Metabolism of proctolin, a pentapeptide neurotransmitter in insects

The in vitro metabolism of [tyrosyl-3, 5-3H]proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH) was studied in the following tissues from the American cockroach, Periplaneta americana: proctodeum, midgut, hemolymph, brain, terminal ganglion, and coxal depressor muscles. In all tissues assayed, the Tyr-Leu bond is the primary cleavage site, but scission of the Arg-Tyr bond is also significant. Greater than 90% of the degradative activity is found in the 100,000 X g supernatant from homogenates. In vivo studies with the tobacco hornworm, Manduca sexta, show that topically applied proctolin does not penetrate larval cuticle; proctolin is readily degraded to constituent amino acids (at least to Tyr) upon ingestion.     

Structure of the pentapeptide proctolin, a proposed neurotransmitter in insects.

Proctolin, a myotropic substance with potent activity on the proctodeal (hindgut) muscles of the cockroach, $\text{Periplaneta americana}$ (L.), has been identified by the use of Edman degradation and dansylation techniques as Arg-Tyr-Leu-Pro-Thr. Synthesis of the pentapeptide having this sequence and exhibiting the properties of natural proctolin confirmed the structure. Threshold activity on proctodeal muscle occurs at about 10⁻⁹ M proctolin.     

Role of guanidine group at the N-terminal proctolin chain in cardioexcitatory effects in insects

Six proctolin analogues (I-VI) modified in position 1 of the peptide chain by the following amino acids: homo-Arg, Gac, Gav, Gap, Phe (p-guanidino) and Orn, were synthesized by conventional liquid phase method. The myotropic activity of the obtained peptides was investigated in cardioexcitatory test on two insect species, cockroach, Periplaneta americana L., and yellow mealworm, Tenebrio molitor.     

For uptake of yolk precursors,epithelial cell-oocyte gap junctional communication is required by insects representing six different orders

For uptake of vitellogenin protein into nascent yolk spheres, communication through open gap junction channels between the follicle epithelium and oocyte is required by six different insects representing six different orders. It was recently shown in the hemipteran, Oncopeltus fasciatus, that endocytic uptake of yolk protein resulting in the formation of nascent yolk spheres depended upon an intact epithelium communicating with the oocyte through patent gap junctions. Following treatment with octanol, which down-regulated gap junctions below the level of dye coupling, vitellogenin uptake was terminated. Yet, for another hemipteran, Dysdercus intermedius, it has been shown that yolk spheres can form even when all epithelial cells have been stripped from the oocyte. To determine if the mechanism seen in Oncopeltus is present in other insects, we utilized the same techniques to study nascent yolk sphere production in a dipteran, Drosophila melanogaster, a lepidopteran, Actias luna, a hymenopteran, Xylocopa virginica, a coleopteran, Tenebrio molitor and an orthopteran, Acheta domesticus. In each of these, when gap junctions were down-regulated yolk uptake quickly stopped. That six different insects from six different orders all required a gap junctionally transmitted chemical signal of epithelial cell origin suggests that this mechanism is widespread throughout the insects.     

Oral insecticidal activity of new bacterial isolates against insects in two orders

According to the present research trend and legislative framework of the major world regions fostering the development and use of low-risk biocidal and plant protection products for Integrated Pest Management, the discovery of new entomopathogenic bacterial species and isolates bearing insecticidal traits against novel targets is needed in the near future. In this study, the oral insecticidal activity of bacteria isolated from septicaemic Galleria mellonella larvae was assessed against different insect pests of agricultural, forest and medical-veterinary importance, including Lepidoptera (Lymantria dispar and Malacosoma neustria) and Diptera (Musca domestica and Ceratitis capitata). This led to the identification of new entomopathogenic bacterial isolates belonging to different species including Alcaligenes aquatilis, Alcaligenes faecalis, Enterococcus mundtii, Pseudomonas protegens, Serratia nematodiphila, Serratia marcescens and Stenotrophomonas maltophilia. The majority of these isolates were toxic to gypsy moth L. dispar and, more moderately, to lackey moth M. neustria larvae. Variable degrees of virulence were observed on fly species. While the insecticidal action of some of these species was previously observed, we report for the first time the insecticidal properties of specific strains against a wider target range.     

