Host-symbiont co-speciation and reductive genome evolution in gut symbiotic bacteria of acanthosomatid stinkbugs

Yoshitomo Kikuchi, Takahiro Hosokawa, Naruo Nikoh, Xian Ying Meng, Yoichi Kamagata, Takema Fukatsu

研究成果: ジャーナルへの寄稿学術誌査読

170 被引用数 (Scopus)


Background: Host-symbiont co-speciation and reductive genome evolution have been commonly observed among obligate endocellular insect symbionts, while such examples have rarely been identified among extracellular ones, the only case reported being from gut symbiotic bacteria of stinkbugs of the family Plataspidae. Considering that gut symbiotic communities are vulnerable to invasion of foreign microbes, gut symbiotic associations have been thought to be evolutionarily not stable. Stinkbugs of the family Acanthosomatidae harbor a bacterial symbiont in the midgut crypts, the lumen of which is completely sealed off from the midgut main tract, thereby retaining the symbiont in the isolated cryptic cavities. We investigated histological, ecological, phylogenetic, and genomic aspects of the unique gut symbiosis of the acanthosomatid stinkbugs. Results: Phylogenetic analyses showed that the acanthosomatid symbionts constitute a distinct clade in the γ-Proteobacteria, whose sister groups are the obligate endocellular symbionts of aphids Buchnera and the obligate gut symbionts of plataspid stinkbugs Ishikawaella. In addition to the midgut crypts, the symbionts were located in a pair of peculiar lubricating organs associated with the female ovipositor, by which the symbionts are vertically transmitted via egg surface contamination. The symbionts were detected not from ovaries but from deposited eggs, and surface sterilization of eggs resulted in symbiont-free hatchlings. The symbiont-free insects suffered retarded growth, high mortality, and abnormal morphology, suggesting important biological roles of the symbiont for the host insects. The symbiont phylogeny was generally concordant with the host phylogeny, indicating host-symbiont co-speciation over evolutionary time despite the extracellular association. Meanwhile, some local host-symbiont phylogenetic discrepancies were found, suggesting occasional horizontal symbiont transfers across the host lineages. The symbionts exhibited AT-biased nucleotide composition, accelerated molecular evolution, and reduced genome size, as has been observed in obligate endocellular insect symbionts. Conclusion: Comprehensive studies of the acanthosomatid bacterial symbiosis provide new insights into the genomic evolution of extracellular symbiotic bacteria: host-symbiont co-speciation and drastic genome reduction can occur not only in endocellular symbiotic associations but also in extracellular ones. We suggest that many more such cases might be discovered in future surveys.

ジャーナルBMC biology
出版ステータス出版済み - 1月 15 2009

!!!All Science Journal Classification (ASJC) codes

  • バイオテクノロジー
  • 構造生物学
  • 生態、進化、行動および分類学
  • 生理学
  • 生化学、遺伝学、分子生物学(全般)
  • 農業および生物科学(全般)
  • 植物科学
  • 発生生物学
  • 細胞生物学


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