Genetic Transformation of Crops for Insect Resistance: Potential and Limitations

Transgenic resistance to insects has been demonstrated in plants expressing insecticidal genes such as δ -endotoxins from Bacillus thuringiensis (Bt), protease inhibitors, enzymes, secondary plant metabolites, and plant lectins. While transgenic plants with introduced Bt genes have been deployed in several crops on a global scale, the alternative genes have received considerably less attention. The protease inhibitor and lectin genes largely affect insect growth and development and, in most instances, do not result in insect mortality. The effective concentrations of these proteins are much greater than the Bt toxin proteins. Therefore, the potential of some of the alternative genes can only be realized by deploying them in combination with conventional host plant resistance and Bt genes. Genes conferring resistance to insects can also be deployed as multilines or synthetic varieties. Initial indications from deployment of transgenics with insect resistance in diverse cropping systems in USA, Canada, Argentina, China, India, Australia, and South Africa suggest that single transgene products in standard cultivar backgrounds are not a recipe for sustainable pest management. Instead, a much more complex approach may be needed, one which may involve deployment of a combination of different transgenes in different backgrounds. Under diverse climatic conditions and cropping systems of tropics, the success in the utilization of transgenics for pest management may involve decentralized national breeding programs and several small-scale seed companies. While several transgenic crops with insecticidal genes have been introduced in the temperate regions, very little has been done to use this technology for improving crop productivity in the harsh environments of the tropics, where the need for increasing food production is most urgent. There is a need to develop appropriate strategies for deployment of transgenics for pest management, keeping in view the pest spectrum involved, and the effects on nontarget organisms in the ecosystem.     

Effective bacterial insecticidal proteins against coleopteran pests: A review

Coleoptera, the order of insects commonly referred to as beetles, are able to survive in various environments, and thus, comprise the largest order in the animal kingdom. Coleopterans mainly include coprophagous and phytophagous lineages, and many species of the latter lineage are serious pests. In addition to traditional chemical methods, biocontrol measures using various bacterial insecticidal proteins have also gradually been developed to control these insect pests. In this review, we summarized the possible coleopteran‐pest‐specific bacteria and insecticidal proteins that have been reported in the literature thus far and have provided a comprehensive overview and long‐term guidance for the control of coleopteran pests in the future.     

Protein proteinase inhibitor genes in combat against insects, pests, and pathogens: natural and engineered phytoprotection

The continual need to increase food production necessitates the development and application of novel biotechnologies to enable the provision of improved crop varieties in a timely and cost-effective way. A milestone in this field was the introduction of Bacillus thuringiensis (Bt) entomotoxic proteins into plants. Despite the success of this technology, there is need for development of alternative strategies of phytoprotection. Biotechnology offers sustainable solutions to the problem of pests, pathogens, and plant parasitic nematodes in the form of other insecticidal protein genes. A variety of genes, besides (Bt) toxins that are now available for genetic engineering for pest resistance are genes for vegetative insecticidal proteins, proteinase inhibitors, alpha-amylase inhibitors, and plant lectins. This review presents a comprehensive summary of research efforts that focus on the potential use and advantages of using proteinase inhibitor genes to engineer insect- and pest-resistance. Crop protection by means of PI genes is an important component of Integrated Pest Management programmes.     

转Bt基因抗虫作物对鳞翅目非靶标昆虫生态影响的研究进展

任何转基因作物在进入商业化应用之前都必须经过严格的环境风险评价。评价转基因作物特别是抗虫作物对农田重要非靶标节肢动物的生态影响是其中一项重要内容。当前,全球种植的转基因抗虫作物大多表达对鳞翅目害虫具有活性的Cry1或Cry2类杀虫蛋白。由于非靶标鳞翅目昆虫如斑蝶、家蚕等与靶标害虫具有较近的亲缘关系,其幼虫可能同样对这类杀虫蛋白敏感。因此,这类转基因抗虫作物对非靶标鳞翅目害虫的潜在影响引起了研究者的广泛关注。在总结国内外相关研究数据的基础上,系统分析了转基因抗虫作物对非靶标蝶类和蚕类昆虫的潜在影响,获得以下结论：虽然蚕类和蝶类昆虫对Cry1或Cry2类杀虫蛋白敏感,但在自然条件下这类非靶标昆虫暴露于Cry杀虫蛋白的水平很低,抗鳞翅目害虫转基因作物的种植不可能显著影响田间蝶类昆虫的种群密度,也不会给我国的蚕丝产业带来负面影响。     

Plant‐insect interactions: what can we learn from plant lectins?

