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

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.

The expression of the EfSP1 gene was interfered with microinjection. After RNAi, the molting of the 5^th 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 4^th instar larvae of S. frugiperda, causing difficulty in molting to death of the 4^th instar larvae, and the dead larvae showed melanization, softening, and liquefaction. The development duration of the 4^th 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.

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.