Identification and Localization of a <i>Rickettsia</i> sp. in <i>Bemisia tabaci</i> (Homoptera: Aleyrodidae)

TLDR

Whiteflies are sap‑sucking insects that host obligate symbiont Portiera aleyrodidarum in a bacteriome and a diverse facultative microbiome including Hamiltonella, Arsenophonus, Fritchea, Wolbachia, and Cardinium, but the role of Rickettsia in their biology remains unknown. The study aimed to characterize the bacterial community of the B biotype of Bemisia tabaci and identify any Rickettsia species present. Researchers used molecular fingerprinting, PCR, and fluorescence in situ hybridization to map Rickettsia distribution, transmission, and localization, proposing that the bacterium enters oocytes with bacteriocytes, multiplies during embryogenesis, and spreads throughout the nymph while avoiding bacteriomes. Rickettsia was detected for the first time in this insect family, present in all 20 Israeli B.

Abstract

ABSTRACT Whiteflies (Homoptera: Aleyrodidae) are sap-sucking insects that harbor “ Candidatus Portiera aleyrodidarum,” an obligatory symbiotic bacterium which is housed in a special organ called the bacteriome. These insects are also home for a diverse facultative microbial community which may include Hamiltonella , Arsenophonus , Fritchea , Wolbachia , and Cardinium spp. In this study, the bacteria associated with a B biotype of the sweet potato whitefly Bemisia tabaci were characterized using molecular fingerprinting techniques, and a Rickettsia sp. was detected for the first time in this insect family. Rickettsia sp. distribution, transmission and localization were studied using PCR and fluorescence in situ hybridizations (FISH). Rickettsia was found in all 20 Israeli B. tabaci populations screened but not in all individuals within each population. A FISH analysis of B. tabaci eggs, nymphs, and adults revealed a unique concentration of Rickettsia around the gut and follicle cells, as well as a random distribution in the hemolymph. We postulate that the Rickettsia enters the oocyte together with the bacteriocytes, leaves these symbiont-housing cells when the egg is laid, multiplies and spreads throughout the egg during embryogenesis and, subsequently, disperses throughout the body of the hatching nymph, excluding the bacteriomes. Although the role Rickettsia plays in the biology of the whitefly is currently unknown, the vertical transmission on the one hand and the partial within-population infection on the other suggest a phenotype that is advantageous under certain conditions but may be deleterious enough to prevent fixation under others.