Perspective
Fate of Culex pipiens: Vector of Many Pathogenic Viruses
Asian Network for Scientific Information, Faisalabad, Pakistan
Saba Munir
Asian Network for Scientific Information, Faisalabad, Pakistan
Wolbachia are intercellular bacteria, infecting almost 66% of the pest (arthropods and nematodes), so it has great potential as biological control (Hilgenboecker et al., 2008). Wolbachia inherit maternally; it shortens the life span of its host and can efficiently cause Cytoplasmic Incompatibility (CI) (McMeniman et al., 2009). Wolbachia also cause infection in common house mosquito C. pipiens but rarely cause infertility, which is due to the presence of compatible Wolbachia strains (Duron et al., 2011; Walker et al., 2009). Atyame et al. (2011) conducted the PCR study of Wolbachia (wPip) strains in Culex pipiens mosquitoes, which sort out the reasons of compatibility and incompatibility caused by Wolbachia. The incompatible Wolbachia strains cause CI in mosquitoes and vice versa. According to them this CI property of Wolbachia depends upon mod and resc (lock and key) model and to evaluate its properties a total of 360 C. pipiens from 15 natural breeding sites of La Reunion Island were examined. From these mosquitoes 11 wPip strains were isolated; mobile genetic elements markers differentiate these strains on the basis of 1-4 genetic markers. These strains were genetically very similar as they contain the same sequence of different ank2, pk1, pk2, GP12 and GP15 alleles. Moreover these strains were mutually bidirectionally compatible. They also introduce the 4 new genetically distinct (w5, w10, w1 and w31) wPip strains from 4 different C. pipiens of different geographical areas. The sequence analysis showed the La Reunion Islands wPip strains were extremely different from these 4 newly introduced strains. All the strains have different mod/resc functions having 11 compatible/incompatible crossing types out of which 5 compatible crossing types were identified in La Reunion Island. These different crossing types results due to the multiple mod and resc abilities i.e., one resc key would be compatible to more than one mod lock. These crossing types determine the viability and non-viability of C. pipiens eggs. The mating between C. pipiens with incompatible wPip strains would result in non-viable eggs with 0% egg Hatching Rate (HR). But the mosquitoes with compatible strains can produce viable eggs with HR more than 90%. Moreover, mating of infected males with uninfected females results in CI. These all mod and resc events occurring in host body are independent to the host genome. Thus this can be said that the mating compatibility of mosquitoes depends upon the Wolbachia strain present in them. If new genetically different Wolbachia strains are introduced in the La Reunion Island there will be more crossing types. Moreover the CI property of Wolbachia strains depends upon their crossing type and not on the host nuclear machinery.
C. pipiens is the potential vector of many viruses which infect both animals and humans. Wolbachia can be used as biological control of this insect as it causes the Cytoplasmic Incompatibility (CI) in C. pipiens. The C. pipiens of La Reunion Island has only genetically similar and compatible strains of Wolbachia therefore no CI was observed. But if the genetically different and incompatible strains of Wolbachia are introduced in this area then the CI can be increased in the mosquitoes. Thus the invasion of mosquitoes population may be stopped by the intrusions of incompatible Wolbachia strains. This study conducted by Atyame et al. (2011) provides more detailed understanding of Wolbachia mode of action at molecular level, in future more research is required in order to use this bacteria more effectively against pathogens.