How do hosts regulate internal symbionts to prevent them from taking over their bodies without compromising the advantages of the relationship? Login et al. explored the balance between host innate immune responses and bacterial replication of an endosymbiont in weevils, an important beetle pest of wheat. A single peptide, coleoptericin-A (ColA), synthesized by the beetle constrained the bacteria within bacteriocytes and blocked bacterial replication. When the weevil’s ColA expression was silenced, the bacteria were able to replicate normally, escape the bacteriocyte, and spread throughout the insect.
F. H. Login, S. Balmand, A. Vallier, C. Vincent-Monégat, A. Vigneron, M. Weiss-Gayet, D. Rochat, A. Heddi, Antimicrobial peptides keep insect endosymbionts under control. Science 334, 362–365 (2011). [Abstract] [Full Text]