The genders of Drosophila melanogaster vary in their sensitivities to microbial pathogens. While many of the immunity-related genes are located on the X chromosome, the polymorphisms within the Y chromosome were also shown to affect the immunity of flies. In this study, we investigated the necessity of individual genes on the Y chromosome (Y-genes) for male sensitivity to microbes. We identified several Y-genes whose genetic inactivation either increases or decreases the sensitivity of males to gastrointestinal infections with fungal Saccharomyces cerevisiae and bacterial Serratia liquefaciens. Specifically, the loss of function mutations in fly kl-5 and Ppr-Y Y-genes lead to increased and decreased sensitivity of males to fungal challenge, respectively, compared to female sensitivity. In contrast, mutations in Drosophila Pp1-Y1, kl-5, kl-3, Ppr-Y, CCY, and FDY Y-genes lead to increased sensitivity of males to bacterial infection, compared to females. Moreover, while these Y-genes are necessary, the Y chromosome is not sufficient for the sensitivity of males to microbes, since the sensitivity of XXY females to fungal and bacterial challenges was not different from the sensitivity of wild-type female flies, compared to males. This study assigns a new immunity-related function to numerous Y-genes in D. melanogaster.
Keywords: Drosophila melanogaster; Saccharomyces cerevisiae; Serratia liquefaciens; Y chromosome; microbial infections; sexual dimorphism.