Characterization of two Segregation distorter revertants: evidence that the tandem duplication is necessary for Sd activity in Drosophila melanogaster.
Characterization of two Segregation distorter revertants: evidence that the tandem duplication is necessary for Sd activity in Drosophila melanogaster.
复制标题
两种分离扭曲回复突变体的表征：串联重复对于黑腹果蝇中的 Sd 活性是必要的证据。
DOI：
10.1093/genetics/136.1.209
复制
发表时间：
1994
期刊：
影响因子：
3.3
通讯作者：
Wu,CI
中科院分区：
文献类型：
--
作者：
Palopoli,MF;Doshi,P;Wu,CI
分离偏差(SD)是果蝇减数分裂驱动的一种自然系统。具有SD第二染色体和正常同源(SD+)杂合子的男性主要传递携带SD的精子。为了实现这一点，分离扭曲(SD)基因座导致接受SD+染色体的精子细胞功能障碍。最近，P.A.Power和B.Ganetzky分离了跨越已知包含SD基因的DNA区域的重叠DNA克隆，并发现了一个5kb的串联重复，该重复存在于所有被检查的SD染色体上，但显然在野生型染色体中不存在。在这里，我们报告了来自澳大利亚SD染色体(SD-ARM28)的两个自发回复突变体的分子分析。这两个逆转株都失去了5kb的串联复制和扭曲传递的能力；然而，关键的观察是，它们在侧翼区域(近端和远端)保留了原始SD-Arm28所特有的DNA单倍型。我们提出串联重复序列之间不相等的姐妹染色单体交换是在保留侧翼标记的同时丢失重复序列的唯一可信的解释。这提供了直接证据，表明串联复制对于SD表型确实是必要的。此外，我们还检测了邻近拓扑异构酶2基因的睾丸特异性RNA和蛋白质水平。两者都没有显示出SD和SD+菌株之间的一致差异。我们还使用串联复制本身作为探针来测量睾丸特异的RNA水平。我们的结果表明，SD株睾丸中复制区域的一个或几个2.0-2.3kb的转录本有很强的上调。
Segregation Distorter (SD) is a naturally occurring system of meiotic drive in Drosophila melanogaster. Males heterozygous for an SD second chromosome and a normal homolog (SD+) transmit predominantly SD-bearing sperm. To accomplish this, the Segregation distorter (Sd) locus induces the dysfunction of those spermatids that receive the SD+ chromosome. Recently, P. A. Powers and B. Ganetzky isolated overlapping DNA clones spanning the region of DNA known to contain the Sd gene and identified a 5-kb tandem duplication that is present on all SD chromosomes examined, but is apparently absent from wild-type chromosomes. Here we report a molecular analysis of two spontaneous revertants from an Australian SD chromosome (SD-Arm28). Both of these revertants have lost the 5-kb tandem duplication along with the ability to distort transmission; the critical observation, however, is that they retain the DNA haplotype in the flanking regions (both proximally and distally) that is characteristic of the original SD-Arm28. We propose unequal sister chromatid exchange between the tandem repeats as the only plausible explanation for loss of a repeat while retaining flanking markers. This provides direct evidence that the tandem duplication is indeed necessary for the Sd phenotype. Further, we examined testes-specific levels of both RNA and protein for the nearby Topoisomerase 2 gene. Neither revealed a consistent difference between SD and SD+ strains. We also measured testes-specific levels of RNA using the tandem duplication itself as probe. Our results suggest that there is strong up-regulation of one or several 2.0-2.3-kb transcripts from the duplicated region in the testes of an SD strain.(ABSTRACT TRUNCATED AT 250 WORDS)