The expression pattern of four odorant-binding proteins in male and female silk moths, Bombyx mori

Four recombinant odorant-binding proteins of Bombyx mori, pheromone-binding protein (PBP), general odorant-binding protein 1 (GOBP1), general odorant-binding protein 2 (GOBP2) and antennal binding protein X (ABPX), were expressed in E. coli and used to raise polyclonal antisera. Immunoblots of antennal homogenates showed that these antisera were specific. In Western blot analysis and immunocytochemical labelling experiments, the sera against recombinant PBP and GOBP2 of B. mori gave identical results as sera against native PBP and GOBP2 of Antheraea polyphemus, respectively, thus confirming earlier results obtained with the latter. Labelling consecutive cross sections of various sensillum types with all four antisera revealed different labelling patterns in male and female sensilla (s.) trichodea and s. basiconica. Long s. trichodea in males and females represented uniform labelling types, whereas for short s. trichodea, s. intermedia, and s. basiconica a great variety of labelling patterns was observed, some being more common than others. Long s. trichodea, which in males are uniformly tuned to the pheromone components bombykol and bombykal, all strongly expressed PBP; labelling with antisera against the other three odorant-binding proteins hardly was above background, only in some hairs GOBP1 was expressed somewhat more strongly. Long s. trichodea of females, which respond specifically to linalool and benzoic acid, showed a different labelling pattern. Here, we observed strong labelling with antibodies against GOBP2 and medium labelling with anti-GOBP1, sometimes with anti-ABPX. S. basiconica in both sexes most commonly co-expressed GOBP1 and GOBP2, but other patterns were occasionally found, with some of them showing PBP expression, also in females. The great variety of labelling types in short s. trichodea, s. intermedia, and s. basiconica suggests a similar variety of functional subtypes as observed in plant odour-sensitive sensilla of other moth species.     

Immunolocalization of odorant-binding proteins in noctuid moths (Insecta, Lepidoptera)

Odorant-binding proteins were studied in the noctuid moths Agrotis segetum, Autographa gamma, Helicoverpa armigera, Heliothis virescens and Spodoptera littoralis using antisera raised against the pheromone-binding protein (PBP) and general odorant-binding protein 2 (GOBP2) of Antheraea polyphemus (Saturniidae). Proteins immunoreacting with these antisera were only found on the antennae and PBP and GOBP2 could be identified on western blots of males and females of all five species. PBPs were predominantly localized in sensilla trichodea and GOBP2 in sensilla basiconica, in good correlation with the stimulus specificity of the receptor cells in these sensilla. In H. armigera and H. virescens the majority of the s. trichodea immunoreacted with the antiserum against PBP of A. polyphemus; in A. segetum, A. gamma and S. littoralis, on the other hand, a high percentage of s. trichodea remained unlabelled. Probably, the PBP expressed in these sensilla is so different that it does not immunoreact with the antiserum used. Such a protein was found by native PAGE of antennal extracts of A. segetum and S. littoralis. These data correlate with the fact that the two heliothine species use pheromones with the same alkyl chain length as A. polyphemus, while the other three species use pheromones with shorter chains. In H. armigera, H. virescens, A. gamma and S. littoralis female antennae were also immunolabelled and a large number of PBP-expressing s. trichodea was consistently found. In S.littoralis this fits with the electrophysiologically recorded high pheromone sensitivity of female s. trichodea, whereas in females of H. armigera and H. virescens no or only weak responses to pheromone stimulation have been reported. Therefore, PBP expression in a sensillum does not necessarily imply pheromone sensitivity of its receptor cells.     

Immunolocalization of general odorant-binding protein in antennal sensilla of moth caterpillars

Antennae of Bombyx mori and Helicoverpa armigera larvae were immunolabelled with antisera raised against the pheromone-binding protein or the general odorant-binding protein 2 of Antheraea polyphemus to assign the expression of these proteins to individual sensilla and to compare the localization pattern with that in sensilla of adult moths. Specific labelling of antennal sensilla was only obtained with the antiserum against general odorant-binding protein 2. Among the few sensilla present on the antenna the three large sensilla basiconica, which are suspected to be olfactory in function, were labelled. These sensilla are compound sensilla consisting of several sensillum units which form a common sensory hair. The hair is single-walled and pierced by many pores. Labelling of sensillum compartments was the same as in sensilla of adults. Prominent labelling of the sensillum lymph is accompanied by labelling of secretory organelles in the two outermost auxiliary cells and of endocytotic pathways in all sensillum cells. The results suggest that general odorant-binding protein is expressed in single-walled multiporous sensilla of presumed olfactory function on the antenna of moth larvae. The overall identity of the localization pattern for general odorant-binding protein between larval and adult sensilla implies a similar role of these proteins in olfactory stimulus transduction.     