Characteristics common to a cytokine family spanning five orders of insects

Growth-blocking peptide (GBP) is a member of an insect cytokine family with diverse functions including growth and immunity controls. Members of this cytokine family have been reported in 15 species of Lepidoptera, and we have recently identified GBP-like peptides in Diptera such as Lucilia cuprina and Drosophila melanogaster, indicating that this peptide family is not specific to Lepidoptera. In order to extend our knowledge of this peptide family, we purified the same family peptide from one of the tenebrionids, Zophobas atratus,¹ isolated its cDNA, and sequenced it. The Z. atratus GBP sequence together with reported sequence data of peptides from the same family enabled us to perform BLAST searches against EST and genome databases of several insect species including Coleoptera, Diptera, Hymenoptera, and Hemiptera and identify homologous peptide genes. Here we report conserved structural features in these sequence data. They consist of 19–30 amino acid residues encoded at the C terminus of a 73-152 amino acid precursor and contain the motif C-x(2)-G-x(4,6)-G-x(1,2)-C-[KR], which shares a certain similarity with the motif in the mammalian EGF peptide family. These data indicate that these small cytokines belonging to one family are present in at least five insect orders.     

北京地区六种蜜蜂病毒病的流行病学研究

【目的】对蜜蜂的6种病毒:以色列急性麻痹病毒(Israeli acute paralysis virus,IAPV)、残翅病毒(Deformed wing virus,DWV)、囊状幼虫病病毒(Sacbrood virus,SBV)、急性蜜蜂麻痹病毒(Acute bee paralysis virus,ABPV)、黑蜂王台病毒(Black queen cell virus,BQCV)、慢性麻痹病毒(Chronic bee paralysis virus,CBPV)在北京地区的流行情况进行调查,以期为该地区蜜蜂病毒病的防控提供一定的理论依据。【方法】应用多重RT-PCR法确定上述6种病毒在该地区的感染情况,并通过序列分析确定特异性。【结果】在所有检测样本中均未检测到急性麻痹病病毒和慢性麻痹病病毒,感染率最高的是以色列急性麻痹病毒,其次是残翅病毒。检测的样本普遍存在混合感染。【结论】以色列急性麻痹病毒、残翅病毒、囊状幼虫病病毒、黑蜂王台病毒4种病毒可能在北京地区广泛分布。     

Trends in genome dynamics among major orders of insects revealed through variations in protein families

Background

Insects belong to a class that accounts for the majority of animals on earth. With over one million identified species, insects display a huge diversity and occupy extreme environments. At present, there are dozens of fully sequenced insect genomes that cover a range of habitats, social behavior and morphologies. In view of such diverse collection of genomes, revealing evolutionary trends and charting functional relationships of proteins remain challenging.

Results

We analyzed the relatedness of 17 complete proteomes representative of proteomes from insects including louse, bee, beetle, ants, flies and mosquitoes, as well as an out-group from the crustaceans. The analyzed proteomes mostly represented the orders of Hymenoptera and Diptera. The 287,405 protein sequences from the 18 proteomes were automatically clustered into 20,933 families, including 799 singletons. A comprehensive analysis based on statistical considerations identified the families that were significantly expanded or reduced in any of the studied organisms. Among all the tested species, ants are characterized by an exceptionally high rate of family gain and loss. By assigning annotations to hundreds of species-specific families, the functional diversity among species and between the major clades (Diptera and Hymenoptera) is revealed. We found that many species-specific families are associated with receptor signaling, stress-related functions and proteases. The highest variability among insects associates with the function of transposition and nucleic acids processes (collectively coined TNAP). Specifically, the wasp and ants have an order of magnitude more TNAP families and proteins relative to species that belong to Diptera (mosquitoes and flies).

Conclusions

An unsupervised clustering methodology combined with a comparative functional analysis unveiled proteomic signatures in the major clades of winged insects. We propose that the expansion of TNAP families in Hymenoptera potentially contributes to the accelerated genome dynamics that characterize the wasp and ants.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1771-2) contains supplementary material, which is available to authorized users.     

