Functional Analysis of Forkhead Transcription Factor Fd59a in the Spermatogenesis of Drosophila melanogaster.

Simple Summary: Spermatogenesis, which is regulated by many different genes, is a conserved process across species to produce mature sperm for animal reproduction. Fox transcription factors can bind to DNA sequences in the promoters to regulate gene expression. FoxD subfamily members are mainly involved in metabolism and early organ development. In Drosophila melanogaster, FoxD subfamily member Fd59a may regulate the development of the nervous system and control the egg-laying behavior of females. However, the functions of insect FoxD members are still largely unknown. In this study, we investigated the role of Fd59a in the spermatogenesis of Drosophila. We found that mutations in Fd59a caused swelling of the apical region in the testis, resulting in fewer mature sperm in the seminal vesicle and significantly lower fertility of Fd59a mutant males compared to the control flies. We also found that the homeostasis of the testis stem cell niche in Fd59a mutant and RNAi flies was disrupted, causing increased apoptosis of sperm bundles. RNA sequencing and qRT-PCR results suggested that Fd59a can regulate the expression of genes related to reproductive process and cell death. Our collective results indicated that Fd59a plays a key role in Drosophila spermatogenesis, which will help to understand the role of FoxD members in insect spermatogenesis. Spermatogenesis is critical for insect reproduction and is regulated by many different genes. In this study, we found that Forkhead transcription factor Fd59a functions as a key factor in the spermatogenesis of Drosophila melanogaster. Fd59a contains a conversed Forkhead domain, and it is clustered to the FoxD subfamily with other FoxD members from some insect and vertebrate species. Mutations in Fd59a caused swelling in the apical region of the testis. More importantly, fewer mature sperm were present in the seminal vesicle of Fd59a mutant flies compared to the control flies, and the fertility of Fd59a2/2 mutant males was significantly lower than that of the control flies. Immunofluorescence staining showed that the homeostasis of the testis stem cell niche in Fd59a2/2 mutant and Fd59a RNAi flies was disrupted and the apoptosis of sperm bundles was increased. Furthermore, results from RNA sequencing and qRT-PCR suggested that Fd59a can regulate the expression of genes related to reproductive process and cell death. Taken together, our results indicated that Fd59a plays a key role in the spermatogenesis of Drosophila. [ABSTRACT FROM AUTHOR]