Immunocytochemical localization of pheromone-binding protein in moth antennae

Summary Odorant-binding proteins are supposed to play an important role in stimulus transport and/or inactivation in olfactory sense organs. In an attempt to precisely localize pheromone-binding protein in the antenna of moths, post-embedding immunocytochemistry was performed using an antiserum against purified pheromone-binding protein of Antheraea polyphemus. In immunoblots of antennal homogenates, the antiserum reacted exclusively with pheromone-binding protein of A. polyphemus, and cross-reacted with homologous proteins of Bombyx mori and Autographa gamma. On sections of antennae of male A. polyphemus and B. mori, exclusively the pheromone-sensitive sensilla trichodea are labelled; in A. gamma, label is restricted to a subpopulation of morphologically similar sensilla trichodea, which indicates that not all pheromone-sensitive sensilla contain the same type of pheromone-binding protein and accounts for a higher specificity of pheromone-binding protein than hitherto assumed. Within the sensilla trichodea, the extracellular sensillum lymph of the hair lumen and of the sensillum-lymph cavities is heavily labelled. Intracellular label is mainly found in the trichogen and tormogen cells: in endoplasmic reticulum, Golgi apparatus, and a variety of dense granules. Endocytotic pits and vesicles, multivesicular bodies and lysosome-like structures are also labelled and can be observed not only in these cells, but also in the thcogen cell and in the receptor cells. Cell membranes are not labelled except the border between thecogen cell and receptor cell and the autojunction of the thecogen cell. The intracellular distribution of label indicates that pheromone-binding protein is synthesized in the tormogen and trichogen cell along typical pathways of protein secretion, whereas its turnover and decomposition does not appear to be restricted to these cells but may also occur in the thecogen and receptor cells. The immunocytochemical findings are discussed with respect to current concepts of the function of pheromone-binding protein.     

Expression patterns of odorant-binding proteins in antennae of the moth<Emphasis Type="Italic"> Manduca sexta</Emphasis>

Monoclonal antibodies (MAbs) were generated to six recombinant proteins (odorant-binding proteins; OBPs) of Manduca sexta. The specificity of each MAb was demonstrated by labeling six immunoblots, each of which contained samples of all six recombinant OBPs. The expression patterns of the six OBPs could be grouped into three classes: (1) one (GOBP1) was expressed in sensilla located throughout each annulus; (2) two (ABPX and ABP2) were expressed in the long sensilla trichoidea bordering a zone that was arranged as an arch on the periphery of each annulus; (3) three (PBP2, PBP3, and GOBP2) were expressed in shorter sensilla occupying a wedge-shaped mid-annular zone of each annulus. In female antennae, sensilla expressing these OBPs were intermixed, and the distinct zonation observed in the male antenna was absent. In males, PBP2 was co-expressed in exactly the same cells of the mid-annular zone as those expressing PBP3 and most of the same cells expressing GOBP2, although its expression overlapped with no or only a few sensilla expressing OBPs of class 1 (GOBP1) or class 2 (ABPX, ABP2). This overlap of expression or lack of overlap between PBP2 and the other OBPs for male antennae was mirrored in female antennae. In view of the restricted spatial expression of OBPs within an annulus and the diversity of possible dimeric combinations of OBPs that arises from the co-expression of multiple OBPs in a given sensillum, OBPs could contribute to the specificity of the olfactory responses of insects.This research was supported by grants from the National Science Foundation (IBN-9604095) and the University of Illinois Critical Research Initiatives     

Molecular cloning and bacterial expression of pheromone binding protein in the antennae of Helicoverpa armigera (Hübner)

