Abstract
BackgroundThe whitefly Bemisia tabaci is cryptic species complex composed of numerous species. Individual species from the complex harbor a diversity of bacterial endosymbionts including Wolbachia. However, while Wolbachia is known to have a number of different roles, its role in B. tabaci is unclear. Here, the antibiotic rifampicin is used to selectively eliminate Wolbachia from B. tabaci so as to enable its roles in whitefly development and reproduction to be explored. The indirect effects of Wolbachia elimination on the biology of Encarsia bimaculata, a dominant parasitoid of B. tabaci in South China, were also investigated.Methodology/Principal FindingqRT-PCR and FISH were used to show that after 48 h exposure to 1.0 mg/ml rifampicin, Wolbachia was completely inactivated from B. tabaci Mediterranean (MED) without any significant impact on either the primary symbiont, Portiera aleyrodidarum or any of the other secondary endosymbionts present. For B. tabaci MED, Wolbachia was shown to be associated with decreased juvenile development time, increased likelihood that nymphs completed development, increased adult life span and increased percentage of female progeny. Inactivation was associated with a significant decrease in the body size of the 4th instar which leads us to speculate as to whether Wolbachia may have a nutrient supplementation role. The reduction in nymph body size has consequences for its parasitoid, E. bimaculata. The elimination of Wolbachia lead to a marked increase in the proportion of parasitoid eggs that completed their development, but the reduced size of the whitefly host was also associated with a significant reduction in the size of the emerging parasitoid adult and this was in turn associated with a marked reduction in adult parasitoid longevity.Conclusions/Significance Wolbachia increases the fitness of the whitefly host and provides some protection against parasitization. These observations add to our understanding of the roles played by bacterial endosymbionts.
Highlights
Endosymbiotic, mutualistic and parasitic bacterial endosymbionts that have either obligate or facultative relationships with insects, play an important role in many aspects of insect biology and ecology [1]
As Wolbachia was shown by the above to be the only endosymbiont inactivated by rifampicin under inactive conditions of 1.0 mg/ml for 48 h, we explored whether the inactivation of Wolbachia influenced the biology of B. tabaci and parasitisation of B. tabaci by E. bimaculata
The Detection of Endosymbionts in the MED B. tabaci PCR detection indicated that all seven endosymbionts, the primary obligate endosymbiont P. aleyrodidarum and the six secondary endosymbionts Arsenophonus, Cardinium, Fritschea, Hamiltonella, Rickettsia as well as Wolbachia were present in the populations sampled
Summary
Endosymbiotic, mutualistic and parasitic bacterial endosymbionts that have either obligate or facultative relationships with insects, play an important role in many aspects of insect biology and ecology [1]. Primary endosymbionts are confined to specialized host cells called bacteriocytes that together form an organ called a bacteriome [5] They have an obligatory relationship with the host, are transmitted vertically from mother to offspring and are thought to synthesize essential non-dietary metabolites [1,6,7,8]. Secondary endosymbionts can occur in the bacteriocytes, but are often found in the cells of tissues throughout the host [5,9] These bacteria usually have a facultative relationship with the host and while primarily transmitted vertically from mother to offspring, may be transmitted horizontally through direct and indirect contact with other infected individuals [1,2,9,10]. The indirect effects of Wolbachia elimination on the biology of Encarsia bimaculata, a dominant parasitoid of B. tabaci in South China, were investigated
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