Zchori-Fein, Einat

ABSTRACT Bemisia tabaci (Hemiptera: Aleyrodidae) is a species complex containing >28 cryptic species, some of which are important crop pests worldwide. Like many other sap-sucking insects, whiteflies harbor an obligatory symbiont, “ Candidatus Portiera aleyrodidarum,” and a number of secondary symbionts. So far, six genera of secondary symbionts have been identified in B. tabaci . In this study, we report and describe the finding of an additional bacterium in the indigenous B. tabaci cryptic species China 1 (formerly known as B. tabaci biotype ZHJ3). Phylogenetic analysis based on the 16S rRNA and gltA genes showed that the bacterium belongs to the Alphaproteobacteria subdivision of the Proteobacteria and has a close relationship with human pathogens of the genus Orientia . Consequently, we temporarily named it Orientia -like organism (OLO). OLO was found in six of eight wild populations of B. tabaci China 1, with the infection rate ranging from 46.2% to 76.8%. Fluorescence in situ hybridization (FISH) of B. tabaci China 1 in nymphs and adults revealed that OLOs are confined to the bacteriome and co-occur with “ Ca . Portiera aleyrodidarum.” The vertical transmission of OLO was demonstrated by detection of OLO at the anterior pole end of the oocytes through FISH. Quantitative PCR analysis of population dynamics suggested a complex interaction between “ Ca . Portiera aleyrodidarum” and OLO. Based on these results, we propose “ Candidatus Hemipteriphilus asiaticus” for the classification of this symbiont from B. tabaci .

ABSTRACT The genome of “ Candidatus Portiera aleyrodidarum,” the primary endosymbiont of the whitefly Bemisia tabaci (Mediterranean species), is reported. It presents a reduced genome (357 kb) encoding the capability to synthetize, or participate in the synthesis of, several amino acids and carotenoids, being the first insect endosymbiont capable of supplying carotenoids.

Previously, analysis of 16S rDNA sequences placed a newly discovered lineage of bacterial symbionts of arthropods in the ‘Bacteroidetes’. This symbiont lineage is associated with a number of diverse host reproductive manipulations, including induction of parthenogenesis in severalEncarsiaparasitoid wasps (Hymenoptera: Aphelinidae). In this study, electron microscopy and phylogenetic analysis of the 16S rRNA andgyrBgenes of symbionts fromEncarsia hispidaandEncarsia pergandiellaare used to describe and further characterize these bacteria. Phylogenetic analyses based on these two genes showed that theEncarsiasymbionts are allied with theCytophaga aurantiacalineage within the ‘Bacteroidetes’, with their closest described relative being the acanthamoeba symbiont ‘CandidatusAmoebophilus asiaticus’. TheEncarsiasymbionts share 97 % 16S rDNA sequence similarity withBrevipalpusmite andIxodestick symbionts and 88 % sequence similarity with ‘CandidatusA. asiaticus’. Electron microscopy revealed that many of the bacteria found in the ovaries of the twoEncarsiaspecies contained a regular, brush-like array of microfilament-like structures that appear to be characteristic of the symbiont. Finally, the role of this bacterium in parthenogenesis induction inE. hispidawas confirmed. Based on phylogenetic analyses and electron microscopy, classification of the symbionts fromEncarsiaas ‘CandidatusCardinium hertigii’ is proposed.