金龟子化学通讯与信息化学物质

本文综述了金龟子的化学通讯与信息化学物质研究与应用的新进展,重点评述了丽金龟科和鳃金龟科性信息素的鉴定与化学结构。迄今,已有14种金龟子的性信息素被鉴定,还有一些金龟子的聚集信息素和两性引诱剂被报道。对金龟子性信息素、聚集信息素和引诱剂等信息化学物质的应用也作了概述。     

Three pheromone-binding proteins help segregation between two Helicoverpa species utilizing the same pheromone components

The two sibling species Helicoverpa armigera and Helicoverpa assulta utilise the same two aldehydes as their sex pheromones, but in opposite ratios. In both species three odorant-binding proteins (OBPs) can be classified as pheromone-binding proteins (PBPs). To investigate the role of these three PBPs in chemical communication between sexes and their mode of action, we have expressed the proteins in bacteria and prepared mutants lacking their C-terminal regions. Using polyclonal antibodies we found that the expression of the three PBPs is basically confined to the antennae of both sexes and both species. Binding experiments with the fluorescent probe N-phenyl-1-naphthylamine across a pH range indicated that, the affinity of wild-type proteins decreases at low pH, while that of the mutants is not or less affected, suggesting that a conformational change of the C-terminus occurs in these proteins, as reported for other lepidopteran OBPs. All three proteins bind with similar strength both pheromone components, as well as their corresponding alcohols and acetates. However, they exhibit significant selectivity to linear alcohols and aldehydes of different length, with optimal affinities to the ligand of 13-15 carbon atoms for PBP1 and 12-14 carbon atoms for PBP2. We suggest that all three PBPs might cooperate to build a unique olfactory image, that could help avoiding cross-mating between the two species and with other noctuids.     

Factors affecting pheromone production in beetles

Pheromone production and/or release by beetles is coordinated with a variety of behavioral, physiological, and environmental factors. To data, two basic mechanisms for the regulation of pheromone biosynthesis in beetles have been proposed. Pheromone biosynthesis may simply be dependent on the availability of biosynthetic precursors. Alternatively, certain stimuli or events may trigger pheromone biosynthesis via juvenile hormone (JH) action. JH may either act directly at the site of pheromone biosynthesis to enhance pheromone production or may act indirectly, through a brain hormone (which might be related to the pheromone biosynthesis activating neuropeptide) or through effects on antennal sensory response. Knowledge of the regulation of the initiation and termination of pheromone biosynthesis is reviewed. Mechanisms by which pheromone stereochemistry is controlled are also discussed. This is an important aspect of pheromone production in Coleoptera, since slight changes in the stereochemistry can completely alter the activity of the molecule. © 1994 Wiley-Liss, Inc.     

Use of habitat resources by scarab dung beetles in an savanna

In the Queen Elizabeth National Park, Uganda, we compared the scarab beetle assemblages in the dung of three wild ungulates (African buffalo, a ruminant foregut fermenter; hippopotamus, nonruminant foregut fermenter; and warthog, nonruminant hindgut fermenter). Dung was collected from two sandy-clay soils with different percentage of coarse sand. We aimed at investigating habitat resource selection by dung beetle species within a savanna natural contest with abundant and diverse food availability. Analyses were performed to detect differences for dung beetle assemblages in abundance, diversity, functional groups. Species richness in the three dung types and in the two soil types was similar. However, warthog dung and sandy-rich soil appeared the preferred habitat resources, in terms of abundance and biomass, while hippopotamus dung hosted the lowest values for these parameters. The analysis of functional groups revealed that slow-burying tunnellers held the major role, both in terms of abundance and biomass, and were mainly found in warthog dung.     

