Identification of cytoplasmic factor inhibiting the Y-sperm maturation and cytogenetical analysis of spermatogenesis.

从野生种群中分离出了一种表现出极端性别比的菌株。最初有报道称，该菌株携带一种细胞质因子，这种因子通过母体传播，在携带细胞质的雄性体内导致性别比扭曲。因此，我们研究了抗生素、衰老、线粒体DNA、细胞质RNA和细胞质移植对性别比扭曲的影响，以确定细胞质因素，但不能支持最初的描述。然而，我们在拟果蝇品系的X染色体上发现了性别比突变。该基因命名为父系无子(PSL)，位于图谱距离约30处，在果蝇属物种复合体中尚未发现。细胞遗传学研究表明，PSL雄性在减数分裂时染色体桥的频率很高，尤其是在第二次分裂时，导致多核精母细胞和精子细胞。几乎每个异常精子细胞在胞质分裂部位都有大量荧光阳性染色质。在精子成熟过程中，异常的精子细胞大多从精子囊中被丢弃。只有主要由X精子组成的正常精子才会成熟。

A strain which exhibits an extreme sex ratio has been isolated from a wild population. The strain was originally reported to carry an cytoplasmic factor which is transmitted materhally and causes sex ratio distortion through in the males bearing the cytoplasm. We therefore examined the effect of an antibiotic, aging, mitochondrial DNA, cytoplasmic RNA and transplantation of the cytoplasm on the sex ratio distortion in order to identify the cytoplasmic factor, but could not support the original description. However we have found a sex ratio mutation on the X chromosome of the Drosophila simulans strain. The gene named paternal sonless (psl) is located at about 30 in map distance and has not been known in any species belonging to the Drosophila melanogaster species complex. Cytogenetical studies revealed as follows; The psl males show a high frequency of chromosome bridges at meiosis, especially at the second division, which resulting in multi-nuclear spermatocytes and spermatids. Almost every abnormal spermatid has a mass of fluorescent positive chromatin at the site of cytokinesis. The abnormal spermatids are mostly discarded from sperm cysts in the maturation process. Only normal sperms, which are consisted of largely X-sperms, get matured.