3D-09 Identification of a fertilization gene ms(2)n55 in Drosophila melanogaster

ms(2)n55 is a male sterile mutation isolated from a natural population. n55 sperm are motile, transferred to the female by copulation, but unable to fertilize the eggs. Although the n55 sperm are stored normally in female sperm storage organs immediately after copulation, most of the stored sperm are exhausted within 24 hours. The sperm are released coordinately with ovulation but only 44% eggs are inseminated, indicating that the insemination ability of the n55 sperm is significantly reduced. Furthermore, the sperm enter into the eggs, do not undergo nuclear decondensation and fail to initiate embryogenesis. In order to analyze the mechanism of each process of fertilization, the genes resulted in the three phenotypes should be separated and identified. Here we report that two genes, n55-s involved in sperm storage and entering into eggs and n55-d necessary for nuclear decondensation, were separated by recoinbination. The n55-s gene was known to locate in the chromosomal region of 140kb interval in 33F2;34A1. By examining breakpoints of deletions made by P element imprecise excision, we have currently narrowed down to three genes.