|Kliot, Adi -|
|Czosnek, Henryk -|
|Ghanim, Murad -|
Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 25, 2014
Publication Date: March 5, 2014
Citation: Kliot, A., Cilia, M., Czosnek, H., Ghanim, M. 2014. Infection of the whitefly Bemisia tabaci with Rickettsia spp. alters its interactions with Tomato yellow leaf curl virus. Journal of Virology. 88(10):5652-60. Interpretive Summary: Many insects, including those that transmit plant viruses, possess bacteria called endosymbionts that live within the insect cells. Some insects depend on endosymbionts for survival and nutrition. The whitefly, Bemisia tabaci, is a worldwide agricultural insect pest and importantly transmits viruses, such as the Tomato yellow leaf curl virus (TYLCV), to most vegetable and staple crops. In the whitefly, most bacterial endosymbionts are confined in a specialized compartment but one, Rickettsia spp., is found distributed throughout the whitefly body. In this study, we compared B. tabaci whiteflies both with and without Rickettsia to test whether infection with Rickettsia altered the ability of the insect to transmit TYLCV. The results show that Rickettsia¬-infected whiteflies take up more virus from infected plants, retain the virus longer in their body, and can transmit the virus with nearly double the efficiency. Importantly, infection with Rickettsia caused the virus to localize to a specific area of the insect gut that is critical for the virus to be transmitted. These results offer some new insights into the involvement of a bacterial endosymbiont in the ability of B. tabaci to serve as a vector for plant viruses. They also suggest reexamining the unprecedented role of Rickettsia and other endosymbionts in shaping the biology of the whitefly in general. The research lays the foundation for further research on novel virus vector management strategies that are based on changing the relationship among the insect, virus, and bacterial endosymbionts.
Technical Abstract: Numerous animal and plant viruses are transmitted by arthropod vectors in a persistent, circulative manner. Tomato yellow leaf curl virus (TYLCV) is transmitted by the sweet potato whitefly Bemisia tabaci. Here we report that infection with Rickettsia spp., a facultative endosymbiont of whiteflies, altered TYLCV- B. tabaci interactions. A B. tabaci strain infected with Rickettsia acquired more TYLCV from infected plants, retained the virus longer and exhibited nearly double the transmission efficiency than a non-infected strain, with the same genetic background. Temporal and spatial antagonistic relationships were discovered between Rickettsia and TYLCV within the whitefly. Along different time course experiments, the levels of virus and Rickettsia within the insect were inversely correlated. Fluorescence in situ hybridization analysis on Rickettsia-infected midguts showed evidence for niche exclusion between Rickettsia and TYLCV. In particular, high levels of the bacterium in the midgut resulted in higher virus concentration in the filter chamber, a favored site for virus translocation along the transmission pathway, while low levels of Rickettsia in the midgut resulted in an even distribution of the virus. Taken together, these results indicate that Rickettsia, by infecting the midgut, increases TYLCV transmission efficacy, adding further insights into the complex association between persistent plant viruses, their insect vectors and microorganisms tenants that reside within these insects.