Molecular detection and identification of Rickettsia endosymbiont in different biotypes of Bemisia tabaci

Abstract

Although Rickettsia are the causative agents of several human and animal diseases, they are also found as endosymbionts of many invertebrates. Such symbionts maintain intimate relationships with their hosts and share common features, including intracellular localisation, maternal inheritance, and ability to influence a wide range of host traits. Others, such as Wolbachia, a genus related to Rickettsia, are known to manipulate arthropod reproduction. These abilities to manipulate the host’s reproduction in their favour allow these bacteria to reach high prevalences, even fixation, within the host population, even though some of these symbionts may also harm the host, e.g., via a lessened life span [1]. Some members of R. bellii group are known to be vertically transmitted with induction of reproductive distortions in several insect species [2]. Conversely, hostspecific pathogenic Rickettsia of the spotted fever and typhus groups are easily transmitted between their ticks and lice vectors to the vertebrate host with unknown effect on host vectors. This suggests evolutionary transition between different life styles, including transmission modes, beneficial or deleterious effects, manipulation of host reproduction, acquisition of new host species, evolution and emergence of vertebrate pathogenecity. To date, the way the different characteristics of Rickettsia have evolved remains unknown but this requires the analysis of different host-bacteria associations. In the framework of a study on the symbiotic bacterial community associated with the major worldwide insect pest Bemisia tabaci, we characterised Rickettsia and other bacterial endosymbionts in different whitefly populations. B. tabaci is a species complex consisting of several genetic groups, among which are the closely related invasive B and Q biotypes. These biotypes are morphologically identical but differ in some important economic traits, such as insecticide resistance, and they are mostly recognised on mitochondrial CO1 gene sequences [3]. The Q biotype is divided into three genetic subgroups named Q1, Q2 and Q3 (or AfricaSL). All individuals harbour an obligatory symbiont and up to six different facultative bacteria, among which is a recently described Rickettsia spp. [4]. Here we establish the phylogenetic position of Rickettsia infecting B. tabaci and analyse correlation between bacterial distribution and variability with B. tabaci genetic groups to analyse the evolutionary history of the association.