Rickettsia Infection Benefits Its Whitefly Hosts by Manipulating Their Nutrition and Defense

SIMPLE SUMMARY: Rickettsia is a maternally transmitted endosymbiotic bacterium that infects most insect species. In the current study, we investigated the biological and physiological effects of Rickettsia infection on whitefly, Bemisia tabaci. Our results revealed that infection with Rickettsia increased the fertility, survivorship, and shortened the nymphal developmental duration of whitefly Bemisia tabaci. Rickettsia infected B. tabaci had significantly higher glycogen, soluble sugar and trehalose contents than those of Rickettsia negative B. tabaci individuals. When exposed to the entomopathogenic fungus Akanthomyces attenuatus and the insecticides imidacloprid and spirotetramat, Rickettsia infested B. tabaci had lower mortality rates and higher semi-lethal concentrations (LC(50)). The parasitism by Encarsia formosa was also reduced by Rickettsia infection. ABSTRACT: Endosymbionts play an essential role in the biology, physiology and immunity of insects. Many insects, including the whitefly Bemisia tabaci, are infected with the facultative endosymbiont Rickettsia. However, the mutualism between Rickettsia and its whitefly host remains unclear. This study investigated the biological and physiological benefits of Rickettsia infection to B. tabaci. Results revealed that infection of Rickettsia increased the fertility, the survival rate from nymph to adult and the number of female whiteflies. In addition, this facilitation caused a significant reduction in nymphal developmental duration but did not affect percentage rate of egg hatching. Rickettsia infected B. tabaci had significantly higher glycogen, soluble sugar and trehalose contents than Rickettsia negative B. tabaci individuals. Rickettsia also improved the immunity of its whitefly hosts. Rickettsia infested B. tabaci had lower mortality rates and higher semi-lethal concentrations (LC(50)) when exposed to the fungus Akanthomyces attenuatus and the insecticides imidacloprid and spirotetramat. The percentage of parasitism by Encarsia formosa was also reduced by Rickettsia infection. Overall, Rickettsia infection benefits B. tabaci by improving the nutritional composition of its host, and also protects B. tabaci by enhancing its resistance towards insecticides (imidacloprid and spirotetramat), entomopathogenic fungi (A. attenuatus) and its main parasitoid (E. formosa); all of which could significantly impact on current management strategies.