Molecular switches for pheromone release from a moth pheromone-binding protein

Pheromone-binding proteins (PBPs) are involved in the uptake of pheromones from pores on the antennae, transport through an aqueous environment surrounding the olfactory receptor neurons, and fast delivery to pheromone receptors. We tested the hypothesis that a C-terminal segment and a flexible loop are involved in the release of pheromones to membrane-bound receptors. We expressed in Escherichia coli 11 mutants of the PBP from the silkworm moth, BmorPBP, taking into consideration structural differences between the forms with high and low binding affinity. The N-terminus was truncated and His-69, His-70 and His-95 at the base of a flexible loop, and a cluster of acidic residues at the C-terminus were mutated. Binding assays and circular dichroism analyses support a mechanism involving protonation of acidic residues Asp-132 and Glu-141 at the C-terminus and histidines, His-70 and His-95, in the base of a loop covering the binding pocket. The former leads to the formation of a new α-helix, which competes with pheromone for the binding pocket, whereas positive charge repulsion of the histidines opens the opposite side of the binding pocket.     

七种植食性金龟子雌雄成虫的鉴别方法

本研究通过对大黑鳃金龟Holotrichia oblita Faldermann、暗黑鳃金龟H.parallela Motschulsky、铅灰齿爪鳃金龟H.plumbea Hope、铜绿丽金龟Anomala corpulenta Motsch、棕色鳃金龟H.titanis Reitter、拟毛黄鳃金龟H.formosana Moser、小黄鳃金龟Metabolus flavescens Brenske7种常见植食性金龟子的雌雄腹部末端进行显微观察,建立了一种体外无损伤快速准确鉴别常见植食性金龟子雌雄的方法,即轻掰金龟子腹部末端,雌虫可见两片分离的第九腹板退化而成的瓣状褐色骨片,雄虫则无或呈倒"V"字型阳基侧突粘连骨片。该方法对实验所用的鳃金龟、丽金龟2亚科7种金龟子均适用,具有较大的广谱性,且与传统方法相比,操作简便迅速、易于掌握,准确率高。此结果对金龟子田间预测预报以及性信息素的分离研究具有重要意义。6     

The solution NMR structure of Antheraea polyphemus PBP provides new insight into pheromone recognition by pheromone-binding proteins

Pheromone-binding proteins (PBPs) located in the antennae of male moth species play an important role in olfaction. They are carrier proteins, believed to transport volatile hydrophobic pheromone molecules across the aqueous sensillar lymph to the membrane-bound G protein-coupled olfactory receptor proteins. The roles of PBPs in molecular recognition and the mechanisms of pheromone binding and release are poorly understood. Here, we report the NMR structure of a PBP from the giant silk moth Antheraea polyphemus. This is the first structure of a PBP with specific acetate-binding function in vivo. The protein consists of nine alpha-helices: alpha1a (residues 2-5), alpha1b (8-12), alpha1c (16-23), alpha2 (27-34), alpha3a (46-52), alpha3b (54-59), alpha4 (70-79), alpha5 (84-100) and alpha6 (107-125), held together by three disulfide bridges: 19-54, 50-108 and 97-117. A large hydrophobic cavity is located inside the protein, lined with side-chains from all nine helices. The acetate-binding site is located at the narrow end of the cavity formed by the helices alpha3b and alpha4. The pheromone can enter this cavity through an opening between the helix alpha1a, the C-terminal end of the helix alpha6, and the loop between alpha2 and alpha3a. We suggest that Trp37 may play an important role in the initial interaction with the ligand. Our analysis also shows that Asn53 plays the key role in recognition of acetate pheromones specifically, while Phe12, Phe36, Trp37, Phe76, and Phe118 are responsible for non-specific binding, and Leu8 and Ser9 may play a role in ligand chain length recognition.     

小蠹虫信息素的研究与应用现状

小蠹虫是世界性林木害虫,猖獗时常可造成林木成片枯死。利用小蠹虫信息素防治该虫,不仅可以有效降低虫口密度,减轻危害程度,还可以监测小蠹虫的发生为害情况。本文从小蠹虫信息素的分离鉴定、信息素的生物合成、小蠹虫对信息素的行为反应等方面综述小蠹虫信息素的研究与应用现状。     

