Role of serine protease inhibitors in insect‐host‐pathogen interactions

Abstract Serine protease inhibitors (serpins), evolutionary old, structurally conserved molecules, are a superfamily of proteins found in almost all living organisms. Serpins are relatively large, typically 350–500 amino acids in length, with three β‐sheets and seven to nine α‐helices folding into a conserved tertiary structure with a reactive center loop. Serpins perform various physiological functions in insects, including development, digestion, host‐pathogen interactions, and innate immune response. In insects, the innate immune system is characterized as the first and major defense system against the invasion of microorganisms. Serine protease cascades play a critical role in the initiation of innate immune responses, such as melanization and the production of antimicrobial peptides, and are strictly and precisely regulated by serpins. Herein, we provide a microreview on the role of serpins in the insect‐host‐pathogen interactions, emphasizing their role in immune responses, particularly in diamondback moth ( Plutella xylostella ), highlighting the important discoveries and also the gaps that remain to be explored in future studies.