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Insect immunity. Constitutive expression of a cysteine-rich antifungal and a linear antibacterial peptide in a

M Lamberty1, D Zachary, R Lanot

  • 1Institut de Biologie Moléculaire et Cellulaire, Unité Propre de Recherche 9022, CNRS, "Réponse Immunitaire et Développement chez les Insectes," 15 rue René Descartes, 67084 Strasbourg Cedex, France.

The Journal of Biological Chemistry
|October 29, 2000
PubMed

Insights

Two new antimicrobial peptides, termicin and spinigerin, were discovered in the termite Pseudacanthotermes spiniger. These peptides exhibit antifungal and antibacterial properties and are constitutively present, unlike induced peptides in other insects.

Area of Science:

  • * Insect immunology
  • * Antimicrobial peptide research
  • * Termite biology

Background:

  • * Insects possess innate immune systems with antimicrobial peptides (AMPs) to combat pathogens.
  • * AMPs are typically induced upon infection in many insect species, particularly those with complete metamorphosis.
  • * The immune strategies of lower insects like termites (Isoptera) remain less explored.

Purpose of the Study:

  • * To isolate and characterize novel antimicrobial peptides from the fungus-growing termite Pseudacanthotermes spiniger.
  • * To investigate the structural features and biological activities of these newly identified peptides.
  • * To understand the expression and localization of these peptides in unchallenged termites.

Main Methods:

  • * Isolation and purification of peptides from P. spiniger.
  • * Amino acid sequencing and structural analysis of the isolated peptides.
  • * Antimicrobial activity assays against various bacterial and fungal species.
  • * Immunohistochemical localization of peptides within termite tissues.

Main Results:

  • * Isolation of two novel antimicrobial peptides: termicin (36 amino acids, antifungal) and spinigerin (25 amino acids, antibacterial and antifungal).
  • * Termicin contains six cysteines in a defensin-like array but is C-terminally amidated; spinigerin lacks cysteines.
  • * Neither peptide shows significant sequence similarity to known antimicrobial peptides.
  • * Termicin and spinigerin are constitutively expressed in hemocyte granules and salivary glands of unchallenged termites.

Conclusions:

  • * Termicin and spinigerin represent novel classes of antimicrobial peptides with unique structural and functional characteristics.
  • * Their constitutive presence in specific tissues suggests a role in continuous defense mechanisms in P. spiniger.
  • * This contrasts with the inducible immune responses observed in many other insect groups, highlighting potential evolutionary divergence in innate immunity.

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