不同食料对两种金龟甲繁殖力的影响

在室内研究了榆树、樱桃树、核桃树、板栗树、苹果树、柿树、红叶碧桃树、花生叶片对暗黑鳃金龟Holotrichia parallela Motschulsky和铜绿丽金龟Anomqla corpulenta Motschulsky成虫寿命和繁殖力的影响.结果表明,不同食料对两种金龟甲成虫的寿命、产卵期、产卵量有显著影响.取食后使暗黑鳃金龟产生后代由高至低的食料顺序是:榆树叶＞碧桃叶＞板栗叶＞樱桃叶＞花生叶＞核桃叶＞柿叶＞苹果叶,使铜绿丽金龟产生后代由高至低的食料是:核桃叶＞板栗叶＞樱桃叶＞榆叶.在供试的8种食料中,榆树叶片是暗黑鳃金龟成虫的最适宜食料,取食后的寿命、产卵期和产卵量分别为41.5 d、43.0 d和6.2粒/♀;在供试的4种食料中,铜绿丽金龟成虫的最适宜食料是核桃叶片,取食后的寿命、产卵期和产卵量分别为20.9 d、25.0 d和46.8粒/♀.     

The evolution of scarab beetles tracks the sequential rise of angiosperms and mammals

Extant terrestrial biodiversity arguably is driven by the evolutionary success of angiosperm plants, but the evolutionary mechanisms and timescales of angiosperm-dependent radiations remain poorly understood. The Scarabaeoidea is a diverse lineage of predominantly plant- and dung-feeding beetles. Here, we present a phylogenetic analysis of Scarabaeoidea based on four DNA markers for a taxonomically comprehensive set of specimens and link it to recently described fossil evidence. The phylogeny strongly supports multiple origins of coprophagy, phytophagy and anthophagy. The ingroup-based fossil calibration of the tree widely confirmed a Jurassic origin of the Scarabaeoidea crown group. The crown groups of phytophagous lineages began to radiate first (Pleurostict scarabs: 108 Ma; Glaphyridae between 101 Ma), followed by the later diversification of coprophagous lineages (crown-group age Scarabaeinae: 76 Ma; Aphodiinae: 50 Ma). Pollen feeding arose even later, at maximally 62 Ma in the oldest anthophagous lineage. The clear time lag between the origins of herbivores and coprophages suggests an evolutionary path driven by the angiosperms that first favoured the herbivore fauna (mammals and insects) followed by the secondary radiation of the dung feeders. This finding makes it less likely that extant dung beetle lineages initially fed on dinosaur excrements, as often hypothesized.     

A pheromone-binding protein mediates the bombykol-induced activation of a pheromone receptor in vitro

The enormous capacity of the male silkmoth Bombyx mori in recognizing and discriminating bombykol and bombykal is based on distinct sensory neurons in the antennal sensilla hairs. The hydrophobic pheromonal compounds are supposed to be ferried by soluble pheromone-binding proteins (PBPs) through the sensillum lymph toward the receptors in the dendritic membrane. We have generated stable cell lines expressing the candidate pheromone receptors of B. mori, BmOR-1 or BmOR-3, and assessed their responses to hydrophobic pheromone compounds dissolved by means of dimethyl sulfoxide. BmOR-1-expressing cells were activated by bombykol but also responded to bombykal, whereas cells expressing BmOR-3 responded to bombykal only. In experiments employing the B. mori PBP, no organic solvent was necessary to mediate an activation of BmOR-1 by bombykol, indicating that the PBP solubilizes the hydrophobic compound. Furthermore, the employed PBP selectively mediated a response to bombykol but not to bombykal, supporting a ligand specificity of PBPs. This study provides evidence that both distinct pheromone receptors and PBPs play an important role in insect pheromone recognition.     

Seasonal dynamics of scarab beetles (Coleoptera,Lamellicornia) in Voronezh Province

Thirteen seasonal groups of lamellicorn beetles are distinguished in Voronezh Province. Most of the species were found to belong to the spring, late spring-early summer, spring-summer, and summer groups.     

