Midgut immune responses induced by bacterial infection in the silkworm, Bombyx mori

• Published in: Journal of Zhejiang University. B. Science 2015-10, Vol.16 (10), p.875-882
• Main Authors: Zhang, Lei, Wang, Yan-wen, Lu, Zhi-qiang
• Format: Article
• Language: English
• Subjects: Animals; Antiinfectives and antibacterials; Antimicrobial peptides; Bacillus; Bacillus bombysepticus; Bacteria; Bacterial infections; Bacterial Infections - immunology; Biomedical and Life Sciences; Biomedicine; Bombyx - immunology; Bombyx - microbiology; Bombyx mori; Catalase; China; Cytokines - immunology; Epithelial cells; Gastrointestinal tract; Gene expression; gene expression regulation; genes; hosts; Hydrogen peroxide; Immune response; Immune system; Immunity, Innate - immunology; inducible nitric oxide synthase; Infections; Intestine; Intestines - immunology; Intestines - microbiology; larvae; messenger RNA; Microorganisms; Midgut; NAD(P)H oxidase (H2O2-forming); Nitric oxide; Nitric-oxide synthase; Oxidase; Pathogenicity; Pathogens; Peptides; Polymerase chain reaction; Pseudomonas; Pseudomonas aeruginosa; quantitative polymerase chain reaction; Reactive oxygen species; Reactive Oxygen Species - immunology; Real time; Silkworms; Survival; Transcription; transcription (genetics)
• ISSN: 1673-1581; 1862-1783
• DOI: 10.1631/jzus.B1500060

Insect gut epithelial cells produce reactive oxygen species (ROS) and antimicrobial peptides (AMPs) to protect hosts from pathogenic microorganisms. In this study, we evaluate the pathogenicity of Pseudomonas aeruginosa and Bacillus bombysepticus in the silkworm, Bombyx mori . Survival curves show that B. bombysepticus is deadly when larval silkworms are infected orally. Bacterial infection caused intestinal hydrogen peroxide (H 2 O 2 ) and nitric oxide (NO) levels to increase significantly by 8 and 16 h post-infection (hpi), respectively. Real-time quantitative polymerase chain reaction (qPCR) analysis shows that the transcription levels of dual oxidase ( Duox ) and catalase ( CAT ) are highly up-regulated by P. aeruginosa infection at 8 hpi. P. aeruginosa infection induced nitric oxide synthase 2 ( NOS2 ) expression at 16 hpi, which contributes to the generation of NO. mRNA levels of AMP genes, specifically Glovorin 2 and Glovorin 3, which obviously increase during the early infection stage. These results indicate that invading bacteria elevate intestinal ROS and NO levels and induce AMP gene transcription, which contributes to intestinal immune defense.