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Wolbachia superinfections and the expression of cytoplasmic incompatibility
S P Sinkins1, H R Braig, S L O'Neill
1Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Abstract:
Strains of Drosophila simulans from Riverside, California (DSR) and Hawaii (DSH) harbour distinct strains of the cytoplasmic incompatibility microorganism Wolbachia, resulting in the expression of bidirectional incompatibility when crossed. D. simulans lines carrying both of these (superinfected) Wolbachia strains were generated by the transfer of infected DSH cytoplasm into DSR embryos by microinjection. The superinfected flies were unidirectionally incompatible with both DSR and DSH individuals. As a result of this pattern, the superinfected state was observed to replace single infections in laboratory populations. The ability of the superinfection to spread was modulated by the production of singly infected offspring from superinfected mothers: strain segregation was observed under crowded larval rearing conditions. An inverse correlation between the penetrance of the cytoplasmic incompatibility phenotype and the degree of larval crowding was also observed. The findings have implications for the evolution of bidirectionally incompatible strains, and lead to the prediction that superinfections should be relatively common in field populations. Evidence for a natural superinfection in the mosquito Aedes albopictus is discussed. The results also have applied significance for the generation of insect lines capable of driving desirable genes into populations already infected with Wolbachia, thus allowing repeated opportunities for population replacement.
Insights
Superinfection with two Wolbachia strains in Drosophila simulans creates unidirectional incompatibility, potentially replacing single infections. This spread is influenced by larval crowding, impacting insect population dynamics.
Area of Science:
- * Microbiology and Genetics
- * Insect Population Dynamics
Background:
- * Distinct strains of the cytoplasmic incompatibility microorganism Wolbachia are harbored by Drosophila simulans populations from California (DSR) and Hawaii (DSH).
- * These distinct Wolbachia strains result in bidirectional incompatibility when DSR and DSH flies are crossed.
Purpose of the Study:
- * To generate and characterize Drosophila simulans lines with dual Wolbachia infections (superinfections).
- * To investigate the transmission dynamics and population replacement potential of these superinfected lines.
Main Methods:
- * Generation of superinfected D. simulans lines via microinjection of DSH cytoplasm into DSR embryos.
- * Assessment of unidirectional and bidirectional cytoplasmic incompatibility phenotypes.
- * Evaluation of strain segregation and spread under varying larval rearing densities.
Main Results:
- * Superinfected flies exhibited unidirectional incompatibility with both singly infected DSR and DSH individuals.
- * Superinfection was observed to replace single infections in laboratory populations.
- * Strain segregation and reduced incompatibility penetrance occurred under crowded larval conditions, inversely correlating with density.
Conclusions:
- * Superinfections can spread and potentially replace single Wolbachia infections in natural populations.
- * Larval crowding modulates the spread and penetrance of cytoplasmic incompatibility.
- * Findings have implications for understanding Wolbachia evolution and applied uses in insect population control.