EFFECT OF OTU MUTATIONS ON MALE-FERTILITY AND SPERMATOGENESIS IN DROSOPHILA-MELANOGASTER

The 17-ethyl-methyl-sulphonate (EMS) induced female sterile alleles of the ovarian tumour (otu) locus show a wide spectrum of phenotypes and affect various processes of Drosophila oogenesis. These phenotypes ha ve been previously studied in detail, but the exact molecular function of the otu locus in the different processes of oogenesis is only poor ly known. To date, no effect of otu mutations have been reported in th e males. However, separate species of otu mRNAs are expressed in the t estes and the thorax of the adult male, but their role is not known. I n this study we analysed the effects of EMS-induced otu mutations on m ale fertility. We observed that the proportion of totally sterile male s is significantly higher in most of the tested otu strains as compare d to the wild type. There was a strong correlation between male steril ity and severity of impairment in the female phenotype. Spermatogenesi s of these semi-sterile strains was analysed by phase contrast microsc opy, Hoechst 33258 and Feulgen stain, and by in situ hybridisation wit h testis-specific probes. No changes which could account for the induc tion of sterility were recorded and normal amounts of motile sperm wer e observed in all strains. Sterility turned out to be a consequence of a failure in mating behaviour. The wild type females refused to react to the courtship attempts of the mutant males. We propose two alterna tive explanations for this. Either the otu locus may play some importa nt role in male somatic tissue, or some germ line function is necessar y for correct mating behaviour.