Detection and phylogenetic analysis of Wolbachia in the Asiatic rice leafroller, Cnaphalocrocis medinalis, in Chinese populations

Abstract

Wolbachia are a group of intracellular inherited endosymbiontic bacteria infecting a wide range of insects. In this study the infection status of Wolbachia (Rickettsiales: Rickettsiaceae) was measured in the Asiatic rice leafroller, Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae), from twenty locations in China by sequencing wsp, ftsZ and 16S rDNA genes. The results showed high infection rates of Wolbachia in C. medinalis populations. Wolbachia was detected in all geographically separate populations; the average infection rate was ~ 62.5%, and the highest rates were 90% in Wenzhou and Yangzhou populations. The Wolbachia detected in different C. medinalis populations were 100% identical to each other when wsp, ftsZ, and 16S rDNA sequences were compared, with all sequences belonging to the Wolbachia B supergroup. Based on wsp, ftsZ and 16S rDNA sequences of Wolbachia, three phylogenetic trees of similar pattern emerged. This analysis indicated the possibility of inter-species and intra-species horizontal transmission of Wolbachia in different arthropods in related geographical regions. The migration route of C. medinalis in mainland China was also discussed since large differentiation had been found between the wsp sequences of Chinese and Thai populations.

Figure 1.

Electrophoresis of PCR products of Wolbachia wsp gene from Cnaphalocrocis medinalis by general primers. M: Molecular size standards, lane 7: negative control, lanes 1–6: different regions of C. medinalis (corresponding population number 1 to 6 in Table 2). High quality figures are available online.

Figure 2.

Electrophoresis of PCR products of Wolbachia ftsZ gene from Cnaphalocrocis medinalis by special primers. M: Molecular size standards, lane 7: negative control, lanes 1–6: different populations of Cnaphalocrocis medinalis (corresponding population code 1 to 6 in Table 2). High quality figures are available online.

Figure 3.

Electrophoresis of PCR products of Wolbachia 16S rDNA gene from Cnaphalocrocis medinalis by special primers. M: Molecular size standards, lane 1: negative control, lanes 2–7: different populations of C. medinalis (corresponding population code 1 to 6 in Table 2). High quality figures are available online.

Figure 4.

The phylogenetic trees of Wolbachia detected in Cnaphalocrocis medinalis and other insects and mites based on their wsp, ftsZ, 16S rDNA sequences. Trees inferred from maximum parsimony and neighbor joining methods (maximum likelihood model) using MEGA 4.0 program were similar though less resolved (data not shown.) The sequences of Ostrinia furnacalis (EU2943 11) and Thecodiplosis japonensis (AF220605), were used as outgroups in Fig. 4A and B, respectively. Additionally, the sequence of Drosophila simulons (AY227742) was used in Fig.4C. High quality figures are available online.