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Number of toxin and virulence domains varies across Spiroplasma genus. FastTree phylogeny built from MAFFT nucleotide alignment of concatenated Spiroplasma ftsZ, rpoB, and gyrB sequences and rooted to M. mycoides. All Spiroplasma present in the phylogeny encode at least one domain copy of RIP, OTU, ankyrin, or ETX/MTX2. Bar graphs show the number of domain copies present in each genome for each domain type. Double-helix circles indicate at least one of the domains are found on a plasmid. Phage illustrations indicate domains are found within a phage region of the genome. Red shading represents Apis clade, orange shading represents Citri clade and yellow shading represents Ixodetis clade. Red color text is used for VT Spiroplasma and black color text is used for non-VT Spiroplasma. Small black dots indicate FastTree support values above 0.75.
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Vertically transmitted (VT) microbial symbionts play a vital role in the evolution of their insect hosts. A longstanding question in symbiont research is what genes help promote long-term stability of vertically transmitted lifestyles. Symbiont success in insect hosts is due in part to expression of beneficial or manipulative phenotypes that favor...
Citations
... S13-S15, Supplementary Tables S9A-B). The Spiroplasma-like sequences in the tick genome assembly showed homology with chromosomes and plasmids of three Ixodetis clade Spiroplasma strains: S. ixodetis sHm (GenBank: AP026933, AP026934, AP026935; Arai et al., 2022), S. ixodetis sAtri (GenBank: CP117528, CP117532, CP117533; Moore and Ballinger, 2023), and S. ixodetis Y32 (GenBank: CP127039, CP127040, CP127041, CP127042, CP127043, CP127044). Some homology (67-71% identity) was found with the chromosome of Pachydiplax longipennis associated S. platyhelix PALS-1 (GenBank: CP051215), but not with any of the other Spiroplasma genome sequences in the NCBI database (Supplementary Table S10). ...
The taxa Ixodes ricinus and Ixodes inopinatus are sympatric in Tunisia. The genetics underlying their morphological differences are unresolved. In this study, ticks collected in Jouza-Amdoun, Tunisia, were morphologically identified and sequenced using Oxford Nanopore Technologies. Three complete genome assemblies of I. inopinatus and three of I. ricinus with BUSCO scores of ∼98% were generated, including the reconstruction of mitochondrial genomes and separation of both alleles of the TRPA1, TROSPA and calreticulin genes. Deep sequencing allowed the first descriptions of complete bacterial genomes for “Candidatus Midichloria mitochondrii”, Rickettsia helvetica and R. monacensis from North Africa, and the discovery of extensive integration of parts of the Spiroplasma ixodetis and “Ca. M. mitochondrii” into the nuclear genome of these ticks. Phylogenetic analyses of the mitochondrial genome, the nuclear genes, and symbionts showed differentiation between Tunisian and Dutch ticks, but high genetic similarities between Tunisian I. ricinus and I. inopinatus. Subtraction of the genome assemblies identified the presence of some unique sequences, which could not be confirmed when screening a larger batch of I. ricinus and I. inopinatus ticks using PCR. Our findings yield compelling evidence that I. inopinatus is genetically highly similar, if not identical, to sympatric I. ricinus. Defined morphological differences might be caused by extrinsic factors such as micro-climatic conditions or bloodmeal composition. Our findings support the existence of different lineages of I. ricinus as well of its symbionts/pathogens from geographically dispersed locations.
... parasitic wasps) by the ribosome inactivating protein (RIP), although how the pr otein leav es Spiroplasma and r eac hes its place of action is not known (Ballinger and Perlman 2017 ). To understand the evolutionary origins and mechanisms of Spiroplasmainduced MK and protection phenotypes, it is essential to compare Spiroplasma genomes, whic h ar e known to exhibit high flexibility and fast evolution of loci encoding potential toxins and virulent proteins (Hamilton et al. 2016, Ballinger et al. 2019, Gerth et al. 2021, Massey and Newton 2022, Pollmann et al. 2022, Moore and Ballinger 2023. ...
... The protein SAP269_21490 also sho w ed homology with the Photorhabdus insect-related toxins B (PirB), which is known to exhibit toxicity against lepidopteran and dipteran pests (Duchaud et al. 2003 ). Furthermore, s Ap269 encoded homologs of potential virulence factors described by Moore and Ballinger ( 2023 ), such as EXT/MTX toxin (SAP269_07670), anthrax toxin (SAP269_12940), and spiralin (SAP269_20380) but lacked homologs of the M60 family metalloproteases, glycerol-3-phosphate oxidase ( gloP ) and chitinase ( chiA ). Interestingly, s Ap269 also encoded a high-mobility group (HMG) box protein (SAP269_21420), which plays a critical role in embryonic development in eukaryotes but is r ar e in bacterial genomes . ...
... Spiroplasma exhibit a dynamic and r a pid genomic e volution (Gerth et al. 2021 , Moore andBallinger 2023 ). Although the source of the three S. ixodetis clades in A. pisum is unclear, their genetic diversity and variation in genomic components (e.g. ...
The endosymbiotic bacteria Spiroplasma (Mollicutes) infect diverse plants and arthropods, and some of which induce male killing, where male hosts are killed during development. Male-killing Spiroplasma strains belong to either the phylogenetically distant Citri-Poulsonii or Ixodetis groups. In Drosophila flies, Spiroplasma poulsonii induces male killing via the Spaid toxin. While Spiroplasma ixodetis infects a wide range of insects and arachnids, little is known about the genetic basis of S. ixodetis-induced male killing. Here, we analyzed the genome of S. ixodetis strains in the pea aphid Acyrthosiphon pisum (Aphididae, Hemiptera). Genome sequencing constructed a complete genome of a male-killing strain, sAp269, consisting of a 1.5 Mb circular chromosome and an 80 Kb plasmid. sAp269 encoded putative virulence factors containing either ankyrin repeat, ovarian tumor-like deubiquitinase, or ribosome inactivating protein domains, but lacked the Spaid toxin. Further comparative genomics of Spiroplasma strains in A. pisum biotypes adapted to different host plants revealed their phylogenetic associations and the diversity of putative virulence factors. Although the mechanisms of S. ixodetis-induced male killing in pea aphids remain elusive, this study underlines the dynamic genome evolution of S. ixodetis and proposes independent acquisition events of male-killing mechanisms in insects.