Bombyx mori pheromone-binding protein binding nonpheromone ligands: implications for pheromone recognition

Insect pheromone-binding proteins (PBPs) transport sex pheromones through the aqueous layer surrounding G protein-coupled receptors that initiate signaling events leading to mating. This PBP-receptor system strongly discriminates between ligands with subtle structural differences, but it has proved difficult to distinguish the degree of discrimination of the PBP from that of the G protein-coupled receptor. The three-dimensional structures of the PBP of Bombyx mori, the silkworm moth, both with and without its cognate ligand bombykol ([E,Z]-10,12-hexadecadienol), have been determined by X-ray crystallography and NMR. In this paper, the structures of the same binding protein with bound iodohexadecane and bell pepper odorant were determined at 1.9 and 2.0 A, respectively. These structures illustrate the remarkable plasticity in the ligand binding site of the PBP, but suggest the protein might still act as a filter during pheromone signal processing.     

Olfaction in the gypsy moth, Lymantria dispar: effect of pH, ionic strength, and reductants on pheromone transport by pheromone-binding proteins

The pheromone-binding proteins (PBPs) are 16-kDa abundant proteins in specialized olfactory hairs in insects. The mechanism by which the PBPs remove the pheromone from the inner surface of sensory hairs and deliver it to the sensory cell remains unclear. Existing qualitative models postulate that pheromone is released near the dendrite by a decrease in pH or by a reduced form of the PBP. This study focuses on the two PBPs from the gypsy moth and the enantiomers of the pheromone cis-2-methyl-7,8-epoxyoctadecane. The pH dependence of pheromone binding has revealed three ionizations that are important. The type of ligand influences two of these ionizations. We propose that the (-)-enantiomer of the pheromone interacts with one of the ionizable residues on the protein while the (+)-enantiomer does not. Simultaneous variation of pH and KCl concentration in the physiological range or reduction of disulfide bridges does not change the affinity of PBP for pheromone. We propose a revised model of pheromone transport from the inner surface of the sensory hair to the sensory neuron.     

Discovery of a novel Bacillus thuringiensis Cry8D protein and the unique toxicity of the Cry8D-class proteins against scarab beetles

A novel cry gene, cry8Db, highly toxic to scarab beetles such as the Japanese beetle, Popillia japonica Newman, was cloned from an isolate of Bacillus thuringiensis(Bt), BBT2-5. The cry8Db gene has 3525 bp nucleotides and codes for a protein of 1174 amino acid residues. The protein, Cry8Db, has typical Bt characteristics such as the 8-block, conserved sequences and the three-domain 3 D toxin structure as defined with Cry3Aa. When the amino acid sequence of Cry8Db was compared with that of Cry8Da whose gene was cloned and characterized in our laboratory earlier, substantial sequence diversities were found in their Domain III. The cry8Db gene was expressed in an acrystalliferous B. thuringiensis strain, BT51. BT51 expressing cry8Db formed a spherical crystal like the natural crystal of BBT2-5. The Cry8Db protein was assayed along with the other scarab active Cry8Da and Cry8Ca against the Japanese beetle. While Cry8Da and Cry8Db had toxicity against both adults and larvae of the Japanese beetle, Cry8Ca was toxic to only larvae. Cry8Ca showed no toxicity against the adult beetle up to 30 μg per 1 cm² of leaf discs on which the protein was applied. The activation process of Cry8Db by adult and larval gut juice was compared in vitro with the processes of Cry8Da and Cry8Ca. All three proteins, Cry8Db, Cry8Da and Cry8Ca, produced a toxic core of approximately 70 kDa equally indicating that the activation process does not inactivate the adult activity of Cry8Ca. We concluded that the adult activity of Cry8D proteins is encoded in Domain II. Further tests against other beetle species showed a significant difference between Cry8D’s and Cry8Ca but no difference between Cry8Da and Cry8Db. Comparison of 3D structural models of Cry8Ca, Cry8Da and Cry8Db, which were constructed by using Cry3Bb as the structural template, indicated significant structural differences, especially between Cry8Ca and Cry8D proteins, in three major surface-exposed loops of Domain II that may be involved in determining the adult beetle activity.     

