Mutation of Serine protease 1 Induces Male Sterility in Bombyx mori

Functional analysis of serine protease EfSP1 in Eocanthecona furcellata Wolff (Hemiptera: Pentatomidae)

BACKGROUND

Serine protease is an important digestive enzyme involved in many physiological and biochemical reactions, including digestion of insect food protein, blood coagulation, signal transduction, immune response, and hormone activation. The physiological functionality of salivary gland serine protease EfSP1 in the predatory natural enemy Eocanthecona furcellata is unknown. As a salivary gland protein, EfSP1 may have insecticidal activity against the prey Spodoptera frugiperda.

RESULTS

The expression of the EfSP1 gene was interfered with microinjection. After RNAi, the molting of the 5th instar nymphs of E. furcellata was blocked, and the survival rate and daily predation of male and female adults were reduced. The prokaryotic expression of EfSP1 protein was injected into the 4th instar larvae of S. frugiperda, causing difficulty in molting to death of the 4th instar larvae, and the dead larvae showed melanization, softening, and liquefaction. The development duration of the 4th instar larvae was prolonged, the survival rate was decreased, the pupal weight was decreased, the pupal period was prolonged, and the pupal eclosion rate was decreased. This inhibited the chitin and trehalose metabolism of S. frugiperda larvae, hemolymph melanization, and phenoloxidase activity, affecting the transcription of antimicrobial peptide genes.

CONCLUSION

These findings indicate that EfSP1 is involved in the growth, development, and predation of E. furcellata. As a salivary gland protein, EfSP1 also has insecticidal activity, affecting the growth and development, chitin metabolism, trehalose metabolism, and humoral immunity of S. frugiperda. These findings reveal the physiological function of EfSP1. © 2025 Society of Chemical Industry.

Dichotomous sperm in Lepidopteran insects: a biorational target for pest management

Lepidoptera are unusual in possessing two distinct kinds of sperm, regular nucleated (eupyrene) sperm and anucleate (apyrene) sperm ('parasperm'). Sperm of both types are transferred to the female and are required for male fertility. Apyrene sperm play 'helper' roles, assisting eupyrene sperm to gain access to unfertilized eggs and influencing the reproductive behavior of mated female moths. Sperm development and behavior are promising targets for environmentally safer, target-specific biorational control strategies in lepidopteran pest insects. Sperm dimorphism provides a wide window in which to manipulate sperm functionality and dynamics, thereby impairing the reproductive fitness of pest species. Opportunities to interfere with spermatozoa are available not only while sperm are still in the male (before copulation), but also in the female (after copulation, when sperm are still in the male-provided spermatophore, or during storage in the female's spermatheca). Biomolecular technologies like RNAi, miRNAs and CRISPR-Cas9 are promising strategies to achieve lepidopteran pest control by targeting genes directly or indirectly involved in dichotomous sperm production, function, or persistence.

Identification and expression profiling of serine protease-related genes in Tenebrio molitor

In insects, serine proteases and serine protease homologs (SPs/SPHs) are involved in a variety of physiological processes including digestion, development, and immunity. Here, we identified 112 SP and 88 SPH genes in the genome of the yellow mealworm, Tenebrio molitor. Based on the features of domain structure, they were divided into "S" group containing single Tryp-SPc or Tryp-SPHc domain, "C" group containing 1-4 CLIP domain (CLIPA-D) and "M" group containing the CBD, CUB, EGF, Fz, Gd, LDLa, PAN, SEA, SR, Sushi, and TSP domains, and have 115, 48, and 37 gene members, respectively. According to the active sites in the catalytic triad, the putative trypsin, chymotrypsin, or elastase-like enzyme specificity of the identified SPs/SPHs were predicted. Phylogenetic and genomic location analyses revealed that gene duplication exists in the large amount of SPs/SPHs. Gene expression profiling using RNA-seq data along with real time reverse transcription-polymerase chain reaction analysis showed that most SP/SPH genes display life stage specific expression patterns, indicating their important roles in development. Many SP/SPH genes are specifically or highly expressed in the gut, salivary gland, fat body, hemocyte, ovary, and testis, suggesting that they participate in digestion, immunity, and reproduction. The findings lay the foundation for further functional characterization of SPs/SPHs in T. molitor.

CRISPR/Cas9-mediated Serine protease 2 disruption induces male sterility in Spodoptera litura

Male fertility is essential for reproduction and population growth in animals. Many factors affect male fertility, such as courtship behavior, sperm quantity, and sperm motility, among others. Seminal Fluid Proteins (SFPs) are vital components of seminal fluid in the male ejaculate, which affect male fertility, sperm activation, and female ovulation. However, the knowledge of SFPs is insufficient; the function of many SFPs remains unknown, and most described functions were mainly characterized in Drosophila or other laboratory models. Here, we focus on the Serine protease 2 (Ser2) gene in the lepidopteran pest Spodoptera litura. The Ser2 gene was specifically expressed in male adults. Disruption of the Ser2 gene mediated by CRISPR/Cas9 induced male sterility but females remained fertile. PCR-based detection of the next-generation mutants showed that male sterility was stably inherited. The qRT-PCR analysis of SlSer2 mutants showed that motor protein family genes and structural protein family genes were down-regulated, while protein modification family genes were up-regulated, suggesting that SlSer2 may be involved in sperm movement and activity. These results demonstrate that Ser2 is an important component of SFPs in seminal fluid and was identified for a useful sterile gene for pest control that may lead to new control strategies for lepidopteran insect pests such as S. litura.