Type III secretion systems and the evolution of mutualistic endosymbiosis.
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.
Dale
Colin
C
Department of Ecology and Evolutionary Biology, Center for Insect Science, and Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ 85721.
Plague
Gordon R
GR
Wang
Ben
B
Ochman
Howard
H
Moran
Nancy A
NA
D018829:Adhesins, Bacterial / Q000235:genetics; D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D001517:Coleoptera / Q000235:genetics* / Q000382:microbiology* / Q000502:physiology; D004269:DNA, Bacterial / Q000235:genetics; D004755:Enterobacteriaceae / Q000235:genetics* / Q000502:physiology*; D015870:Gene Expression; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010802:Phylogeny; D013559:Symbiosis / Q000235:genetics*
D018829:Adhesins, Bacterial; D000942:Antigens, Bacterial; D004269:DNA, Bacterial; C119204:streptococcal protective antigen; C053476:invasin, Yersinia