β2-tubulin regulates the development and migration of eupyrene sperm in Spodoptera frugiperda.

Spermatogenesis is the basis of sexual reproduction and is essential for the propagation of insect populations. Understanding the process of spermatogenesis and identifying key genes involved in sperm function can aid in developing pest genetic control methods. The testis-specific gene β2-tubulin (B2t) is crucial for spermatogenesis in insects possessing monomorphic spermatids. However, the role of B2t in lepidopteran dimorphic spermatogenesis remains unclear. In this study, we explored the effect of B2t in the development of eupyrene and apyrene sperm in the Spodoptera frugiperda, a major global pest. Knockout of B2t resulted in male sterility. B2t mutations lead to abnormal development of eupyrene sperm and the inability of eupyrene sperm to transfer from the testis to the double ejaculatory ducts. However, disruption of B2t did not affect apyrene spermatogenesis and migration. Interestingly, we found that first mating with B2t-null males inhibited sperm fertilization from a second wild-type male. Cage studies and mathematical modeling analyses suggested that releasing excessive B2t-null males suppressed female fertility. Our study provides insights into dimorphic spermatogenesis in lepidopteran pests and an efficient molecular target for pest genetic control techniques.