A cDNA clone coding for pheromone binding protein was isolated from the antennae of Helicoverpa armigera by RT-PCR and (5'/3')-RACE technique. The full-length of H. armigera pheromone binding protein (HarmPBP) was 952 bp, possessing 162 amino acid residues including a signal peptide of 20 amino acids. Its predicted molecular weight and isoelectric point were 18.26 kDa and 5.23, respectively. This deduced amino acid sequence shared some common structural features with odorant-binding proteins from several moth species, including the six conserved cysteine motif, a typical characteristic of insect's odorant-binding proteins. Northern blot showed that HarmPBP is specifically expressed in the antennae of Helicoverpa armigera and more abundantly expressed in male than female. During the antennal development, HarmPBP is first expressed about 4 days prior to adult eclosion and rises to a plateau 2 days prior to adult eclosion. In order to obtain sufficient PBP for further determining its biochemical and physiological properties, a bacterical expression vector of PBP was constructed and successfully expressed in Escherichia coli. The recombinant PBP was shown to cross-react with an anti-PBP antiserum from Antheraea polyphemus. Polyclonal antibodies against HarmPBP were used to mark the distribution of the protein in olfactory sensilla. Very strong labeling was observed in the sensillum lymph of the hair lumen and of the sensillum-lymph cavity. In the male, HarmPBP is expressed in sensilla trichodea and not in sensilla basiconica, while in the female, it is expressed both in sensilla basiconica and sensilla trichodea.     

The antennae of neopseustid moths: Morphology and phylogenetic implications, with special reference to the sensilla (Insecta, Lepidoptera, Neopseustidae)

The antennae of Lepidoptera Neopseustidae were examined with the scanning electron microscope. The studied species, Nematocentropus cfr. omeiensis, Neopseustis meyricki, Synempora andesae, Apoplania valdiviana and Apoplania penai possess nine types of antennal flagellum sensilla: multiporous large sensilla basiconica, multiporous thin sensilla basiconica, multiporous small sensilla basiconica, multiporous sensilla trichodea, multiporous sensilla coeloconica; uniporous sensilla chaetica; aporous sensilla chaetica, aporous stylus-shaped sensilla chaetica, aporous sensilla styloconica.The multiporous sensillum type here termed “multiporous large sensillum basiconicum” is unknown from other Lepidoptera and probably constitutes an autapomorphy of the family Neopseustidae. This sensillum type is remarkable by having a single base in female Apoplania and Synempora while in male Apoplania it has a bifid or trifid base, and in male Synempora it is composed of two or three incompletely separated hairs. This may be the first recorded example of a sexually dimorphic lepidopteran sensillum type. The stylus-shaped sensillum chaeticum is a primitive type which occurs only in some lower Lepidoptera.     

Expression of odorant-binding and chemosensory proteins and spatial map of chemosensilla on labial palps of Locusta migratoria (Orthoptera: Acrididae)

The sensilla on labial palps in Locusta migratoria were observed and mapped using light microscopy, scanning and transmission electron microscopy. A dome region on the tip of the fourth segment (distal segment) of labial palps is mainly covered with sensilla chaetica (about 98%), and few sensilla basiconica (2%). The total number of both types of sensilla is significantly higher in females than in males. Sensilla chaetica can be further subdivided into three groups containing 6, 7 or 10 neurons. Immunocytochemical localization of odorant-binding protein (OBP) and chemosensory proteins (CSPs) was performed on ultrathin sections of sensilla on labial palps. The antiserum against odorant-binding protein from Locusta migratoria (LmigOBP) only labelled sensilla basiconica, with gold granules only found in the sensillum lymph. Chemosensory protein instead was specifically present in the outer sensillum lymph of all three subgroups of sensilla chaetica with antiserum against CSP-I from Schistocerca gregaria (SgreCSP-I). In contrast these three subgroups were never labelled with antiserum against CSP-II from Locusta migratoria (LmigCSP-II). In addition, a few sensilla chaetica could not be stained with any of the antisera used.     

