Euglenozoan kleptoplasty illuminates the early evolution of photoendosymbiosis.

Kleptoplasts (kP) are distinct among photosynthetic organelles in eukaryotes (i.e., plastids) because they are routinely sequestered from prey algal cells and function only temporarily in the new host cell. Therefore, the hosts of kleptoplasts benefit from photosynthesis without constitutive photoendosymbiosis. Here, we report that the euglenozoan Rapaza viridis has only kleptoplasts derived from a specific strain of green alga, Tetraselmis sp., but no canonical plastids like those found in its sister group, the Euglenophyceae. R. viridis showed a dynamic change in the accumulation of cytosolic polysaccharides in response to light-dark cycles, and 13C isotopic labeling of ambient bicarbonate demonstrated that these polysaccharides originate in situ via photosynthesis; these data indicate that the kleptoplasts of R. viridis are functionally active. We also identified 276 sequences encoding putative plastid-targeting proteins and 35 sequences of presumed kleptoplast transporters in the transcriptome of R. viridis. These genes originated in a wide range of algae other than Tetraselmis sp., the source of the kleptoplasts, suggesting a long history of repeated horizontal gene transfer events from different algal prey cells. Many of the kleptoplast proteins, as well as the protein-targeting system, in R. viridis were shared with members of the Euglenophyceae, providing evidence that the early evolutionary stages in the green alga-derived secondary plastids of euglenophytes also involved kleptoplasty.

An Enigmatic Stramenopile Sheds Light on Early Evolution in Ochrophyta Plastid Organellogenesis.

Ochrophyta is an algal group belonging to the Stramenopiles and comprises diverse lineages of algae which contribute significantly to the oceanic ecosystems as primary producers. However, early evolution of the plastid organelle in Ochrophyta is not fully understood. In this study, we provide a well-supported tree of the Stramenopiles inferred by the large-scale phylogenomic analysis that unveils the eukaryvorous (nonphotosynthetic) protist Actinophrys sol (Actinophryidae) is closely related to Ochrophyta. We used genomic and transcriptomic data generated from A. sol to detect molecular traits of its plastid and we found no evidence of plastid genome and plastid-mediated biosynthesis, consistent with previous ultrastructural studies that did not identify any plastids in Actinophryidae. Moreover, our phylogenetic analyses of particular biosynthetic pathways provide no evidence of a current and past plastid in A. sol. However, we found more than a dozen organellar aminoacyl-tRNA synthases (aaRSs) that are of algal origin. Close relationships between aaRS from A. sol and their ochrophyte homologs document gene transfer of algal genes that happened before the divergence of Actinophryidae and Ochrophyta lineages. We further showed experimentally that organellar aaRSs of A. sol are targeted exclusively to mitochondria, although organellar aaRSs in Ochrophyta are dually targeted to mitochondria and plastids. Together, our findings suggested that the last common ancestor of Actinophryidae and Ochrophyta had not yet completed the establishment of host-plastid partnership as seen in the current Ochrophyta species, but acquired at least certain nuclear-encoded genes for the plastid functions.

Ectopic accumulation of ceramide in cardiomyocytes modulates alcoholic cardiomyopathy via the TLR4-dependent pathway.

BACKGROUND AND AIMS: Excessive alcohol consumption predisposes drinkers to develop alcoholic cardiomyopathy. Although cardiomyocyte loss is the hallmark of cardiomyopathy, the underlying mechanism remains elusive. This study examined the potential mechanism of alcohol-induced cardiomyocyte death in a mouse model of alcoholic cardiomyopathy. METHODS: We established the alcoholic cardiomyopathy mouse model using C57BL/6J mice and confirmed it via echocardiography and histological examination. The cardiac ceramide content and profile were analyzed with a triple-quadrupole mass spectrometer. The molecular mechanism underlying the accumulation of ceramide due to chronic alcohol consumption and ceramide-induced cardiomyocyte death were investigated by in vivo and in vitro models. Finally, we established a TLR4 mutation model to explore the function of TLR4 in CH3/HeJ mice. RESULTS: Cardiac lipotoxicity that followed alcohol exposure resulted mainly in C16:0-, C18:0-, and C24:1-ceramide aggregation. Genes encoding the sphingosine hydrolysis enzymes (SMPD1 and SMPD2) rather than de novo synthetic biomarkers were markedly upregulated. Exogenous ceramide mimics (C6-ceramide) werenderlying the accumulation of ceramide observed to cause H9C2 cardiomyocyte-like cell death, which was consistent with results under palmate acid (PA) treatment. As a ceramide precursor, PA induces intracellular ceramide generation through TLR4 signaling, which can be abolished by an inhibitor of ceramide synthesis. Furthermore, mechanistic investigations demonstrated that pharmacological or genetic inhibition of TLR4 attenuated PA-induced cell death and corresponding ceramide production. Moreover, global mutation of TLR4 in CH3/HeJ mice significantly reduced the accumulation of C24:0, C24:1, OH_C24:1, and total ceramide following alcohol challenge. CONCLUSIONS: Our findings demonstrate that ceramide accumulation plays a crucial role in alcoholic cardiomyopathy, effects that are partially mediated through the TLR4-dependent pathway.

