配对DNA（MSUD）通过减数分裂沉默导致ascus发育基因沉默。来自减数分裂中不正确配对的基因的异常转录物被加工成单链MSUD相关小干扰RNA（masiRNA），用于降解互补mRNA。最近，人们发现粗糙N.crassa/N.tetrasperma杂交易位株与野生型N.tetrasperma的回交可引发新的ascus发育不良表型。一种是透射比畸变，这显然不利于交替分离后形成的同核子囊孢子。另一个是在八孢子asci中产生异核子囊孢子。Lewis（1969）还报告在Sordaria属（一个近缘属）的种间杂交中发现了罕见的八孢子asci，其中含有异核子囊孢子。通常，在脉孢菌和孢子囊菌中，子囊孢子在八核阶段被分开，而八孢子囊菌中的子囊孢子最初是单核的。显然，在Sordariaceae科的杂交组合中，子囊孢子的分配可以延迟到减数分裂后的一次或多次有丝分裂之后。

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