Mosaic composition of ribA and wspB genes flanking the virB8-D4 operon in the Wolbachia supergroup B-strain, wStr

Abstract

The obligate intracellular bacterium, Wolbachia pipientis (Rickettsiales), is a widespread, vertically transmitted endosymbiont of filarial nematodes and arthropods. In insects, Wolbachia modifies reproduction, and in mosquitoes, infection interferes with replication of arboviruses, bacteria and plasmodia. Development of Wolbachia as a tool to control pest insects will be facilitated by an understanding of molecular events that underlie genetic exchange between Wolbachia strains. Here, we used nucleotide sequence, transcriptional and proteomic analyses to evaluate expression levels and establish the mosaic nature of genes flanking the T4SS virB8-D4 operon from wStr, a supergroup B-strain from a planthopper (Hemiptera) that maintains a robust, persistent infection in an Aedes albopictus mosquito cell line. Based on protein abundance, ribA, which contains promoter elements at the 5′-end of the operon, is weakly expressed. The 3′-end of the operon encodes an intact wspB, which encodes an outer membrane protein and is co-transcribed with the vir genes. WspB and vir proteins are expressed at similar, above average abundance levels. In wStr, both ribA and wspB are mosaics of conserved sequence motifs from Wolbachia supergroup A- and B-strains, and wspB is nearly identical to its homolog from wCobU4-2, an A-strain from weevils (Coleoptera). We describe conserved repeated sequence elements that map within or near pseudogene lesions and transitions between A- and B-strain motifs. These studies contribute to ongoing efforts to explore interactions between Wolbachia and its host cell in an in vitro system.Electronic supplementary materialThe online version of this article (doi:10.1007/s00203-015-1154-8) contains supplementary material, which is available to authorized users.

Temperature effects on cellular host-microbe interactions explain continent-wide endosymbiont prevalence

“…We conclude that the premature wspB stop codon is likely a significant contributor to differences in wMel oocyte abundance in the cold (Figure 3D; see detailed description in Method details). The stop codon occurs in an outer loop region of WspB that is otherwise conserved among wMel-like strains (diverged up to 62,000 years ago 41 ) and B-group Wolbachia (diverged up to 46 million years ago 46 ), just before a hypervariable region likely involved in Wolbachia-host interactions 76 (Figure 3E; Table S2). The specific function of WspB is unknown in Wolbachia; 1,76 however, wspB is co-transcribed as part of the virB8-D4 operon that encodes components of the Wolbachia T4SS.…”

“…The stop codon occurs in an outer loop region of WspB that is otherwise conserved among wMel-like strains (diverged up to 62,000 years ago 41 ) and B-group Wolbachia (diverged up to 46 million years ago 46 ), just before a hypervariable region likely involved in Wolbachia-host interactions 76 (Figure 3E; Table S2). The specific function of WspB is unknown in Wolbachia; 1,76 however, wspB is co-transcribed as part of the virB8-D4 operon that encodes components of the Wolbachia T4SS. 76 Our optimal model for WspB structure (Figure 3F) was built using the template Opa60, an outer membrane protein in pathogenic Neisseria that induces phagocytosis by human host cells.…”

“…The specific function of WspB is unknown in Wolbachia; 1,76 however, wspB is co-transcribed as part of the virB8-D4 operon that encodes components of the Wolbachia T4SS. 76 Our optimal model for WspB structure (Figure 3F) was built using the template Opa60, an outer membrane protein in pathogenic Neisseria that induces phagocytosis by human host cells. 77 The long extracellular loops with hypervariable regions (HVRs) strongly suggest that WspB is similarly involved with the recognition of host cells, for example, in developing ooctyes.…”

“…These loops contain hypervariable regions, which were previously hypothesized to be involved with Wolbachia-host interactions (Table S2). 76 The b-barrel domain of WspB could be indicative of a porin, but the small diameter of the pore would limit molecular transport to solvent and small ions, excluding larger Wolbachia effector proteins. 72 Lastly, we examined sequence variation in wspB homologs of closely related wMel-like Wolbachia strains 41 (wYak, wSan, wTei, 41 and wAu 134 ) and other previously reported A-and B-group Wolbachia strains.…”

“…72 Lastly, we examined sequence variation in wspB homologs of closely related wMel-like Wolbachia strains 41 (wYak, wSan, wTei, 41 and wAu 134 ) and other previously reported A-and B-group Wolbachia strains. 76 Wolbachia pool-seq analysis We treated the 43 SNPs distinguishing temperate and tropical wMel as candidate loci that may be linked to differences in wMel localization within female oocytes. First, we tested whether temperate wMel alleles occur at higher frequency in temperate host populations in Australia using publicly available pool-seq data from isofemales lines of D. melanogaster in temperate Tasmania and tropical Queensland (GenBank BioProject: PRJNA237820).…”