Inositol Hexakis Phosphate is the Seasonal Phosphorus Reservoir in the Deciduous Woody Plant Populus alba L.

Seasonal recycling of nutrients is an important strategy for deciduous perennials. Deciduous perennials maintain and expand their nutrient pools by the autumn nutrient remobilization and the subsequent winter storage throughout their long life. Phosphorus (P), one of the most important elements in living organisms, is remobilized from senescing leaves during autumn in deciduous trees. However, it remains unknown how phosphate is stored over winter. Here we show that in poplar trees (Populus alba L.), organic phosphates are accumulated in twigs from late summer to winter, and that IP6 (myo-inositol-1,2,3,4,5,6-hexakis phosphate: phytic acid) is the primary storage form. IP6 was found in high concentrations in twigs during winter and quickly decreased in early spring. In parenchyma cells of winter twigs, P was associated with electron-dense structures, similar to globoids found in seeds of higher plants. Various other deciduous trees were also found to accumulate IP6 in twigs during winter. We conclude that IP6 is the primary storage form of P in poplar trees during winter, and that it may be a common strategy for seasonal P storage in deciduous woody plants.

Ultrastructure of the bacteriome and bacterial symbionts in the Asian citrus psyllid, Diaphorina citri.

IMPORTANCE: Omics analyses suggested a mutually indispensable tripartite association among the host D. citri and organelle-like bacteriome associates, Carsonella and Profftella, which are vertically transmitted through host generations. This relationship is based on the metabolic complementarity among these organisms, which is partly enabled by horizontal gene transfer between partners. However, little was known about the fine morphology of the symbionts and the bacteriome, the interface among these organisms. As a first step to address this issue, the present study performed transmission electron microscopy, which revealed previously unrecognized ultrastructures, including aggregations of ribosomes in Carsonella, numerous tubes and occasional protrusions of Profftella, apparently degrading Profftella, and host organelles with different abundance and morphology in distinct cell types. These findings provide insights into the behaviors of the symbionts and host cells to maintain the symbiotic relationship in D. citri.

Report of three centrohelid heliozoan species (Centroplasthelida Febre-Chevalier et Febre) from new localities in Europe with notes on their distribution.

Raphidocystis marginata (Siemensma, 1981), Raineriophrys echinata (Rainer, 1968), and Pterocystis fortesca (Nicholls, 1983) are heliozoan protists, have been recorded only in a few localities in Europe, and considered to be rare species. These centrohelid heliozoans have been reported for the first time in Ukrainian Polissia, and we provide their morphological descriptions with new morphometric data of exoskeleton (periplast) based on Ukrainian material. The diagnostic morphological characters are illustrated by light and scanning electron microscope photographs. Their geographical distribution in Europe and biotope preference are discussed.

Morphological reconstruction during cell regeneration in the ciliate Spirostomum ambiguum.

When the ciliate Spirostomum ambiguum is transected into two pieces, both fragments regenerate and proliferate. In the anterior fragments, which have lost their contractile vacuoles due to transection, new contractile vacuoles were formed at their posterior ends in a few minutes. When the cells were cut into three pieces, new contractile vacuoles were formed in the anterior and middle fragments, both at their posterior ends. Thus, the anterior-posterior axis of S. ambiguum was maintained after transection. Morphological repair, including the formation of the contractile vacuole, was also observed when only the anteriormost portion was transected to cut out a small fragment that did not contain part of the macronucleus. Scanning electron microscopy was performed to observe changes in the shape of the cleavage surface of S. ambiguum during the wound healing process. Within minutes after cutting, the cut surface was covered with a cilia-free membrane, preventing leakage of cytoplasmic contents. The surface of the cut area then rounded with time and was covered with cilia, completing the repair of the cut area in about one day.

