ζTrypsin is required for spermatid elongation and individualization in Drosophila spermatogenesis

During Drosophila spermatogenesis, mitochondria undergo elongation along the entire length of the spermatid tail, thereby establishing a structural framework that facilitates microtubule reorganization and the synchronized individualization of spermatids. This process ultimately culminates in the production of functional, mature sperm. Despite this understanding, the regulatory mechanisms governing elongation and individualization remain largely unexplored. The gene ζTrypsin encodes a member of the serine protease enzyme family. However, its molecular function remains to be elucidated. In this study, we elucidated the critical role of ζTrypsin in the process of spermatid individualization. In ζTrypsin knockdown testes, spermatid individualization complexes with F-actin cones were either entirely absent or disrupted, leading to an absence of mature sperm in the seminal vesicle and resulting in reduced male fertility. The most significant effects included reduced tubulin polyglycylation and disrupted mitochondrial function. Transcriptome analysis identified 1878 differentially expressed genes, with 814 genes upregulated and 1064 genes downregulated. These findings suggest that ζTrypsin is essential for spermatid maturation by influencing mitochondrial morphogenesis.