Transepithelial transport of salicylate by the Malpighian tubules of insects from different orders

The organic anion salicylate is a plant secondary metabolite that protects plants against phytophagous insects. In this study, a combination of salicylate-selective microelectrodes and a radioisotope tracer technique was used to study the transepithelial transport of salicylate by the Malpighian tubules of 10 species of insects from five orders. Our results show that salicylate is transported into the lumen of the Malpighian tubules in all the species evaluated, except Rhodnius prolixus. The transepithelial transport of salicylate by the Malpighian tubules of Drosophila simulans, Drosophila erecta, Drosophila sechellia, and Acheta domesticus was saturable, Na⁺-dependent and inhibited by α-cyano-4-hydroxycinnamic acid. This transport system resembles that previously found in tubules of Drosophila melanogaster. In contrast, transepithelial transport of salicylate by Malpighian tubules of Tenebrio molitor, Plagiodera versicolora, Aedes aegypti, and Trichoplusia ni was unaffected by Na⁺-free bathing saline. The presence of both salicylate and salicylate metabolites in the secreted fluid samples from the Malpighian tubules of A. domesticus, R. prolixus, T. molitor, and T. ni indicates that insect Malpighian tubules may both transport and metabolize salicylate. The highest capacities to rid the hemolymph of salicylate were found in T. molitor, P. versicolora and Drosphila spp. Our results suggest that transport of salicylate by the Malpighian tubules might contribute to elimination of this organic anion from the hemolymph, particularly in some species that encounter high levels of organic anion in the diet.     

落叶松冠部6种病虫生态效应的研究

落叶松落叶病、枯梢病、褐锈病、兴安落叶松鞘蛾、落叶松球蚜、大蚜同为落叶松冠层的主要病虫害,但各具不同的生态位．不同害虫（ 包括虫态） 、病害对落叶松冠层的作用时序均具交错出现、相互回避的现象．对生态环境亦各有不同选择,鞘蛾和球蚜大都喜于平坦、阳坡的林分,林分郁闭度０ ．８ ～０ ．５ 为宜,尤以鞘蛾更喜于林缘和林分的天窗．通过对病虫害的综合作用研究,从落叶松生长期６ 种病虫作用生命表中得知,自５ 月下旬至７ 月上旬,落叶松冠层中以害虫危害为主,自７ 月下旬病害加入,使林木受害逐渐加重．仅有３ 种害虫危害时,生命表中Ｋｘ 值为０ ．０１６ ～０ ．０１９７ ,病害加入后Ｋｘ 值增至０ ．１２４ ,９ 月７ 日Ｋｘ 值达０ ．２６ ．３ 种病害的大量失叶时间为８ 月,可连续影响３ 年生长,影响最大者为第２ 年,鞘蛾在５ 月造成大量失叶．     

Further studies on proctolin analogues modified in position 2 of the peptide chain and their influence on heart-beat frequency of insects

Seven proctolin analogues (I-VII) modified in position 2 of the peptide chain by Phe (p-guanidino) (I), Phe (p-OEt) (II), Tyr (3'-NH2) (III), Tyr (3'-NO2) (IV), Afb (p-OH) (V) (Afb = 3-amino-4-phenyl-L-butyric acid), Afb (p-NH2) (VI), Afb (p-NO2) (VII), and the tetrapeptide Tyr (3'-NH2)-Leu-Pro-Thr (VIII) were synthesized by the classic liquid-phase method. The biological effects of the peptides were investigated in cardioexcitatory tests on two insect species, the cockroach Periplaneta americana L., and the yellow mealworm, Tenebrio molitor L. Within physiological concentrations (10(-9)-10(-7) M) peptides II, III, and IV stimulated the heart action of P. americana like proctolin itself. Under identical conditions, in the case of T. molitor, only peptide III showed cardiostimulatory properties, whereas other compounds (including II and IV) were inactive at concentrations up to 10(-7) M. Results reported here reflect, with reference to the analogues I-VII, selective recognition of receptors on myocardium of both insect species. The tetrapeptide VIII revealed a weak deacceleratory effect on P. americana and T. molitor heart action.     

Evolution of the mitochondrial cytochrome oxidase II gene among 10 orders of insects.

We examine the complete nucleotide sequences of the mitochondrial cytochrome oxidase II gene of 13 species of insects, representing 10 orders. The genes range from 673 to 690 bp in length, encoding 226 to 229 amino acids. Several insertion or deletion events, each involving one or two codons, can be observed. The 3' end of the gene is extremely variable in both length and sequence, making alignment of the ends unreliable. Using the first 639 nucleotide positions, for which unambiguous alignments could be obtained, we examine the neighbor-joining trees based on nucleotide divergences and based on conserved subsets of that data, including transversion and amino acid and second codon position divergences. Each of these subsets produces different trees, none of which can be easily reconciled with trees constructed using morphology and the fossil record. Bootstrap analysis using second codon positions strongly supports affinities between the order Blatteria (cockroaches) and the order Isoptera (termites) and between a wasp and the published honeybee sequence (Order Hymenoptera). The divergence of insect orders is very ancient and may have occurred too rapidly for easy resolution using mitochondrial protein sequences. Unambiguous resolution of insect orders will probably require analysis of many additional taxa, using the COII gene and other conserved sequences.     

