Bugs, Flies, and Spuds: A Story of Co-evolution

n° 384 - May-June 2000


Infectious diseases continue to pose a serious public health threat worldwide. Scientists and doctors are involved in an intensive effort to understand the molecular features of host-pathogen relationships and are always on the look-out for ideal model systems to study. A group of researchers at the CNRS Centre de Génétique Moléculaire (CGM)* have identified an insect pathogen which may offer important insights for human disease.

The CGM group studies infections in the fruitfly Drosophila. Drosophila offers several attractive features, such as a relatively simple immune system and powerful experimental genetics. In response to microbial infections, Drosophila produce a battery of potent anti-bacterial and anti-fungal peptides. However, no natural bacterial pathogen of Drosophila had been identified previously that induces these peptides. After an extensive search the researchers identified a bacterial strain, Erwinia carotovora, which was capable of infecting Drosophila larvae and activating anti-bacterial peptide genes1. Erwinia carotovora is a phytopathogenic bacteria which causes blackleg disease in potatoes and uses flies as a vector to propagate between plants. The Erwinia-Drosophila infection is highly specific and the bacteria appear to have evolved to exploit the fly host. Furthermore, Drosophila may benefit from the fruit rot produced by the phytopathogenic bacteria. Hence, this complex co-evolution of flies and bugs offers an attractive system for subsequent identification of the genes regulating key features of host-pathogen interactions.

* Centre de Génétique Moléculaire, F-91198 Gif-sur-Yvette, France.

1 Basset A., Khush R. S., Braun A., Gardan L., Boccard F., Hoffmann J. A., Lemaitre B. The phytopathogenic bacteria Erwinia carotovora infects Drosophila and activates an immune response. Proc. Natl. Acad. Sci. USA (2000) 97: 3376-3381.


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