Mode of action of insect growth regulators in lepidopteran tissue culture

Insect growth regulators (IGRs) have been proposed as agents for the control of insect pests. These compounds disrupt the normal development of insects by mimicking juvenile hormone and the molting hormone, 20-hydroxyecdsyone, or by interfering with chitin synthesis. The effectiveness and selectivity of IGRs provide new tools for integrated pest management. The simultaneous advances in the chemistry of IGRs and the ability to study insect tissues in culture, have led to research on the mode of action of IGRs in vitro. Plodia interpunctella and Spodoptera frugiperda have been used to examine the effects of IGRs on wing imaginal discs in organ culture, as well as in hormonally responsive cell lines established from wing imaginal discs of these species. Our research has focused on the action of ecdysteroid mimics, chitin synthesis inhibitors and juvenile hormone mimics. The effects of the IGRs on chitin synthesis, uptake of amino-sugars, and cellular proliferation were studied in tissue culture. The results demonstrate the effectiveness of using organ cultures and hormonally responsive cell lines for investigating IGRs at the cellular and tissue level. © 1998 Society of Chemical Industry     

Met基因在黏虫生殖中的功能分析

保幼激素(juvenile hormone, JH)是由咽侧体分泌的倍半萜类化合物,可以调控昆虫的很多生理过程,如发育、变态、生殖等。作为bHLH-PAS(helix-loop-helix-Per-ARNT-Sim)转录因子家族成员之一的methoprene-tolerant (Met)是JH的受体,在JH的信号传导过程中有非常重要的作用。本研究通过实时荧光定量PCR结合RNAi技术测定了沉默Met基因后黏虫Mythimna separata的Vg基因表达、卵巢发育和生殖行为,旨在探究Met基因在黏虫生殖过程中的功能。结果表明当Met基因沉默后,与卵巢发育密切相关的卵黄原蛋白(vitellogenin, Vg)基因表达量下调了50%,从而显著抑制了卵巢发育,并导致产卵显著延迟、产卵历期显著缩短,产卵量显著下降。结果表明Met基因是黏虫生殖发育过程中的关键受体基因,它通过调节后续Vg的表达和沉积,来达到控制卵巢发育,从而调控生殖作用。     

七星瓢虫保幼激素环氧水解酶基因克隆及表达分析

保幼激素(juvenile hormone, JH)可以调控昆虫滞育,保幼激素环氧水解酶(juvenile hormone epoxide hydrolase, JHEH)是调节保幼激素代谢的关键酶之一。为探索JHEH在七星瓢虫Coccinella septempunctata L.滞育中的调控作用,利用RT-PCR和RACE技术克隆获得七星瓢虫JHEH全长基因,命名为Csjheh(GenBank登录号:MH932586),该基因cDNA全长2 077 bp,开放阅读框(ORF)1 380 bp,编码459个氨基酸,预测蛋白质分子量为51.39 kD,理论等电点(pI)为8.79。疏水性分析结果显示该基因具有典型环氧水解酶的N末端疏水结构。氨基酸序列比对结果表明,Csjheh与中欧山松大小蠹、赤拟谷盗、丽蝇蛹集金小蜂、内华达古白蚁保幼激素环氧水解酶同源性达到64.24%。利用实时荧光定量PCR技术研究其时空表达模式,结果表明Csjheh基因在七星瓢虫成虫初羽化阶段表达量较高,滞育诱导条件下表达量呈先下降后上升的趋势,滞育60 d时与初羽化阶段接近。本研究结果对揭示JHEH参与JH的调控作用,进而调控昆虫滞育提供了理论参考。     

Effects of juvenile hormone analog formulations on development and reproduction in the bed bug Cimex lectularius (Hemiptera: Cimicidae)

BACKGROUND: Bed bugs (Cimex lectularius L.) have become a common insect pest in urban areas and are often difficult to manage. Eradication is made more problematic by widespread insecticide resistance, raising interest in alternative control products. Juvenile hormone analogs (JHAs) such as methoprene and hydroprene are relatively harmless to non‐arthropods and have proved to be effective against other urban insect pests. Two JHA products (Gentrol^® and Precor^®, Central Life Sciences, Schaumburg, IL) were tested for efficacy against various bed bug stages as direct spray and as dry residue using three bed bug strains. RESULTS: At 1× and 2× the label rate, Precor^® [active ingredient (S)‐methoprene] had no significant effect on the development or fecundity of bed bugs. At 2× the label rate, confinement to residues of Gentrol^® [active ingredient (S)‐hydroprene] had no significant effect, but residues at 3× and 10× the label rate caused a reduction in fecundity and impaired development. Field strains were more susceptible to the reproductive effects of (S)‐hydroprene than a long‐maintained laboratory strain. CONCLUSIONS: While JHAs are attractive alternatives for pest management because of their inherent safety and distinct mode of action, these JHA formulations would have little impact on bed bug populations without relabeling to allow for higher application rates. Copyright © 2012 Society of Chemical Industry     

