Cytoplasmic incompatibility in the semivoltine longicorn beetle Acalolepta fraudatrix (Coleoptera: Cerambycidae) double infected with Wolbachia.

Takuya Aikawa,Yu Ichihara,Katsunori Nakamura,Hisashi Anbutsu,Hayato Masuya,Noritoshi Maehara,J Joe Hull

doi:10.1371/journal.pone.0261928

Abstract

Wolbachia are obligatory endosymbiotic α-proteobacteria found in many arthropods. They are maternally inherited, and can induce reproductive alterations in the hosts. Despite considerable recent progress in studies on the associations between Wolbachia and various taxonomic groups of insects, none of the researches have revealed the effects of Wolbachia on longicorn beetles as the host insect. Acalolepta fraudatrix is a forest longicorn beetle that is distributed in East Asia. In this study, the relationship between Wolbachia and A. fraudatrix was investigated. Out of two populations of A. fraudatrix screened for Wolbachia using the genes ftsZ, wsp, and 16S rRNA, only one of the populations showed detection of all three genes indicating the presence of Wolbachia. Electron microscopy and fluorescent in situ hybridization also confirmed that the A. fraudatrix population was infected with Wolbachia. Sequencing the wsp genes derived from single insects revealed that two strains of Wolbachia coexisted in the insects based on the detection of two different sequences of the wsp gene. We designated these strains as wFra1 and wFra2. The bacterial titers of wFra1 were nearly 2-fold and 3-fold higher than wFra2 in the testes and ovaries, respectively. The two strains of Wolbachia in the insects were completely eliminated by rearing the insects on artificial diets containing 1% concentration of tetracycline for 1 generation. Reciprocal crosses between Wolbachia-infected and Wolbachia-uninfected A. fraudatrix demonstrated that only eggs produced by the crosses between Wolbachia-infected males and Wolbachia-uninfected females did not hatch, indicating that Wolbachia infecting A. fraudatrix causes cytoplasmic incompatibility in the host insect. This is the first report showing the effect of Wolbachia on reproductive function in a longicorn beetle, A. fraudatrix.

Highlights

The members of the genus Wolbachia are common intracellular symbionts that are maternally inherited in arthropods and filarial nematodes, and they are estimated to infect up to 60% of insects [1,2,3,4,5,6]
Twenty-three adults and 13 larvae of A. fraudatrix from the Fukaura population, and 10 adults from the Shiwa population were subjected to diagnostic PCR detection of Wolbachia using the ftsZ, wsp, and 16S rRNA genes, and four other symbiotic bacteria, Rickettsia, Spiroplasma, Arsenophonus and Cardinium using the 16S rRNA gene
Direct sequencing of the PCR products of the ftsZ, wsp, and 16S rRNA genes derived from single insects showed overlapping sequence spectra, suggesting that multiple strains of Wolbachia coexist in A. fraudatrix

Summary

Introduction

The members of the genus Wolbachia are common intracellular symbionts that are maternally inherited in arthropods and filarial nematodes, and they are estimated to infect up to 60% of insects [1,2,3,4,5,6]. They are capable of manipulating host reproduction by causing cytoplasmic incompatibility (CI), parthenogenesis, male killing or feminization [7,8,9,10,11]. The ability of Wolbachia to cause these reproductive alterations drives its efficient and rapid spread in host populations [5, 14, 15]

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Results

Conclusion