title: Phylogenetic position and peculiar genetic traits of a midgut bacterial symbiont of the stinkbug Parastrachia japonensis.
abstract: The stinkbug Parastrachia japonensis (Hemiptera: Parastrachiidae) is known for its prolonged prereproductive nonfeeding period, maternal care of eggs in an underground nest, and maternal collection and provisioning of food (fruits) for nymphs. A previous study suggested that a bacterial symbiont is involved in uric acid recycling in this insect during the nonfeeding period, but the identity of this symbiont has not been determined. Here we characterized a novel bacterial symbiont obtained from P. japonensis. Molecular phylogenetic analyses based on 16S rRNA, gyrB, and groEL gene sequences consistently indicated that this symbiont constituted a distinct lineage in the Gammaproteobacteria that has no close relatives but is allied with gut symbionts of acanthosomatid and plataspid stinkbugs, as well as with endocellular symbionts of sharpshooters, tsetse flies, and aphids. The symbiont genes had a remarkably AT-biased nucleotide composition and exhibited significantly accelerated molecular evolution. The symbiont genome was extremely reduced; its size was estimated to be 0.85 Mb. These results suggest that there has been an intimate host-symbiont association over evolutionary time. The symbiont was localized in swollen crypts in a posterior part of the midgut, which was a specialized symbiotic organ. The possibility that the symbiont is involved in uric acid recycling is discussed. The designation "Candidatus Benitsuchiphilus tojoi" is proposed for the symbiont.
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8566, Japan. th-hosokawa@aist.go.jp
authors.forename: Takahiro
authors.initials: T
authors.lastname: Hosokawa
authors.forename: Yoshitomo
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: Naruo
authors.initials: N
authors.lastname: Nikoh
authors.forename: Xian-Ying
authors.initials: XY
authors.lastname: Meng
authors.forename: Mantaro
authors.initials: M
authors.lastname: Hironaka
authors.forename: Takema
authors.initials: T
authors.lastname: Fukatsu
mesh_terms: D000818:Animals; D018834:Chaperonin 60 / Q000235:genetics / Q000378:metabolism; D027081:DNA Gyrase / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D020563:Gammaproteobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D041981:Gastrointestinal Tract / Q000382:microbiology*; D020062:Heteroptera / Q000382:microbiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D018834:Chaperonin 60; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D027081:DNA Gyrase
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