Observing new Wolbachia pipientis genotype increasing heat stress resistance of Drosophila melanogaster host

Maternally transmitted endocellular bacteria Wolbachia is a well-known symbiont of insects, demonstrating both negative and positive effects on host fitness. Previously found Wolbachia strain wMelPlus is characterized by a positive effect on stress-resistance of its host Drosophila melano-gaster under heat stress conditions. This investigation is dedicated to studying the genomic under-pinnings of such an effect. We have sequenced two closely related Wolbachia strains – wMelPlus and wMelCS112, assembled their complete genomes and performed comparative genomic analysis engaging available Wolbachia genomes from wMel and wMelCS groups. Despite the two strains under study share very close gene composition, we have discovered a large (>1/6 of total genome) chromosomal inversion in wMelPlus spanning through the region that includes the area of the inversion earlier found in wMel group of Wolbachia genotypes. A number of genes in unique in-version blocks of wMelPlus have been identified that might be involved in induction of a stress-resistant phenotype in the host. We hypothesize that such an inversion could rearrange es-tablished genetic regulatory networks, causing the observed effects of such a complex fly pheno-type as a modulation of heat stress resistance. Based on our findings, we propose wMelPlus to be distinguished as a separate genotype of wMelCS group, named wMelCS3.