Coevolutionary dynamics of Wolbachia multiply infesting the azuki bean beetle

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To elucidate the evolutionary and ecological status of three different strains (Con, Ori, Aus) of Wolbachia infesting the azuki bean beetle, Callosobruchus chinensis, we studied intra-body interactions among Wolbachia strains experimentally and examined prevailing conditions of Wolbachia in the host population, using computer simulation.(1) Fitness cost of Wolbachia infection on the hostWe quantified the cost of Wolbachia infection on the host fitness. Fitness of the host doubly infected with both Con and Ori was significantly lower than the host singly infected with either Con or Ori. The result shows ilemma of multiple infection" quantitatively.(2) Horizontal gene transfer from Wolbachia to the host insectCross-experiment between the hosts which has either Aus or not showed that the strain Aus followed the segregation pattern of the X-linked gene in F1 and F2 generations. The azuki bean beetle has XY sexual chromosome, and this result showed that Aus is not the bacteria of intracellu … More lar endo-symbiont but the genome fragment transferred on the host X chromosome, which suggests the horizontal gene transfer from the prokaryote to the eukaryote, the host insect.(3) Intra-body interaction between Wolbachia strainsWe quantified interactions between Ori and Con, using quantitative PCR. Cell density of Con was significantly lower in the doubly infected host together with Ori than that in the singly infected host with Con only. Con was suppressed disproportionately by Ori, more than the latter's the cell density, which suggests antagonistic interaction or allelopathy between the two strains.(4) Quantification of cytoplasmic incompatibility by Wolbachia on the hostStrength of cytoplasmic incompatibility was quantified in each strain of Wolbachia. Con showed the complete incompatibility (100% death in the embryo stage), Ori did middle (40% death) and Aus did not have any incompatibility.(5) Simulation analysis using an individual-based model, incorporating metapopulation structureBased on the aforementioned results, we are constructing the individual-based model that incorporates metapopulation structure and flush-crash cycle of local population dynamics. We are analyzing the conditions for multiple co-infection in co-evolutionary dynamics. Less