Occurrence and dominance of six Pacific Northwest conifer species

Questions: Can probability of occurrence and dominance be accurately estimated for six important conifer species with varying range sizes? Does range size impact the accuracy of species probability of occurrence models? Is species predicted probability of occurrence significantly related to observed dominance? Location: Pacific Northwest region, North America (60°–40°N, 140°–110°W). Methods: This study develops near range‐wide predictive distribution maps for six important conifer species (Pseudotsuga menziesii, Tsuga heterophylla, Pinus contorta, Thuja plicata, Larix occidentalis, and Picea glauca) using forest inventory data collected across the United States and Canada. Species model accuracies are compared with range size using a rank scoring system. A suite of climate and topographic predictor variables are used to investigate environmental constraints that limit species range and quantify relationships between species predicted probability of occurrence and dominance at both plot and landscape scales. Results: Evaluation statistics revealed significant and accurate probability of occurrence models were developed for all six species. Based on ranked evaluation statistics, Tsuga heterophylla had highest overall model accuracy (statistic rank score=5) and Pinus contorta the lowest (statistic rank score=17). Across species, ranked evaluation statistics also revealed a pattern of decreasing model accuracy with increasing range size. At plot level, correlations between dominance and probability of occurrence were weakly positive for all species with only half of the species having statistically significant correlations. Pseudotsuga menziesii had the highest correlation (r=0.36, P<0.001) and Thuja plicata lowest (r=0.038, P=0.799). At the 50‐km scale, correlations between dominance and probability of occurrence improved for all species except Pinus contorta. Pseudotsuga menziesii displayed the highest correlation (r=0.68, P<0.001) and Thuja plicata the lowest (r=0.07, P>0.709). Conclusions: Species probability of occurrence model accuracy decreased with increasing range size. The strength and significance of correlations between probability of occurrence and dominance varied considerably by species and across spatial scales. Apart from Pseudotsuga menziesii and L. occidentalis, the results suggest that probability of occurrence is not a consistently reliable surrogate for species dominance in Pacific Northwest forests. We demonstrate how the degree of correlation between species occurrence and dominance can be used as an indicator of how well predictions of occurrence characterize the optimal niche of a species.     

6种颜色粘虫板对春季菜地昆虫的诱集效应

为筛选对春季蔬菜害虫具有较好诱集效果的粘虫板,促进蔬菜害虫绿色防控技术的研究与推广,采用红色、黄色、绿色、蓝色、白色和黑色6种颜色的市售粘虫板对菜地昆虫进行诱集试验.结果显示,粘虫板诱集的害虫以尖眼蕈蚊Bradysia minpleuroti、小菜蛾Plutella xylostella、端大蓟马Megalurothrips distalis和黄蓟马Thrips flavus为优势种;黄曲条跳甲Phyllotreta striolata、南美斑潜蝇Liriomyza huidobrensis、灰地种蝇Delia platura、棉蚜Aphis gossypii、小绿叶蝉Empoasca flavescens、菜粉蝶Pieris rapae为常见种.试验中蓝色粘虫板诱集的灰地种蝇的数量显著高于其它处理组(P<0.05);黄色粘虫板诱集的南美斑潜蝇、棉蚜、小绿叶蝉的数量显著高于其它处理组(P<0.05);蓝色和白色粘虫板诱集的端大蓟马、黄蓟马的数量显著高于其它处理组(P<0.05);蓝色粘虫板诱集到的尖眼蕈蚊的数量显著低于其它处理组(P<0.05).各种颜色粘虫板诱集昆虫的益害比较低,诱集益虫总数仅占诱集昆虫总数的1.64％,表明该时段使用粘虫板防治菜地害虫,对益虫伤害较小,对保护利用天敌昆虫具有重要意义.本研究结果为科学使用粘虫板防治菜地害虫提供理论依据.