Sexual dimorphism in neuronal projections from the antennae of silk moths (Bombyx mori,Antheraea polyphemus) and the gypsy moth (Lymantria dispar)

Summary The antennal lobe of both sexes of the silk moth Bombyx mori contains 55–60 ventrally located antennal glomeruli; in addition, that of the male contains a dorsal macroglomerular complex (MGC). A group of identifiable glomeruli consisting of two lateral large glomeruli (LLG) and four medial small glomeruli (MSG) is present in both sexes, but the LLG are greatly enlarged in the female. A MGC is also present in the male gypsy moth Lymantria dispar and male giant silk moth Antheraea polyphemus. The MGC in all of these species is organized into 3–4 distinct levels of glomeruli. Antennal sensory fibers were stained by cobalt backfills in B. mori, A. polyphemus, and L. dispar. Most fibers stained from cut long hairs (sensilla trichodea) projected to MGC in males and LLG in both sexes of B. mori. The distribution of fibers in the MGC of B. mori was topographically biased in that a majority of fibers from anterior branches projected medially in MGC while most fibers from posterior branches projected laterally or anteriorly. Terminal arborizations of single fibers were each restricted to a single glomerular level of the MGC. Fibers projecting to the posterior antennal center were frequently stained in cut-hair and control preparations, apparently by uptake of cobalt through intact sensilla on flagellar branches.     

The fine structure of thermo-/hygrosensitive sensilla in the silkmoth Bombyx mori: Receptor membrane substructure and sensory cell contacts

Summary The thermo-/hygroreceptive sensilla styloconica of the silkmoth Bombyx mori are located on the tips of the antennal branches. A small poreless cuticular peg is innervated by three sensory cells. The outer dendritic segments of two type-1 receptor cells, the presumed hygroreceptors, almost completely fill the peg lumen and are in close contact with each other. The outer dendritic segment of the third (type-2) receptor cell, the presumed thermoreceptor, forms lamellae below the peg base. The membranes of these lamellae are studded with knobs in orthogonal array, protruding into the extracellular space with the same orientation on facing lamellae. This Bossy Orthogonal Surface Substructure (BOSS) is assumed to play a role in thermoreceptor function. Contacts are observed between the outer dendritic segments, between the inner dendritic segments immediately below the ciliary segments, and between the sensory cell somata. These contacts, which are not found in the olfactory sensilla (s. trichodea and basiconica) of this species, indicate electrical interactions between the three sensory cells of the styloconic sensillum and possibly are involved in the antagonistic and/or bimodal response characteristics of thermo-/hygroreceptor cells.     

红火蚁触角及其上感受器的扫描电镜观察

应用扫描电镜对采自我国广东吴川和广西南宁的红火蚁Solenopsis invicta Buren工蚁、有翅雌蚁和雄蚁触角的形态和感受器类型进行了研究。结果表明,工蚁、雌蚁和雄蚁的触角存在着较大的差异。工蚁和雌蚁的触角为膝状,末端2或3节膨大为棒状,雌蚁的触角11节,比工蚁(10节)的多1节。雄蚁的触角为线状,12节,末端没有棒状结构。工蚁和雌蚁的触角上共有7种感受器,分别为毛形、曲毛形、锥形、腔锥形、坛形、刺形感受器和Böhm氏鬃毛,前6种感受器大多集中在触角末端的棒节,棒节以外的各鞭节上主要是毛形感受器,Böhm氏鬃毛则分布于柄节和梗节的基部,鞭节上无此感受器。雄蚁触角上也有7种感受器,但其分布与工蚁的有较大差异,Böhm氏鬃毛的分布与工蚁和雌蚁的相同,锥形感受器分布在末端2节,坛形感受器分布在末端3节,其余的4种感受器较为均匀地分布在各鞭节,而不是聚集在端节。另外,新发现雄蚁中存在一种与已知的毛型感受器不同的超短毛状感受器,定名为超短毛感受器。最后,对红火蚁的触角及感受器在蚁群社会性行为中的作用进行了讨论。     

Cloning,expression and immunocytochemical localization of a general odorant-binding protein gene from Helicoverpa armigera (Hübner)

