1. Type III secretion systems and the evolution of mutualistic endosymbiosis
- Author
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Lawrence, T.E., Plague, Gordon R., Wang, Ben, Ochman, Howard, and Moran, Nancy A.
- Subjects
Molecular biology -- Research ,Host-bacteria relationships -- Research ,Endosymbiosis -- Genetic aspects ,Cladistic analysis -- Usage ,Parasites -- Environmental aspects ,Insects -- Environmental aspects ,Evolution -- Research ,Secretion -- Regulation ,Science and technology - Abstract
The view that parasites can develop cooperative symbiotic relationships with their hosts is both appealing and widely held; however, there is no molecular genetic evidence of such a transition. Here we demonstrate that a mutualistic bacterial endosymbiont of grain weevils maintains and expresses inv/spa genes encoding a type III secretion system homologous to that used for invasion by bacterial pathogens. Phylogenetic analyses indicate that inv/spa genes were present in presymbiotic ancestors of the weevil endosymbionts, occurring at least 50 million years ago. The function of inv/spa genes in maintaining symbiosis is demonstrated by the up-regulation of their expression under both in vivo and in vitro conditions that coincide with host cell invasion.
- Published
- 2002