Studies on vacuolar membrane microdomains isolated from Arabidopsis suspension-cultured cells: local distribution of vacuolar membrane proteins.

The local distribution of both the vacuolar-type proton ATPase (V-ATPase) and the vacuolar-type proton pyrophosphatase (V-PPase), the main vacuolar proton pumps, was investigated in intact vacuoles isolated from Arabidopsis suspension-cultured cells. Fluorescent immunostaining showed that V-PPase was distributed evenly on the vacuolar membrane (VM), but V-ATPase localized to specific regions of the VM. We hypothesize that there may be membrane microdomains on the VM. To confirm this hypothesis, we prepared detergent-resistant membranes (DRMs) from the VM in accordance with well established conventional methods. Analyses of fatty acid composition suggested that DRMs had more saturated fatty acids compared with the whole VM in phosphatidylcholine and phosphatidylethanolamine. In the proteomic analyses of both DRMs and detergent-soluble mebranes (DSMs), we confirmed the different local distributions of V-ATPase and V-PPase. The observations of DRMs with an electron microscope supported the existence of different areas on the VM. Moreover, it was observed using total internal reflection fluorescent microscopy (TIRFM) that proton pumps were frequently immobilized at specific sites on the VM. In the proteomic analyses, we also found that many other vacuolar membrane proteins are distributed differently in DRMs and DSMs. Based on the results of this study, we discuss the possibility that VM microdomains might contribute to vacuolar dynamics.

Siliceous scales in the centrohelid heliozoan Raphidocystis contractilis facilitate settlement to the substratum.

The centrohelid heliozoan Raphidocystis contractilis has hundreds of small scales on the surface of the cell body. To understand the biological functions of the scales, comparative examinations were conducted between wild-type and scale-deficient strains that has naturally lost scales after long-term cultivation. The scale-deficient strain exhibited decreased adhesion to the substratum and had a lower sedimentation rate in water than the wild-type strain, suggesting that the scale may have the ability to attach quickly and strongly to the substratum. Percoll density gradient centrifugation showed that the scale-deficient strain had a lower density than that of the wild-type strain. In the wild-type strain, more scaled cells were observed in the higher specific gravity fractions. During the long-term culture of cells, only the cells suspended in the upper area of the flask were transferred to fresh medium. By repeating this procedure, we may have selected only cells that did not possess normal scales. In the natural environment, centrohelid heliozoans are easily flushed away if they cannot adhere strongly to the bottom. These results suggest that they use scales to ensure effective adhesion to the substratum.

SEM observation of non-fixed and water freeze-dried Spirostomum ambiguum.

We aimed to freeze-dry the ciliate Spirostomum ambiguum, obtained from water, without fixation and observe it using scanning electron microscopy (SEM). Living cells were placed on a specimen stub and frozen upon contact with a Cu block kept at either -80 °C or -100 °C. Samples were then freeze-dried and observed by SEM. In most cases, no damage to the specimen due to ice crystal formation was observed. Because of the instantaneous freezing, the metachronal wave of cilia on the body surface of the ciliate was well preserved. Approximately 70-80% of cells were preserved in the contracted state due to inevitable exposure to mechanical vibration immediately before freezing. The remaining samples were preserved in a fully-extended state. Morphometric measurements of the cell surface showed that in the extended state, ciliary rows were almost parallel to the long axis of the cell, whereas in the contracted state, they were twisted in a left-handed helix at an angle of 45-65°. The distance between adjacent cilia along a ciliary row was 1.88 ± 0.43 µm in the extended state and 1.32 ± 0.41 µm in the contracted state (mean ± SD). However, the spacing between adjacent ciliary rows remained unchanged.

Eukaryote-to-eukaryote gene transfer gives rise to genome mosaicism in euglenids.

