A newly recorded Rickettsia of the Torix group is a recent intruder and an endosymbiont in the whitefly Bemisia tabaci

Abstract

Summary The bacterium Rickettsia is found widely in phytophagous insects and often exerts profound effects on the phenotype and fitness of its hosts. Here, we decrypt a new, independent, phylogenetically ancient Torix Rickettsia endosymbiont found constantly in a laboratory line of an economically important insect Asia II 7, a putative species of the Bemisia tabaci whitefly complex (Hemiptera: Aleyrodidae), and occasionally in field whitefly populations. This new Rickettsia distributes throughout the body of its whitefly host. Genetically, compared to Rickettsia_bellii_MEAM1 found earlier in whiteflies, the new Rickettsia species has more gene families and pathways, which may be important factors in shaping specific symbiotic relationships. We propose the name ‘Candidatus Rickettsia_Torix_Bemisia_tabaci (RiTBt)’ for this new endosymbiont associated with whiteflies. Comparative genomic analyses indicate that RiTBi may be a relatively recent intruder in whiteflies given its low abundance in the field and relatively larger genome compared to Rickettsia_bellii_MEAM1.

Transmission, Tropism, and Biological Impacts of Torix Rickettsia in the Common Bed Bug Cimex lectularius (Hemiptera: Cimicidae)

“…The Rickettsia was a sister group to all other Rickettsia described previously, and the clade were named "torix Rickettsia" (Kikuchi et al, 2002). Torix Rickettsia have since been found across multiple arthropod taxa and seem to be widespread and especially common in species associated with freshwater [e.g., Culicoides midges (Pilgrim et al, 2017), dytiscid water beetles (Küchler et al, 2009), Odonata (Thongprem et al, 2020a), and Amphipoda (Park and Poulin, 2020)], but have also been detected in some terrestrial arthropods, e.g., Araneidae (Goodacre et al, 2006), Siphonaptera (Song et al, 2018), and Hemiptera (Wang et al, 2020). Whilst we now understand symbioses between invertebrates and torix Rickettsia are common, much less is known of their biological significance.…”

Widespread Torix Rickettsia in New Zealand amphipods and the use of blocking primers to rescue host COI sequences

“…rrs is a widely used marker but may be too conserved to resolve phylogenetic relationships among closely related species, while the gltA gene shows more variability. Only 6 studies (including the present one) produced both rrs and gltA sequences 22,23,43,51,52 . gltA sequences are not available for most Torix Rickettsia including endosymbionts of leeches and amoeba, as the reports of Torix Rickettsia from these groups precede the first use of gltA sequences to study Torix Rickettsia 19,20,42,53 .…”

“…Horizontal transmission of Torix Rickettsia among genetically distantly related but spatially co-occurring species may have occurred frequently 16 . The high prevalence of Torix Rickettsia and their stable association with their hosts suggest negligible pathogenic effects of this group 19,22,42,43 . Some Torix Rickettsia may even be beneficial for their hosts.…”

“…4). Two genome sequences of Torix Rickettsia recently became available 23,43 . These genomes have the typical characteristics of Rickettsia (e.g.…”

Impact of a novel Rickettsia symbiont on the life history and virus transmission capacity of its host whitefly (Bemisia tabaci)

“…Recently, a maternally inherited Torix group Rickettsia ( Candidatus Rickettsia Torix Bemisia tabaci , RiTBt) was identified as a new symbiont in two species of the B. tabaci whitefly complex, tentatively named as Asia II 1 and Asia II 7 (Wang et al ., 2019; Wang et al ., 2020). These two species of whitefly are indigenous to Asia, and Asia II 1 has been found to be the major vector of important crop viruses, such as Cotton leaf curl virus and Sri Lankan cassava mosaic virus (Ashfaq et al ., 2014; Wang et al ., 2016; Masood et al ., 2017; Masood & Briddon, 2018; Pan et al ., 2018; Chi et al ., 2020).…”