Abstract
Clip-domain serine proteases (CLIPs) play crucial roles in insect development and innate immunity. In this study, we identified a CLIP gene (designated LsCLIP3) from the cigarette beetle Lasioderma serricorne. LsCLIP3 contains a 1,773-bp open reading frame (ORF) encoding a 390-amino-acid protein and shows a conserved clip domain and a trypsin-like serine protease domain. Phylogenetic analysis indicated that LsCLIP3 was orthologous to the CLIP-B subfamily. LsCLIP3 was prominently expressed in larva, pupa, and early adult stages. In larval tissues, it was highly expressed in the integument and fat body. The expression of LsCLIP3 was induced by 20-hydroxyecdysone. A similar induction was also found by peptidoglycans from Escherichia coli and Staphylococcus aureus. RNA interference (RNAi)-mediated silencing of LsCLIP3 disrupted larval–pupal molting and specifically reduced the expression of genes in 20-hydroxyecdysone synthesis and signaling pathway. The chitin amounts of LsCLIP3 RNAi larvae were greatly decreased, and expressions of six chitin metabolic-related genes were significantly reduced. Knockdown of LsCLIP3 increased larval sensitivity to Gram-negative and Gram-positive bacteria. There was significantly decreased expression of four antimicrobial peptide (AMP) genes. The results suggest that LsCLIP3 is an important component of the larva to pupa molt and for the immunity of L. serricorne.
Highlights
Serine proteases (SPs) comprise a large family of proteolytic enzymes
The full open reading frame (ORF) of the Clip-domain serine proteases (CLIPs) sequence was confirmed by reverse transcription PCR
A signal peptide with 20 amino acids were found at the N-terminal ends of LsCLIP3
Summary
Serine proteases (SPs) comprise a large family of proteolytic enzymes. They are characterized by a conserved His–Asp–Ser catalytic triad active site domain. SPs participate in physiological processes such as digestion, immune responses, fertilization, and embryonic development (Lu et al, 2014; Veillard et al, 2016). SP homologs (SPHs) are a family of enzymes with a similar amino acid sequence as SPs but lacking the amidase activity required for the substitution of catalytic residues (Ross et al, 2003). SPs and SPHs constitute a large family of proteases in insects, with 50−300 genes in genomes (Veillard et al, 2016).
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