The mode of pheromone evolution: evidence from bark beetles

Sex and aggregation pheromones consist of species-specific blends of chemicals. The way in which different species' blends have evolved has been the subject of some debate. Theoretical predictions suggest that differences between species have arisen not through the accruing of small changes, but through major shifts in chemical composition. Using data on the aggregation pheromones of 34 species of bark beetle from two genera, Dendroctonus and Ips, we investigated how the distributions of the chemical components of their pheromone blends mirror their phylogenetic relationships. We tested whether there were consistent patterns that could be used to help elucidate the mode of pheromone evolution. Although there were obvious differences in pheromone blends between the two genera, the differences between species within each genus followed a less clear phylogenetic pattern. In both genera, closely related species are just as different as more distantly related species. Within Dendroctonus, particularly, most chemical components were distributed randomly across the phylogeny. Indeed, for some chemicals, closely related species may actually be more different than would be expected from a random distribution of chemical components. This argues strongly against the idea of minor shifts in pheromone evolution. Instead, we suggest that, within certain phylogenetic constraints, pheromone evolution in bark beetles is characterized by large saltational shifts, resulting in sibling species being substantially phenotypically (i.e. pheromonally) different from one another, thus agreeing with theoretical predictions.     

Extrusion of the C-terminal helix in navel orangeworm moth pheromone-binding protein (AtraPBP1) controls pheromone binding

The navel orangeworm, Amyelois transitella (Walker), is an agricultural insect pest that can be controlled by disrupting male–female communication with sex pheromones, a technique known as mating disruption. Insect pheromone-binding proteins (PBPs) provide fast transport of hydrophobic pheromones through aqueous sensillar lymph and promote sensitive delivery of pheromones to receptors. Here we present a mutational analysis on a PBP from A. transitella (AtraPBP1) to evaluate how the C-terminal helix in this protein controls pheromone binding as a function of pH. Pheromone binds tightly to AtraPBP1 at neutral pH, but the binding is much weaker at pH below 5. Deletion of the entire C-terminal helix (residues 129–142) causes more than 100-fold increase in pheromone-binding affinity at pH 5 and only a 1.5-fold increase at pH 7. A similar pH-dependent increase in pheromone binding is also seen for the H80A/H95A double mutant that promotes extrusion of the C-terminal helix by disabling salt bridges at each end of the helix. The single mutants (H80A and H95A) also exhibit pheromone binding at pH below 5, but with ∼2-fold weaker affinity. NMR and circular dichroism data demonstrate a large overall structural change in each of these mutants at pH 4.5, indicating an extrusion of the C-terminal helix that profoundly affects the overall structure of the low pH form. Our results confirm that sequestration of the C-terminal helix at low pH as seen in the recent NMR structure may serve to block pheromone binding. We propose that extrusion of these C-terminal residues at neutral pH (or by the mutations in this study) exposes a hydrophobic cleft that promotes high affinity pheromone binding.     

Structure-activity studies with pheromone-binding proteins of the gypsy moth,Lymantria dispar

Pheromone olfaction in the gypsy moth, Lymantria dispar, involves accurate distinction of compounds with similar structure and polarity. The identified sex pheromone is (7R,8S)-2-methyl-7,8-epoxyoctadecane, 1a, and a known antagonist is (7Z)-2-methyloctadec-7-ene, 4a. The first step in pheromone olfaction is binding of odorants by small, soluble pheromone-binding proteins (PBPs), found in the pheromone-sensing hairs. We have studied the molecular determinants recognized by the two PBPs found in the gypsy moth, using three pheromone/PBP binding assays. Results indicate that (i) PBPs bind analogs of the pheromone with some discrimination; (ii) PBPs experience enhancement of binding when presented with 1a or its enantiomer and 4a simultaneously; and (iii) the binding enhancement is also seen at high ligand:PBP ratios. We found no evidence of allostery, so the synergistic binding effects and the concentration effect may only be explained by multimerization of PBPs with each other, which leads to more than one population of binding sites. We suggest that the enhanced ligand binding at high ligand:PBP ratios may serve to sequester excess ligand and thereby attenuate very strong signals.