A cDNA clone coding for general odorant-binding protein2 was isolated from the antenna of Helicoverpa armigera by RT-PCR and (5'/3')-RACE technique. Results of sequencing and structural analyses showed that the full-length of GOBP2Harm was 636 bp, possessing 162 amino acid residues and a signal peptide of 21 amino acids. Its predicted molecular weight and isoelectric point were 18.2 kDa and 5.21, respectively. This deduced amino acid sequence shared some common structural features with odorant-binding proteins from several moth species, including the six conserved cysteine motif, typical of insect's OBPs. Northern blot showed that GOBP2Harm is specifically expressed in the antenna of Helicoverpa armigera at similar levels in both sexes. In order to obtain sufficient GOBP2 for further determining its biochemical and physiological properties, a bacterical expression vector of GOBP2 was constructed and successfully expressed. The protein was obtained mainly as insoluble inclusion bodies, that, however, could be solubilized and refolded. The rGOBP2 was purified by affinity chromatography and gel filtration. The rGOBP2 was shown to cross-react with an anti-GOBP antiserum from Antheraea polyphemus. Finally, polyclonal antibodies against GOBP2Harm were used to mark the distribution of the protein in olfactory sensilla and were tested by immuno-electron microscopy. In the male, GOBP2Harm is mainly expressed in sensilla basiconica, while in the female, it is equally expressed in sensilla basiconica and in sensilla trichodea.     

Pheromone‐binding proteins in the Asian gypsy moth females,Lymantria dispar,recognizing the sex pheromone and plant volatiles

Lepidopterans are known to have different pheromone‐binding proteins with differential expression patterns that facilitate specific signal transduction of semiochemicals. Two PBPs of the Asian gypsy moth, Lymantria dispar, were reported to express in both females and males, but their physiological functions were unknown. Results showed that LdisPBP1 and LdisPBP2 were expressed in the sensilla trichodea of males and the s. trichodea and s. basiconica of females. When LdisPBP1 gene was targeted by RNA interference (RNAi) in males, the expression of LdisPBP1 and LdisPBP2 decreased by 69 and 76%, respectively, and when LdisPBP2 gene was targeted by RNAi, they decreased by 60 and 42%, respectively. In females, after treatment with LdisPBP1 dsRNA, LdisPBP1 and LdisPBP2 levels were reduced by 26 and 69%, respectively, and LdisPBP2 dsRNA reduced the relative expression of them by 4 and 62%, respectively. The expression of LdisPBP1 and LdisPBP2 was interdependent. Electroantennogram (EAG) recordings showed that LdisPBPs participate in the recognition of the sex pheromone in males, and the sex pheromone and plant volatiles in females. The function of LdisPBPs represents the sex‐specific roles.     

Candidate pheromone binding proteins of the silkmoth Bombyx mori

Pheromone reception is thought to be mediated by pheromone binding proteins (PBPs) in the aqueous lymph of the antennal sensilla. Recent studies have shown that the only known PBP of Bombyx mori (BmorPBP1) appears to be specifically tuned to bombykol but not to bombykal, raising the question of whether additional subtypes may exist. We have identified two novel genes, which encode candidate PBPs (BmorPBP2, BmorPBP3). Comparison with PBPs from various moth species have revealed a high degree of sequence identity and the three BmorPBP-subtypes can be assigned to distinct groups within the moth PBP family. In situ hybridization revealed that BmorPBP2 and BmorPBP3 are expressed only in relatively few cells compared to the number of cells expressing BmorPBP1. Double-labeling experiments have shown that the two novel BmorPBPs are expressed in the same cells but are not co-expressed with BmorPBP1. Furthermore, unlike BmorPBP1, cells expressing the newly identified PBPs did not surround neurons containing the BmOR-1 receptor. The results indicate that BmorPBP2 and BmorPBP3 are located in sensilla types, which are different from the long sensilla trichodea.Data deposition: The sequences reported in this paper have been deposited in the EMBL database under accession nos. AM403100 (BmorPBP2) and AM403101 (BmorPBP3).     