喜树碱对小菜蛾体内保幼激素及蜕皮激素滴度的影响

为明确喜树碱对小菜蛾Plutella xylostella生长发育的抑制作用及其机制,设置0.5、1.0、2.0mg/m L剂量处理其3龄幼虫,采用浸叶饲喂法和高效液相色谱法测定了喜树碱对小菜蛾体内蜕皮激素和保幼激素滴度的影响。结果显示,喜树碱各剂量处理均显著抑制了小菜蛾幼虫的生长发育,抑制率最高达到28.42%;各处理小菜蛾化蛹时间均延迟,异常蛹增多,羽化率降低;其中2.0 mg/m L处理后4 d其化蛹率为6.67%,对照组化蛹率为86.60%。0.5、1.0 mg/m L处理下,小菜蛾体内蜕皮激素滴度显著低于对照组,仅为对照组的0.06倍;而保幼激素滴度增加,分别可达到28.74mg/m L和36.29 mg/m L,是对照组的9倍左右。表明喜树碱可影响小菜蛾体内蜕皮激素和保幼激素的平衡,延迟和影响了小菜蛾的正常发育进程,可实现对小菜蛾种群的控制作用。     

Ovicidal activity of juvenile hormone mimics in the bean bug,Riptortus pedestris

Insect juvenile hormone (JH) mimics (JHMs) are known to have ovicidal effects if applied to adult females or eggs. Here, we examined the effects of exogenous JHMs on embryonic development of the bean bug, Riptortus pedestris. The expression profiles of JH early response genes and JH biosynthetic enzymes indicated that JH titer was low for the first 3 days of the egg stage and increased thereafter. Application of JH III skipped bisepoxide (JHSB₃) or JHM on Day 0 eggs when JH titer was low caused reduced hatchability, and the embryos mainly arrested in mid- or late embryonic stage. Application of JHMs on Day 5 eggs also resulted in an arrest, but this was less effective compared with Day 0 treatment. Interestingly, ovicidal activity of synthetic JHMs was much lower than that of JHSB₃. This study will contribute to developing novel insecticides that are selective among insect species.     

荻草谷网蚜ABCG1基因的克隆及表达模式分析

荻草谷网蚜Sitobion miscanthi是严重威胁我国小麦生产安全的迁飞性害虫。蜕皮激素是参与蚜虫翅型分化调控的内激素, 在有翅成蚜体内保持高滴度, 且诱导后代产生更高比例的无翅蚜, 其进出靶细胞需要经过细胞膜上特定蛋白的转运。ATP结合盒转运蛋白家族G亚家族(ATP-binding cassette transporter G, ABCG)中的 ABCG1是通过跨膜转运昆虫类固醇、对蜕皮激素信号进行负调控的功能蛋白之一, 在蚜虫中尚未见报道。本文克隆了荻草谷网蚜ABCG1(SmisABCG1)基因, 并进行了序列比对、系统进化分析以及不同组织部位和发育时期表达模式分析。结果显示, SmisABCG1基因的开放阅读框全长为1 851 bp, 编码616个氨基酸, 含7个跨膜结构域, 符合ABCG蛋白家族典型结构特性, 基因登录ID:OP626323。昆虫间ABCG1较保守, 该蛋白系统进化关系与各自物种间亲缘关系的远近保持一致。其中, SmisABCG1与来自豌豆蚜、禾谷缢管蚜、棉蚜、花生蚜和雪松长足大蚜等的ABCG1氨基酸序列高度一致(>87%), 以上蚜虫聚为一支。与SmisABCG1亲缘关系最近的是豌豆蚜的ABCG1, 其次是半翅目的褐飞虱、白背飞虱和灰飞虱, 与膜翅目的新疆菜叶蜂、阿里山潜蝇茧蜂以及鞘翅目的赤拟谷盗、蜂箱小甲虫亲缘关系较远。该基因在伪胚胎和成蚜阶段高表达。包含伪胚胎的有翅、无翅成蚜整蚜SmisABCG1的转录水平无显著差异, 但其在来自有翅成蚜的伪胚胎中的转录水平高于无翅成蚜伪胚胎, 证实无翅成蚜自身的转录水平较高, 而有翅成蚜较低。进一步分析显示这一差异主要是无翅蚜胸部显著高表达所导致。基于该蛋白对蜕皮激素负调控, 与有翅成蚜转录水平低, 但蜕皮激素水平更高相符合。     

