Zickler D, de Lares L, Moreau P J, Leblon G
Chromosoma. 1985;92(1):37-47. doi: 10.1007/BF00327243.
The recessive meiotic mutant spo44 of Sordaria macrospora, with 90% ascospore abortion, exhibits striking effects on recombination (67% decrease), irregular segregation of the almost unpaired homologues, and a decrease in chiasma frequency in the few cases where bivalents are formed. Three-dimensional reconstructions of ten prophase nuclei indicate that pairing, as judged by the absence of fully formed synaptonemal complexes (SC), is not achieved although lateral elements (LE) assemble. The pairing failure is attributable to defects in the alignment of homologous chromosomes. The leptotene alignment seen in the wild type before SC formation was not observed in the spo44 nuclei. Dense material, considered to be precursor of SC central elements, was found scattered among the LE in two nuclei. The behaviour of spo44 substantiates the hypothesis that chromosome matching and SC formation are separable events. - The total length of the LE in the mutant is the same as in the wild type, but due to variable numbers and length of the individual LE, homologues cannot be lined up. Light microscopic observations indicate that the irregular length and number of LE is due to extensive chromosome breakage. The wild-type function corresponding to spo44 is required for both LE integrity and chromosome matching. Reconstructions of heterozygous nuclei reveal the presence of a supernumerary nucleolar organizer in one arm of chromosome 7. It is suggested that rDNA has been inserted into a gene whose function is involved in pairing or into a controlling sequence that interacts with the pairing process.
大孢粪壳菌的隐性减数分裂突变体spo44，其90%的子囊孢子败育，对重组表现出显著影响（减少67%），几乎未配对的同源染色体出现不规则分离，并且在少数形成二价体的情况下交叉频率降低。对十个前期细胞核的三维重建表明，尽管侧生元件（LE）组装，但从完全形成的联会复合体（SC）缺失判断，配对并未实现。配对失败归因于同源染色体排列缺陷。在spo44细胞核中未观察到野生型在SC形成前的细线期排列。在两个细胞核中发现致密物质（被认为是SC中央元件的前体）散布在LE之间。spo44的行为证实了染色体匹配和SC形成是可分离事件的假设。 - 突变体中LE的总长度与野生型相同，但由于单个LE的数量和长度可变，同源染色体无法排列整齐。光学显微镜观察表明，LE长度和数量的不规则是由于广泛的染色体断裂。spo44对应的野生型功能对于LE完整性和染色体匹配都是必需的。杂合细胞核的重建揭示了7号染色体一条臂上存在一个额外的核仁组织区。有人提出rDNA已插入到一个其功能涉及配对的基因中或插入到一个与配对过程相互作用的控制序列中。