Morphology and distribution of sensilia on the cephalic appendages,tarsi and ovipositor of the European sunflower moth,Homoeosoma nebulella Den. & Schiff. (Lepidoptera : Pyralidae)

Sensilla on male and female antennae, mouthparts, tarsi and on the ovipositor of the European sunflower moth, Homoeosoma nebulella (Lepidoptera : Pyralidae) have been investigated by means of scanning electron microscope. The antennal flagellum bears multiporous sensilla (trichodea, basiconica, auricillica, coeloconica) and uniporous sensilla (chaetica, styloconica). A sexual dimorphism is found in the numbers of sensilla trichodea (8300 in males and 6000 in females) and sensilla basiconica (1150 in females and 650 in males). The proboscis has uniporous s. styloconica, multiporous s. basiconica (described for the first time in Lepidoptera), aporous s. chaetica, and some rare uniporous s. basiconica in the food channel. The labial palp-pit organ houses multiporous s. coeloconica, while the maxillary palps have aporous sensilla. Tarsi of both sexes possess one type of aporous s. chaetica and 2 types of uniporous s. chaetica. There is no significant difference in the distribution of tarsal sensilla between males and females. The surface of each lobe of the ovipositor is covered by 3 types of aporous s. trichodea of different lengths and about 60 multiporous s. basiconica, sensilla unusual on the ovipositor of Lepidoptera. The role of sensilla in the oviposition site selection is discussed.     

Description of the antennal sensilla of <Emphasis Type="Italic">Habrobracon Hebetor</Emphasis>

The morphology of the antennal sensilla of both male and female Habrobracon hebetor (Say) (Hymenoptera: Braconidae) is described using Scanning Electron Microscopy complemented with Transmission Electron Microscopy. Five types of innervated sensilla as well as uninnervated microtrichia were found. These types are: sensilla trichodea; s. chaetica; s. basiconica; s. coeloconica; and s. placodea. No differences in shape, basic structure, and types of antennal sensilla were found between males and females. The types of sensilla of both sexes of H. hebetor were compared with what has been described in other parasitic Hymenoptera, and their putative functions are discussed with reference to their morphology, distribution and ultrastructure.     

分月扇舟蛾触角感觉器的扫描电镜观察

利用扫描电镜对分月扇舟蛾Clostera anastomosis(L.)成虫触角感觉器的形态、结构进行了观察。扫描电镜观察结果表明,分月扇舟蛾触角由柄节、梗节和鞭节组成,触角外侧面覆盖有鳞片,绝大部分触角感觉器位于触角的腹面和外侧面。雌、雄蛾触角上均存在以下8种感觉器,即毛形感器、刺形感器、腔形感器、腔锥形感器、栓锥形感器、锥形感器、柱形感器和鳞形感器。各种感觉器在雌、雄蛾触角上的分布大体相同,但数量有明显的区别。     

Pheromone-binding proteins contribute to the activation of olfactory receptor neurons in the silkmoths antheraea polyphemus and Bombyx mori

The sensilla trichodea of the silkmoth Antheraea polyphemus are innervated by three types of receptor neurons each responding specifically to one of three pheromone components. The sensillum lymph of these sensilla surrounding the sensory dendrites contains three different types of pheromone-binding proteins (PBPs) in high concentrations. The sensilla trichodea of the silkmoth Bombyx mori are supplied by two receptor neurons each tuned specifically to one of the two pheromone components bombykol and bombykal, but only one type of PBP has been found so far in these sensilla. Recombinant PBPs of both silkmoth species in various combinations with pheromone components were applied to the receptor neurons via tip-opened sensilla during electrophysiological recordings. Over a fairly broad range of pheromone concentrations the responses of the receptor neurons depended on both, the pheromone component and the type of the PBP. Therefore, the PBPs appear to contribute to the excitation of the receptor neurons. Furthermore, bombykal in combination with the expressed PBP of B. mori failed to activate the corresponding receptor neuron of B. mori, but did so if combined with one of the PBPs of A. polyphemus. Therefore, a still unknown binding protein involved in bombykal transport might be present in B. mori.     