BACKGROUND: Euglenophytes are a group of photosynthetic flagellates possessing a plastid derived from a green algal endosymbiont, which was incorporated into an ancestral host cell via secondary endosymbiosis. However, the impact of endosymbiosis on the euglenophyte nuclear genome is not fully understood due to its complex nature as a 'hybrid' of a non-photosynthetic host cell and a secondary endosymbiont. RESULTS: We analyzed an EST dataset of the model euglenophyte Euglena gracilis using a gene mining program designed to detect laterally transferred genes. We found E. gracilis genes showing affinity not only with green algae, from which the secondary plastid in euglenophytes evolved, but also red algae and/or secondary algae containing red algal-derived plastids. Phylogenetic analyses of these 'red lineage' genes suggest that E. gracilis acquired at least 14 genes via eukaryote-to-eukaryote lateral gene transfer from algal sources other than the green algal endosymbiont that gave rise to its current plastid. We constructed an EST library of the aplastidic euglenid Peranema trichophorum, which is a eukaryovorous relative of euglenophytes, and also identified 'red lineage' genes in its genome. CONCLUSIONS: Our data show genome mosaicism in E. gracilis and P. trichophorum. One possible explanation for the presence of these genes in these organisms is that some or all of them were independently acquired by lateral gene transfer and contributed to the successful integration and functioning of the green algal endosymbiont as a secondary plastid. Alternative hypotheses include the presence of a phagocytosed alga as the single source of those genes, or a cryptic tertiary endosymbiont harboring secondary plastid of red algal origin, which the eukaryovorous ancestor of euglenophytes had acquired prior to the secondary endosymbiosis of a green alga.

Characterization of a green Stentor with symbiotic algae growing in an extremely oligotrophic environment and storing large amounts of starch granules in its cytoplasm.

The genus Stentor is a relatively well-known ciliate owing to its lucid trumpet shape. Stentor pyriformis represents a green, short, and fat Stentor, but it is a little-known species. We investigated 124 ponds and wetlands in Japan and confirmed the presence of S. pyriformis at 23 locations. All these ponds were noticeably oligotrophic. With the improvement of oligotrophic culture conditions, we succeeded in long-term cultivation of three strains of S. pyriformis. The cytoplasm of S. piriformis contains a large number of 1-3 µm refractive granules that turn brown by Lugol's staining. The granules also show a typical Maltese-cross pattern by polarization microscopy, strongly suggesting that the granules are made of amylopectin-rich starch. By analyzing the algal rDNA, it was found that all S. pyriformis symbionts investigated in this study were Chlorella variabilis. This species is known as the symbiont of Paramecium bursaria and is physiologically specialized for endosymbiosis. Genetic discrepancies between C. variabilis of S. pyriformis and P. bursaria may indicate that algal sharing was an old incident. Having symbiotic algae and storing carbohydrate granules in the cytoplasm is considered a powerful strategy for this ciliate to withstand oligotrophic and cold winter environments in highland bogs.

The effects of phospholipids and fatty acids on the oligomer formation of NAP-22.

Recovery of various signal transduction molecules in the detergent-resistant membrane microdomain (DRM) fraction suggests the importance of this region in cellular functions. NAP-22 (also called BASP1 or CAP-23) is a neuron-enriched calmodulin-binding protein and one of the major proteins in the DRM fraction of the neuronal cell membrane. Previous studies showed tight binding activity of NAP-22 to acidic membrane lipids and the self-interaction of NAP-22, i.e., oligomerization. In this study, the effect of various phospholipids, lysophospholipids and fatty acids on the oligomerization of NAP-22 was studied through SDS-PAGE after chemical cross-linking and electron microscopic observation. High molecular mass oligomers were detected by SDS-PAGE after incubation in solutions containing over 20 mM NaCl at pH 6.5-8.5, even in the absence of lipid addition, and the addition of Ca2+/calmodulin abolished oligomerization. Higher molecular mass oligomer formation after incubation with acidic phospholipids was detected with gradient SDS-PAGE. Much higher mass oligomers were detected in the presence of polyunsaturated fatty acids. Electron microscopic analysis of the samples after SDS treatment showed tangled rope-like structures. Liposome-bound NAP-22 showed small oval or annular structures after cross-linking and SDS treatment. These oligomers were suggested to make the tangled rope-like structures, for annular structures of the same size were observed in the structure. These results suggest the participation of NAP-22 to liquid-liquid phase separation through oligomerization.

Pediludiella daitoensis gen. et sp. nov. (Scenedesmaceae, Chlorophyceae), a large coccoid green alga isolated from a Loxodes ciliate.

