Marec F, Tothova A, Sahara K, Traut W
Department of Genetics, Institute of Entomology, Czech Academy of Sciences, Branisovská 31, CZ-370 05 Ceské Budejovice, Czech Republic.
Heredity (Edinb). 2001 Dec;87(Pt 6):659-71. doi: 10.1046/j.1365-2540.2001.00958.x.
The physical basis of non-Mendelian segregation of a sex-linked marker was studied in sex- chromosome mutant females of eight ASF ('abnormal segregating females') lines in the flour moth, Ephestia kuehniella. Electron microscopical analysis of microspread synaptonemal complexes revealed that in one line, the Z chromosome segment that contained the dz+ allele was translocated onto an autosome. The resulting quadrivalent visible in early female meiosis was 'corrected' into two bivalents in later stages. This explains autosomal inheritance of the sex chromosome marker in this strain. In the other seven ASF lines, the type of meiotic pairing of an additional fragment (Zdz+) of the Z chromosome was responsible for abnormal segregation of the marker gene. In several of these lines, Zdz+ contained a piece of the W chromosome in addition to the Z segment, as was confirmed by comparative genomic hybridization (CGH). Zdz+ formed three alternative pairing configurations with the original sex chromosomes: (i) a WZZdz+ trivalent, (ii) a WZ bivalent and a Zdz+ univalent or (iii) a ZZdz+ bivalent and a W univalent. In the most frequent WZZdz+ configuration, Zdz+ synapsed with Z and, consequently, segregated with W, simulating W linkage. This explains the predominant occurrence of the parental phenotypes in the progeny. Zdz+ univalents or W univalents, on the other hand, segregated randomly, resulting in both parental and nonparental phenotypes. In two of these lines, the Zdz+ was transmitted only to females. The results suggest that the W chromosome segment in Zdz+ of these lines contains a male-killing factor which makes it incompatible with male development. Our data provide direct evidence for the regular transmission of radiation-induced fragments from lepidopteran chromosomes through more than 50 generations. This is facilitated by the holokinetic nature of lepidopteran chromosomes. We conclude that Zdz+ fragments may persist as long as they possess active kinetochore elements.
在粉斑螟（Ephestia kuehniella）的8个ASF（“异常分离雌性”）品系的性染色体突变雌性个体中，研究了性连锁标记非孟德尔分离的物理基础。对微铺展联会复合体的电子显微镜分析表明，在一个品系中，包含dz +等位基因的Z染色体片段易位到了常染色体上。在雌性减数分裂早期可见的由此产生的四价体在后期“校正”为两个二价体。这解释了该品系中性染色体标记的常染色体遗传。在其他7个ASF品系中，Z染色体的一个额外片段（Zdz +）的减数分裂配对类型导致了标记基因的异常分离。通过比较基因组杂交（CGH）证实，在其中几个品系中，Zdz +除了Z片段外还包含一段W染色体。Zdz +与原始性染色体形成了三种不同的配对构型：（i）一个WZZdz +三价体，（ii）一个WZ二价体和一个Zdz +单价体，或（iii）一个ZZdz +二价体和一个W单价体。在最常见的WZZdz +构型中，Zdz +与Z联会，因此与W分离，模拟W连锁。这解释了后代中亲本表型的主要出现情况。另一方面，Zdz +单价体或W单价体随机分离，导致亲本表型和非亲本表型都出现。在其中两个品系中，Zdz +仅传递给雌性。结果表明，这些品系的Zdz +中的W染色体片段包含一个雄性致死因子，这使其与雄性发育不相容。我们的数据为辐射诱导的鳞翅目染色体片段通过50多代的正常传递提供了直接证据。鳞翅目染色体的全动粒性质促进了这一点。我们得出结论，只要Zdz +片段具有活跃的动粒元件，它们就可能持续存在。
