Reproductive Genetics of neurospora tetrasperma

四子精神经孢子菌的生殖遗传学

• 批准号: 9713015
• 负责人: David Jacobson
• 金额: $ 14.13万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-05-15 至 2001-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9713015&HistoricalAwards=false
• 关键词: Reproductive; Genetics; neurospora; tetrasperma

Jacobson 97-13015 Unlike N. crassa, which is heterothallic and produces haploid ascospores of two separate mating types, N. tetrasperma is self fertile as a consequence of each ascopore receiving one nucleus of each mating type. This reproductive system has been termed pseudohomothallism, because occasional single mating-type spores are self sterile and heterothallic, suggesting the potential for outcrossing in nature. At one level, the mechanism of pseudohomothallism in N. tetrasperma appears quite simple. An overlap of spindles at the second meiotic division, together with subsequent programmed nuclear movements, leads to four heterokaryotic ascospores per ascus, instead of the eight typical of N. crassa and other truly heterothallic species. Despite this deceptively simple mechanism for creating self-fertile ascospores, it is now clear that pseudohomothallism in N. tetrasperma has important and complex implications. One recent study revealed that laboratory outcrossing with geographically diverse strains of N. tetrasperma results in high levels of sexual dysfunction. Another demonstrated that recombination between N. tetrasperma mating-type chromosomes is suppressed relative to that observed for truly heterothallic species, such as N. crassa; and it demonstrated that the mating-type chromosomes and autosomes of N. tetrasperma reflect very different evolutionary histories. Paradoxically, suppressed recombination on the mating-type chromosome, coupled with the unique sexual developmental pathway of N. tetrasperma, has produced wild-type strains with high levels of heteroallelism on the mating-type chromosome, but with virtually complete homoallelism for sequences on autosomes. The results of these two studies appear to be very much interrelated. For example, one aspect of sexual dysfunction seems to involve protoplasmic incompatibility brought about by heteroallelism at certain loci. The high levels of homoallelism observed for autosomal sequences in wild type strains may reflect an avoidance of this incompatibility. This research will investigate (1) the genetic bases of sexual dysfunction and (2) the mechanism and biological significance of suppressed recombination on the mating-type chromosome. Our study focuses on several fundamental aspects of developmental and life-cycle biology, and it therefore has broad implications for reproductive genetics in higher organisms. This study will go far toward developing N. tetrasperma as an experimental organism for future genetic studies.

Jacobson 97-13015 与粗糙猪笼草不同，粗糙猪笼草是异质并产生两种不同交配类型的单倍体子囊孢子，四子猪笼草是自体受精的，因为每个子囊孔接受每种交配类型的一个核。 这种生殖系统被称为假同种异体，因为偶尔的单一交配型孢子是自交不育和异宗交配的，这表明自然界中存在异交的潜力。 在某种程度上，四子猪笼草的拟同位素机制似乎相当简单。 第二次减数分裂时纺锤体的重叠，以及随后的程序化核运动，导致每个子囊有四个异核子囊孢子，而不是粗糙猪笼草和其他真正异宗合物种的典型的八个。 尽管这种产生自体受精子囊孢子的机制看似简单，但现在很清楚，四子孢子虫中的假同胚性具有重要而复杂的含义。 最近的一项研究表明，实验室与不同地域的四子猪笼草菌株进行异型杂交会导致严重的性功能障碍。 另一项研究表明，相对于真正的异种植物物种（例如粗糙猪笼草）观察到的重组，四子猪笼草交配型染色体之间的重组受到抑制。 它证明了四子猪笼草的交配型染色体和常染色体反映了截然不同的进化历史。 矛盾的是，交配型染色体上的重组受到抑制，加上四子猪笼草独特的性发育途径，产生了在交配型染色体上具有高水平异等位性的野生型菌株，但常染色体上的序列几乎具有完全的同源等位性。 这两项研究的结果似乎非常相关。 例如，性功能障碍的一方面似乎涉及由某些位点的异等位性引起的原生质不相容性。 在野生型菌株中观察到的常染色体序列的高水平同源性可能反映了这种不相容性的避免。 本研究将研究（1）性功能障碍的遗传基础和（2）交配型染色体上重组受抑制的机制和生物学意义。 我们的研究重点关注发育和生命周期生物学的几个基本方面，因此对高等生物的生殖遗传学具有广泛的影响。 这项研究将有助于将四子猪笼草开发为未来遗传学研究的实验生物。