Der Feinbau olfaktorischer Sensillen des Seidenspinners (Insecta,Lepidoptera)

Zusammenfassung Die Sensilla (S.) trichodea und S. basiconica auf den Antennen des Seidenspinners,Bombyx mori, wurden nach chemischer Fixierung, Gefriersubstitution und Gefrierätzung im Transmissionselektronenmikroskop untersucht. Es lassen sich fünf Typen von Sensillen unterscheiden, deren olfaktorische Funktion aus elektrophysiologischen Versuchen bekannt ist, mit Ausnahme des letzten Typs.Lange S. trichodea undhalblange S. trichodea I sind jeweils von zwei Sinneszellen innerviert, deren Rezeptorfortsätze (Dendriten) im wesentlichen unverzweigt bleiben. Diegroßen S. basiconica haben meist drei, diekleinen S. basiconica nur eine Sinneszelle; die Dendriten dieser Rezeptorzellen verzweigen sich büschelförmig beim Eintritt in das Haarlumen. Erstmals wird ein Zwischentyp beschrieben: diehalblangen S. trichodea II ähneln hinsichtlich der Innervation den S. basiconica, sind aber wegen der Form und Größe des Sinneshaars als S. trichodea zu klassifizieren. Für jeden Typ werden die Abmessungen der Rezeptorfortsätze sowie die Zahl und Verteilung der reizleitenden Poren und Porentubuli in der Haarwand angegeben.Auf der männlichen Antenne sind die langen S. trichodea am zahlreichsten; sie enthalten hochempfindliche Sexuallockstoffrezeptoren (mittlere Anzahl pro Antenne: 17 000 Sensillen mit 34 000 Sinneszellen). Beim Weibchen sind diese Sensillen in der Zahl auf etwa 35% reduziert und mit Sinneszellen anderer Spezifität und geringerer Empfindlichkeit ausgerüstet. Die beiden Dendriten der langen S. trichodea unterscheiden sich bei beiden Geschlechtern stark im mittleren Durchmesser und der Anzahl der cytoplasmatischen Mikrotubuli; beim Männchen reichen beide bis zur Haarspitze, beim Weibchen endet der dünnere Fortsatz bereits im proximalen Haardrittel. Die Cuticula der Sinneshaare ist von Poren durchbrochen (: 2–7 Poren/²; : 2–5 Poren/²), die stets in der Nähe von charakteristischen Stufen in der Haaroberfläche münden. Jeder Porenkanal führt in ca. fünf Porentubuli, die bis ins Haarlumen reichen und dort enden, zum Teil in Kontakt mit der Rezeptormembran der Dendriten. Die Häufigkeit solcher Tubulus-Membrankontakte ist in distalen Haarabschnitten größer als in proximalen. Der dickere Dendrit weist etwa viermal so viel Kontakte auf wie der dünnere. Die beiden Rezeptorzellen dieser Sensillen stellen funktionell verschiedene Reaktionstypen dar, was mit den beobachteten morphologischen Unterschieden zusam menhängen dürfte.Die S. basiconica haben 20 Poren pro ² ihrer Oberfläche und 12–23 Porentubuli pro Pore; dadurch erreichen oder übertreffen sie die viel größeren S. trichodea in der Gesamtzahl der Porentubuli pro Sinneshaar. Auf den S. trichodea steigt die Zahl der Poren pro Oberflächeneinheit zur Spitze hin stetig an, während die Zahl der Poren pro Haarlängeneinheit einen konstanten Wert annimmt. Eine Hypothese über die Morphogenese dieser Verteilung wird aufgestellt.Die funktionelle Bedeutung der äußeren Epicuticulaschichten und der Porentubulussysteme für die Reizleitung wird diskutiert. Ausgehend von beliebigen Orten ihres Auftreffens auf dem Sinneshaar können die Duftmoleküle zunächst durch zweidimensionale Diffusion entlang der Haaroberfläche zu den Poren gelangen und anschließend durch eindimensionale Diffusion über Porenkanäle und Porentubuli die Rezeptormembran erreichen. Die berechneten Diffusionszeiten sind kürzer als die bekannten Rezeptorlatenzen; die Reizleitung kann also durch Diffusion hinreichend erklärt werden und erfordert keine kompliziertere Hypothese.

