General sessions2E-10 Identification of the wasted gene essential for utilization of stored sperm in D.melanogaster

The male sterile mutant named wasted (wst) of D.melanogaster was isolated from a natural population in Katsunuma, Japan. It shows defects in three independent processes of utilization of stored sperm. (1) Entry rate into eggs of the wst sperm decreases a half of the initial level in one day after copulation. (2) The wst sperm in seminal receptacles are lost within two days after copulation. (3) The inseminating wst sperm fail to form the male pronucleus. To identify the wst gene, we analyzed nucleotide sequences of putative exons of 17 genes located in a 170 kb region to which wst was mapped. We found a four-nucleotides deletion that introduced a premature stop codon in a gene. The wild-type allele of the gene rescued the male sterility due to wst mutation, indicating that three defects of the wst sperm are caused by a single gene mutation. Sequencing of cDNAs revealed a potential ORF of 1,503 amino acids that shows no homology to known conserved domains. The orthologs were found only in species of the genus Drosophila, suggesting that the wst gene had occurred after the divergence of the genus and had acquired novel Drosophila-specific functions in the reproductive system.