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Differential sensitivity to infections and antimicrobial peptide-mediated immune response in four silkworm strains
Ottavia Romoli1, Alessio Saviane2, Andrea Bozzato1
1Department of Biology, University of Padova, Padova, Italy.
Abstract:
The domesticated silkworm Bombyx mori has an innate immune system, whose main effectors are the antimicrobial peptides (AMPs). Silkworm strains are commonly grouped into four geographical types (Japanese, Chinese, European and Tropical) and are generally characterised by a variable susceptibility to infections. To clarify the genetic and molecular mechanisms on which the different responses to infections are based, we exposed one silkworm strain for each geographical area to oral infections with the silkworm pathogens Enterococcus mundtii or Serratia marcescens. We detected a differential susceptibility to both bacteria, with the European strain displaying the lowest sensitivity to E. mundtii and the Indian one to S. marcescens. We found that all the strains were able to activate the AMP response against E. mundtii. However, the highest tolerance of the European strain appeared to be related to the specific composition of its AMP cocktail, containing more effective variants such as a peculiar Cecropin B6 isoform. The resistance of the Indian strain to S. marcescens seemed to be associated with its prompt capability to activate the systemic transcription of AMPs. These data suggest that B. mori strains with distinct genetic backgrounds employ different strategies to counteract bacterial infections, whose efficacy appears to be pathogen-dependent.
Insights
Silkworm (Bombyx mori) strains show varied resistance to bacterial infections. Their immune responses, particularly antimicrobial peptides (AMPs), differ based on genetic background and pathogen type.
Area of Science:
- * Insect immunology
- * Genomics and molecular biology
Background:
- * The domesticated silkworm, Bombyx mori, possesses an innate immune system primarily mediated by antimicrobial peptides (AMPs).
- * Distinct geographical strains of B. mori exhibit variable susceptibility to infections, suggesting underlying genetic and molecular differences in their immune responses.
Purpose of the Study:
- * To investigate the genetic and molecular mechanisms behind differential immune responses in Bombyx mori strains.
- * To understand how different silkworm geographical types respond to specific bacterial pathogens.
Main Methods:
- * Oral infection of four distinct Bombyx mori geographical strains (Japanese, Chinese, European, Tropical) with Enterococcus mundtii and Serratia marcescens.
- * Assessment of differential susceptibility and analysis of antimicrobial peptide (AMP) activation and transcription.
Main Results:
- * European and Indian silkworm strains showed differential susceptibility, with European strains being less sensitive to E. mundtii and Indian strains to S. marcescens.
- * All strains activated AMP responses against E. mundtii, but the European strain's higher tolerance was linked to a unique AMP composition (Cecropin B6 isoform).
- * The Indian strain's resistance to S. marcescens correlated with rapid systemic AMP gene transcription.
Conclusions:
- * Bombyx mori strains with different genetic backgrounds utilize distinct strategies to combat bacterial infections.
- * The effectiveness of these immune strategies is dependent on the specific pathogen encountered.