Freshwater protists often harbor unicellular green algae within their cells. In ciliates, possibly because of large host cell sizes and the small size of algal coccoids, a single host cell typically contains more than a hundred algal cells. While surveying such algae-bearing protists on Minami Daito Jima Island in Japan, we found a green Loxodes ciliate (Loxodida, Karyorelictea) that contained one or two dozens of very large coccoid algae. We isolated one of these algae and analyzed its characteristics in detail. A small subunit (SSU) rDNA phylogeny indicated Pseudodidymocystis species (Scenedesmaceae, Chlorophyceae) to be the taxon closest to the alga, although it was clearly separated from this by 39 or more different sites (inclusive of gaps). SSU rRNA structure analyses indicated that these displacements included eight compensatory base changes (CBCs) and seven hemi-CBCs. We therefore concluded that this alga belongs to a separate genus, and described it as Pediludiella daitoensis gen. et sp. nov. The shape of the isolated and cultured P. daitoensis was nearly spherical and reached up to 30 µm in diameter. Chloroplasts were arranged peripherally and often split and elongated. Cells were often vacuolated and possessed a net-like cytoplasm that resembled a football (soccer ball) in appearance, which was reflected in the genus name.

Taming chlorophylls by early eukaryotes underpinned algal interactions and the diversification of the eukaryotes on the oxygenated Earth.

Extant eukaryote ecology is primarily sustained by oxygenic photosynthesis, in which chlorophylls play essential roles. The exceptional photosensitivity of chlorophylls allows them to harvest solar energy for photosynthesis, but on the other hand, they also generate cytotoxic reactive oxygen species. A risk of such phototoxicity of the chlorophyll must become particularly prominent upon dynamic cellular interactions that potentially disrupt the mechanisms that are designed to quench photoexcited chlorophylls in the phototrophic cells. Extensive examination of a wide variety of phagotrophic, parasitic, and phototrophic microeukaryotes demonstrates that a catabolic process that converts chlorophylls into nonphotosensitive 132,173-cyclopheophorbide enols (CPEs) is phylogenetically ubiquitous among extant eukaryotes. The accumulation of CPEs is identified in phagotrophic algivores belonging to virtually all major eukaryotic assemblages with the exception of Archaeplastida, in which no algivorous species have been reported. In addition, accumulation of CPEs is revealed to be common among phototrophic microeukaryotes (i.e., microalgae) along with dismantling of their secondary chloroplasts. Thus, we infer that CPE-accumulating chlorophyll catabolism (CACC) primarily evolved among algivorous microeukaryotes to detoxify chlorophylls in an early stage of their evolution. Subsequently, it also underpinned photosynthetic endosymbiosis by securing close interactions with photosynthetic machinery containing abundant chlorophylls, which led to the acquisition of secondary chloroplasts. Our results strongly suggest that CACC, which allowed the consumption of oxygenic primary producers, ultimately permitted the successful radiation of the eukaryotes throughout and after the late Proterozoic global oxygenation.

Biochemical characterization of membrane-associated septin from rat brain.

Within the cell membrane there exist various microdomains (lipid rafts) in which specific lipids and proteins are assembled and these microdomains are recovered in the detergent-resistant low-density membrane fraction (DRM). Septin is a novel GTP-binding, cytoskeletal protein having various isoforms that assemble into homo- and heterooligomers and filaments. As the localization of septin 3 in DRM was found through a proteomics analysis of brain-derived DRM, the presence of other septin isoforms in DRM was studied. Western blotting analysis showed maturation-dependent enrichment of several septin isoforms in DRM prepared from synaptic plasma membrane (SPM). These isoforms were solubilized with high MgCl2 solution and recovered as the precipitate after dialysis to low ionic solution. Three times cycling of the extraction-dialysis process resulted in the partial purification of septin complex and electron microscopic observation of this fraction revealed rod-like structures in which building units were observed. The presence of heterooligomers was shown with western blotting after the separation of the MgCl2 extract with blue-native polyacrylamide gel electrophoresis. Immunoprecipitation assay using monoclonal anti-septin11 antibody also showed the presence of heterooligomers. These results show that septin localizes in the membrane microdomains of the SPM in adult brain and may have important roles in the membrane dynamics of neurons.

Ca(2+)- and glycoconjugates-dependent prey capture in the heliozoon Actinophrys sol.

Exocytosis of extrusomes, secretory granules found in protozoa, is involved in prey capture by the heliozoon Actinophrys sol. Here, we show that extracellular Ca(2+) is necessary for exocytosis and prey capture in A. sol. We found that A. sol could not capture prey cells in a Ca(2+)-free solution. L-type Ca(2+) channel blockers and a calmodulin antagonist also inhibited the capture of prey. These results suggest that Ca(2+) influx via L-type Ca(2+) channels plays a crucial role in exocytosis in A. sol. Concanavalin A (Con A) also inhibited prey capture, and the inhibition was relieved by the addition of its hapten sugar, alpha-mannoside, suggesting that Con A-binding glycoconjugates are implicated in exocytosis of extrusomes and the adhesion of prey cells.

