Tsubasa Ohbayashi

National Agriculture and Food Research Organization | NARO · Institute for Agro-Environmental Sciences

Significance In general, animals have a mouth for feeding, an anus for defecation, and a gut connecting them for digestion and absorption. However, we discovered that the stinkbug’s gut is functionally disconnected in the middle by a previously unrecognized organ for symbiont sorting, which blocks food fluid and nonsymbiotic bacteria but selectivel...

In the symbiosis of the bean bug Riptortus pedestris with Burkholderia insecticola, the bacteria occupy an exclusive niche in the insect midgut and favor insect development and reproduction. In order to understand how the symbiotic bacteria stably colonize the midgut crypts and which services they provide to the host, we compared the cytology, phys...

Many stinkbugs in the superfamily Coreoidea (Hemiptera: Heteroptera) develop crypts in the posterior midgut, harboring Caballeronia (Burkholderia) symbionts. These symbionts form a monophyletic group in Burkholderia sensu lato, called the "stinkbug-associated beneficial and environmental (SBE)" group, recently reclassified as the new genus Caballer...

Nitrification is a key process in the biogeochemical nitrogen cycle and a major emission source of the greenhouse gas nitrous oxide (N2O). The periplasmic enzyme hydroxylamine oxidoreductase (HAO) is involved in the oxidation of hydroxylamine to nitric oxide in the second step of nitrification, producing N2O as a byproduct. Its three-dimensional st...

Caballeronia insecticola is a bacterium belonging to the Burkholderia genus sensu lato, which is able to colonize multiple environments like soils and the gut of the bean bug Riptortus pedestris. We constructed a saturated Himar1 mariner transposon library and revealed by transposon-sequencing that 498 protein-coding genes constitute the essential...

Although microbial inoculation may be effective for sustainable crop production, detrimental aspects have been argued because of the potential of inoculated microorganisms to behave as invaders and negatively affect the microbial ecosystem. We herein compared the impact of rhizobial inoculation on the soil bacterial community with that of agricultu...

The spatial organization of gut microbiota is crucial for the functioning of the gut ecosystem, although the mechanisms that organize gut bacterial communities in microhabitats are only partially understood. The gut of the insect Riptortus pedestris has a characteristic microbiota biogeography with a multispecies community in the anterior midgut an...

硝化は脱窒と窒素固定とともに生物地球化学的に重要な窒素循環プロセスのひとつである。硝化反応によって，アンモニアが硝酸に変換される過程において，温室効果ガスの 1 種 である一酸化二窒素（N2O）が生成される。さらに，農耕地土壌における硝化反応は窒素肥料成分の地下水への溶脱といった環境汚染や窒素損失にもつながっている。硝化による 窒素損失や N 2O 発生を低減させるために，抜本的な対策が求められている。本稿では，農耕地における「硝化（特にアンモニア酸化）」と「N2O」の 2 点に着目し，まず，硝化反 応に関わる微生物と硝化からの N2O 生成機構を解説した。次に，農耕地土壌における硝化と N2O 発生について，環境要因と微生物の両面から説明した。農耕地土壌における硝化 由来の N 2O 削減...

Members of gut microbiota are confronted by the epithelial immune system suggesting that resistance is crucial for chronical gut colonization. We show that the insect Riptortus pedestris produces massively hundreds of specific antimicrobial peptides (AMPs), the Crypt-specific Cysteine-Rich peptides (CCRs), in the posterior midgut that houses a mono...

Caballeronia insecticola is a bacterium belonging to the Burkholderia genus sensu lato , able to colonize multiple environments like soils and the gut of the bean bug Riptortus pedestris . To identify the essential genome of a bacterium is a first step in the understanding of its lifestyles. We constructed a saturated Himar1 mariner transposon libr...

Significance The insect respiratory system consists of tubular tracheae that transport oxygen to the organs. We show that, in the insect pest Riptortus pedestris , the establishment of an essential symbiosis in the gut with the aerobic bacterial species Burkholderia insecticola triggers the development of an extensive tracheal network enveloping th...

The potent and selective Gq protein inhibitor depsipeptide FR900359 (FR), originally discovered as the product of an uncultivable plant endosymbiont, is synthesized by a complex biosynthetic system comprising two nonribosomal peptide synthetase (NRPS) assembly lines. Here we characterize a cultivable bacterial FR producer, enabling detailed investi...

Bacterial cell shapes may be altered by the cell cycle, nutrient availability, environmental stress, and interactions with other organisms. The bean bug Riptortus pedestris possesses a symbiotic bacterium, Burkholderia insecticola, in its midgut crypts. This symbiont is a typical rod-shaped bacterium under in vitro culture conditions, but changes t...

How host organisms evolved and maintain specific mutualisms with microorganisms is a fundamental question that is subject to intensive research. In the large majority of insect mutualisms, the host-microbe specificity is maintained by a “partner fidelity” mechanism, mainly through direct symbiont transmission from mother to offspring. Such vertical...

In addition to abiotic triggers, biotic factors such as microbial symbionts can alter development of multicellular organisms. Symbiont-mediated morphogenesis is well-investigated in plants and marine invertebrates but rarely in insects despite the enormous diversity of insect-microbe symbioses. The bean bug Riptortus pedestris is associated with Bu...

Significance How are specific host-symbiont mutualisms stabilized without vertical transmission? This is one of the fundamental questions in evolutionary biology. To ensure specificity, animals and plants have evolved sophisticated sorting mechanisms. Theoretical studies proposed another mechanism, so-called “competition-based selection,” where hos...

Insects of the heteropteran superfamilies Coreoidea and Lygaeoidea are consistently associated with symbionts of a specific group of the genus Burkholderia, called the "stinkbug-associated beneficial and environmental (SBE)" group. The symbiosis is maintained by the environmental transmission of symbionts. We investigated European and Japanese popu...

A Gram-negative, aerobic, rod-shaped, non-spore-forming, motile bacterium, designated strain RPE64T, was isolated from the gut symbiotic organ of the bean bug Riptortus pedestris, collected in Tsukuba, Japan, in 2007. 16S rRNA gene sequencing showed that this strain belongs to the Burkholderia glathei clade, exhibiting the highest sequence similari...

The cyclic depsipeptide FR900359 (FR), isolated from the tropical plant Ardisia crenata, displays a strong and selective inhibition of Gq proteins, making it an indispensable pharmacological tool to study Gq-related processes, as well as a promising drug candidate. Gq inhibition is a novel mode of action for defense chemicals and crucial for the ec...

Recent studies have suggested that gut symbionts modulate insect development and reproduction. However, the mechanisms by which gut symbionts modulate host physiologies and the molecules involved in these changes are unclear. To address these questions, we prepared three different groups of the insect Riptortus pedestris: Burkholderia gut symbiont-...