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The fine structure of olfactory sensilla in the silk moth (insecta, lepidoptera)

Summary The sensilla (s). trichodea and s. basiconica on the antennae of the silk moth,Bombyx mori, were studied under the transmission electron microscope. Chemical fixation, freeze substitution and freeze etching methods were used. The following results have been obtained: Five sensillum types were distinguished, the olfactory function of which is known from electrophysiological recordings, except for the last one. Thelong s. trichodea and themedium-sized s. trichodea I are innervated by two sensory cells which have essentially unbranched receptor processes (dendrites). Commonly thelarge s. basiconica contain three sensory cells, thesmall s. basiconica only one; the dendrite of these receptor cells branch multiply when entering the hair lumen. For the first time an intermediate type has been described: themedium-sized s. trichodea II, which resemble the s. basiconica in their branching innervation, but must be classified as s. trichodea because of the form and size of the sense hair. For each type, the dimensions of the receptor processes, as well as the number and distribution of the stimulus conducting pores and pore tubules in the hair wall are noted.On the male antenna the long s. trichodea are most abundant; they contain the highly sensitive sex pheromone receptors (mean number per antenna: 17 000 sensilla with 34 000 sense cells). In the female these sensilla are reduced in number to about 35% and supplied with receptor cells of different specificity and lower sensitivity. In both sexes, the two dendrites of the long s. trichodea differ markedly in their mean diameter, and the number of cytoplasmatic microtubules. In the male moth both receptor processes reach the hair tip, whereas in the female the thinner one invades only the proximal third of the sense hair. The cuticle of the hair wall is perforated by pores (: 2–7 pores per ²; : 2–5 pores per ²), which mostly open to the outside near to characteristic steps in the hair surface. Each pore canal leads into about five pore tubules, which proceed towards the hair lumen, where they end, partly in contact with the receptor membrane of the dendrites. Distal parts of the sense hairs show such tubule-membrane contacts more frequently than proximal regions. The number of contacts counted on the thicker dendrite is about four times greater than on the thinner one. In these sensilla, the two receptor cells constitute functionally different reaction types, which may relate to the observed morphological differences.The s. basiconica have about 20 pores per ² of the hair surface, and 12–23 pore tubules per pore: thus, these sensilla have the same or even a greater number of pore tubules per sensillum than the much larger s. trichodea. In the s. trichodea the number of pores per unit surface increases steadily towars the hair tip, while the number of pores per unit length of the hairs soon reaches a constant value. A hypothesis about the morphogenesis of this distribution is given.The functional significance of the epicuticular surface layers and of the pore tubule systems is discussed under the aspect of stimulus conduction. Starting from the site of impact anywhere on the sense hair, odour molecules may diffuse two-dimensionally along the hair surface to the pores, and then proceed by one-dimensional diffusion through pore canals and pore tubules until they eventually reach the receptor membrane at the end of a tubule. The calculated conduction times are shorter than the known receptor latencies; thus, the transport mechanism can be explained by diffusion and does not need a more complex hypothesis.

Ich danke Frl. B. Müller für ihre stete, sorgfältige Hilfe, Prof. L. Bachmann und Dr. W. Schmitt von der TU München für die Benützungsmöglichkeit der Gefrierätzanlage und ihren erfahrenen Rat, Dr. G. Adam von der Universität Konstanz sowie meinen Seewiesener Kollegen, Dr. W. A. Kafka, Dr. K.-E. Kaissling und Dr. E. Priesner, für viele anregende Diskussionen und konstruktive Kritik.     

Heterogeneity of Odorant-binding Proteins in the Antennae of Bombyx mori

Different odorant-binding proteins (OBPs) were isolated fromtotal antennal homogenates of male and female Bombyx mori. Proteinswere separated according to their isoelectric point by usingpreparative fast-flow isoelectrofocusing. Odorant-binding proteinswere identified in immunoblots by antisera raised against thepheromone-binding protein (anti-PBP) and the general odorant-bindingprotein (anti-GOBP2) of Antheraea polyphemus. Four proteinscross-reacting with anti-PBP were detected in males and twoin females, while three proteins cross-reacting with anti-GOBP2were found in males and five in females. Both anti-PBP and anti-GOBP2cross-reacting proteins had an apparent molecular weight of15–16 kDa. In parallel, the same two antisera were usedin immunocytochemical studies in order to determine the distributionof these proteins within the various subtypes of olfactory sensilla.The presence of multiple odorant-binding proteins within onemoth species as well as their complex distribution pattern supportthe suggestion that soluble OBPs might have a function in odorantdiscrimination. Chem. Senses 22: 503–515, 1997.