Endosymbiosis-related changes in ultrastructure and chemical composition of Chlorella variabilis (Archaeplastida, Chlorophyta) cell wall in Paramecium bursaria (Ciliophora, Oligohymenophorea).

Chlorella variabilis, a symbiotic alga, is usually present in the cytoplasm of Paramecium bursaria, although it can be cultured in host-free conditions. Morphological and chemical properties of its cell wall were compared between its free-living and symbiotic states. Transmission electron microscopy (quick-freezing and freeze-substitution methods) revealed that the cell wall thickness of symbiotic C. variabilis was reduced to about half that of the free-living one. Chemical properties of the cell wall were examined by treatment with three fluorescent reagents (calcofluor white M2R, FITC-WGA, and FITC-LFA) having specific binding affinities to different polysaccharides. When the algae were re-introduced into Paramecium host cells, calcofluor fluorescence intensity reduced by about 50%. Calcofluor stains ß-d-glucopyranose polysaccharides such as cellulose, N-acetylglucosamine, sialic acid, and glycosaminoglycans. Because treatment with cellulase showed no effect on calcofluor fluorescence intensity, we consider that cellulose is not majorly responsible for the stainability of calcofluor. Staining intensities of FITC-WGA and FITC-LFA were similar in the free-living and symbiotic conditions, suggesting that N-acetylglucosamine and sialic acid are also not responsible for the reduction in the stainability of calcofluor associated with intracellular symbiosis. The amount of glycosaminoglycans on the cell wall may decrease in C. variabilis present in the cytoplasm of P. bursaria.

Bioconjugation strategy for cell surface labelling with gold nanostructures designed for highly localized pH measurement.

Regulation of intracellular pH is critically important for many cellular functions. The quantification of proton extrusion in different types of cells and physiological conditions is pivotal to fully elucidate the mechanisms of pH homeostasis. Here we show the use of gold nanoparticles (AuNP) to create a high spatial resolution sensor for measuring extracellular pH in proximity of the cell membrane. We test the sensor on HepG2 liver cancer cells and MKN28 gastric cancer cells before and after inhibition of Na+/H+ exchanger. The gold surface conjugation strategy is conceived with a twofold purpose: i) to anchor the AuNP to the membrane proteins and ii) to quantify the local pH from AuNP using surface enhanced Raman spectroscopy (SERS). The nanometer size of the cell membrane anchored sensor and the use of SERS enable us to visualize highly localized variation of pH induced by H+ extrusion, which is particularly upregulated in cancer cells.

Putative Neural Network Within an Olfactory Sensory Unit for Nestmate and Non-nestmate Discrimination in the Japanese Carpenter Ant: The Ultra-structures and Mathematical Simulation.

Ants are known to use a colony-specific blend of cuticular hydrocarbons (CHCs) as a pheromone to discriminate between nestmates and non-nestmates and the CHCs were sensed in the basiconic type of antennal sensilla (S. basiconica). To investigate the functional design of this type of antennal sensilla, we observed the ultra-structures at 2D and 3D in the Japanese carpenter ant, Camponotus japonicus, using a serial block-face scanning electron microscope (SBF-SEM), and conventional and high-voltage transmission electron microscopes. Based on the serial images of 352 cross sections of SBF-SEM, we reconstructed a 3D model of the sensillum revealing that each S. basiconica houses > 100 unbranched dendritic processes, which extend from the same number of olfactory receptor neurons (ORNs). The dendritic processes had characteristic beaded-structures and formed a twisted bundle within the sensillum. At the "beads," the cell membranes of the processes were closely adjacent in the interdigitated profiles, suggesting functional interactions via gap junctions (GJs). Immunohistochemistry with anti-innexin (invertebrate GJ protein) antisera revealed positive labeling in the antennae of C. japonicus. Innexin 3, one of the five antennal innexin subtypes, was detected as a dotted signal within the S. basiconica as a sensory organ for nestmate recognition. These morphological results suggest that ORNs form an electrical network via GJs between dendritic processes. We were unable to functionally certify the electric connections in an olfactory sensory unit comprising such multiple ORNs; however, with the aid of simulation of a mathematical model, we examined the putative function of this novel chemosensory information network, which possibly contributes to the distinct discrimination of colony-specific blends of CHCs or other odor detection.