粘虫脂动激素基因MsepAKH1的克隆与成虫期表达模式分析

为明确脂动激素基因AKH在粘虫Mythimna separata(Walker)能源代谢过程中的作用,采用RT-PCR和RACE技术克隆得到粘虫脂动激素基因MsepAKH1的cDNA全长,并通过实时荧光定量PCR技术测定该基因在成虫期的组织与发育阶段表达模式。结果表明,粘虫脂动激素基因MsepAKH1的cDNA序列全长为449 bp,GenBank登录号为KP979739.1,开放阅读框为207 bp,编码68个氨基酸,具有昆虫脂动激素基因家族典型的结构特征;预测该基因编码的MsepAKH1蛋白分子量为7.61 kD,等电点为8.46,MsepAKH1的氨基酸序列与烟草天蛾Manduca sexta、二化螟Chilo suppressalis、小菜蛾Plutella xylostella、棉铃虫Helicoverpa armigera、家蚕Bombyx mori的AKH氨基酸序列同源性较高。MsepAKH1基因在粘虫初羽化雌蛾不同组织间的表达量差异显著,主要在头部和飞行肌内表达,分别约为同日龄雌蛾脂肪体内表达量的15.4倍与8.1倍,在脂肪体、卵巢与中肠内的表达量显著降低。对不同日龄雌蛾头部和飞行肌内的表达量检测发现,在7日龄雌蛾头部和3日龄雌蛾飞行肌内的表达量分别显著高于其它日龄雌蛾相同组织中的表达量,分别约为初羽化雌蛾相同组织表达量的2.4倍与1.6倍。表明MsepAKH1基因的表达因粘虫雌蛾组织与日龄间的不同而呈现动态变化。     

Mode of reproduction of Barbarea vulgaris in two different habitats in Tohoku, Japan

This study was conducted to determine the reproductive characteristics of Barbarea vulgaris under different disturbance regimes (mowing and tilling) in two different habitats: a levee and a wheat field. On the levee, 77 of the 114 individuals that had had their floral stalks removed by the first mowing produced new rosettes at the basal part of the stem during the same growing season. The plants that were mowed four times per year had a significantly greater survival rate than the plants that were mowed twice per year. The levee population that was mowed without tillage was largely maintained by vegetative reproduction. These results suggest that mowing the levees promotes the vegetative reproduction of B. vulgaris and helps it to compete with tall-growing plants, thus facilitating its survival as a perennial. In spite of the high sprouting ability of the plant's root fragments, most of the root fragments did not regenerate when buried or when exposed to high soil moisture conditions in tilled wheat fields. The population of B. vulgaris in tilled wheat fields was maintained almost entirely by sexual reproduction. Barbarea vulgaris can survive under two different management regimes by altering its mode of reproduction.     

Juvenile hormonal activity of mono- and polyenehomobenzenes in Drosophila virilis, Spodoptera frugiperda and Araschnia levana

A series of mono- and polyenehomobenzenes was synthesised by a highly regioselective palladium-catalysed allylic alkylation of substituted and unsubstituted benzylic Grignard reagents employing catalytic amounts of catalyst and tested for juvenile hormone activity on the fruit fly Drosophila virilis Sturtevant (Diptera: Drosophilidae), on an important agricultural pest species, the fall armyworm Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae), and on the map butterfly Araschnia levana L. (Lepidoptera: Nymphalidae). In D. virilis only polyenehomobenzenes with a geranyl chain and a methyl, methoxy or isopropyl group at the para position of the aromatic ring displayed significant juvenile hormonal activity at low doses. A monoenehomobenzene and polyenehomobenzenes with longer allylic chains or without a substituted aromatic ring were not active. In S. frugiperda and in A. levana, a mono-, a di- and a tetraene displayed juvenile hormonal activity. In the lepidopteran species, a trend for the necessity of a substitution at position 4 of the phenyl group for high juvenile hormonal activity was also found.     

Mode of action of the delayed toxicity of O,O,S-trimethyl phosphorothioate in the rat

As preliminary probes to determine the mode of delayed toxic action of O,O,S-trimethyl phosphorothioate (I) in the rat, the effect of I on rat tissue and organs, and on blood, urine, and pharmacokinetic parameters was investigated. Following oral administration, 30 to 200 mg/kg I caused liver necrosis as a major pathological effect. Morphological changes were also observed in the heart, adrenal, tissues of the small intestine, and kidney. Most animals treated with I developed bronchopneumonia after 3 days. Blood samples taken from rats poisoned with 60 mg/kg I showed severe hemoconcentration; however, serum Na⁺, Cl^?, albumin, and total carbonate/bicarbonate varied only slightly. Na⁺ and Cl^? concentrations in the urine showed a steady decline with time following poisoning but K⁺ levels remained relatively constant. Pharmacokinetic studies showed that ¹⁴C levels in the blood following intraperitoneal or intravenous administration of 60 mg/kg [CH₃O¹⁴C]I were not affected when the animals were cotreated with 5% of the antagonist O,O,O-trimethyl phosphorothioate. However, lower levels of ¹⁴C were found in antagonized animals following oral administration.