Many plant lectins have high anti‐insect potential. Although the effects of most lectins are only moderately influencing development or population growth of the insect, some lectins have strong insecticidal properties. In addition, some studies report a deterrent activity towards feeding and oviposition behavior. Transmission of plant lectins to the next trophic level has been investigated for several tritrophic interactions. Effects of lectins with different sugar specificities can vary substantially with the insect species under investigation and with the experimental setup. Lectin binding in the insect is an essential step in exerting a toxic effect. Attempts have been made to study the interactions of lectins in several insect tissues and to identify lectin‐binding receptors. Ingested lectins generally bind to parts of the insect gut. Furthermore, some lectins such as the Galanthus nivalus agglutinin (GNA) cross the gut epithelium into the hemolymph and other tissues. Recently, several candidate lectin‐binding receptors have been isolated from midgut extracts. To date little is known about the exact mechanism for insecticidal activity of plant lectins. However, insect glycobiology is an emerging research field and the recent technological advances in the analysis of lectin carbohydrate specificities and insect glycobiology will certainly lead to new insights in the interactions between plant lectins and insects, and to a better understanding of the molecular mechanisms involved. © 2010 Wiley Periodicals, Inc.     

蘑菇子实体内杀虫蛋白质的研究

许多蘑菇都对昆虫表现出毒性。为了证实与杀虫毒性有关的化合物,对14种蘑菇的毒性在水溶性、热敏性和可透析性等方面进行了研究。研究数据表明,蛋白质对大多数蘑菇子实体的杀虫活性起着重要作用,也许是一种可以用于植物抵抗害虫的基因源。在数种蛋白质中,凝集素和溶血素因不受蛋白酶的影响而成为良好的杀虫剂候选材料。     

植食性昆虫适应植物防御反应的研究进展

在植物与植食性昆虫协同进化过程中,植物在不断完善其防御反应,同时植食性昆虫也在选择压下不断适应植物防御反应。植食性昆虫适应植物防御反应存在多样性。昆虫能够利用其唾液中的效应因子抑制或弱化植物防御反应,激活其肠道中的某些特异性蛋白阻断植物防御性次生代谢物的产生或者将其直接降解,以及通过其携带微生物间接抑制植物防御反应。此外,昆虫还能够通过产卵、虫害诱导植物挥发物、识别植物防御物质等方式适应植物的防御反应。本文综述了植食性昆虫如何利用各种效应因子适应寄主植物防御反应的研究进展。     

Proteins as active compounds involved in insecticidal activity of mushroom fruitbodies

Many mushrooms are toxic to insects. To identify the chemicals involved in insecticidal activity, the toxicity of 14 species has been studied for water solubility, thermolability, and dialysis. The data strongly suggest that proteins are responsible for most of the insecticidal activity of mushroom fruitbodies and may be a source of genes available for plant protection against insects. Among proteins, lectins and hemolysins were good insecticide candidates because the toxicities were not affected by protease.     

植食性昆虫学习行为与害虫治理的关系

植食性昆虫的学习行为一般具有习惯性反应、厌恶性学习、联系性学习、敏感性反应、嗜好性诱导几种类型,它们对害虫防治方法的效果具有重要影响。害虫通过嗜好性诱导对栖境中大面积单作农作物造成更大的危害,通过联系性学习可对诱虫植物的效果产生积极或消极的影响。害虫对驱避剂或杀虫剂等产生习惯性反应可降低其防治效果。害虫对寄主植物驱避抗性产生习惯性学习就会加重对作物的为害,产生厌恶性学习则有利于对作物的保护。利用害虫的联系性学习行为,释放前让不育雄虫学习自然交配场所的环境刺激,可增强通过释放不育雄虫控制害虫的防治效果。了解植食性昆虫学习行为对害虫治理的影响有助于研究和发展有效的栖境调控、行为调控等策略和方法。     

植物与植食性昆虫化学互作研究进展

植物与植食性昆虫之间存在着复杂的化学相互作用。一方面,当遭受植食性昆虫为害时,植物能识别植食性昆虫相关分子模式,触发早期信号事件和激素信号转导途径,并由此引起转录组与代谢组重组、直接和间接防御化合物含量升高,最后提高对植食性昆虫的抗性。另一方面,植食性昆虫也能识别植物的防御反应,并能通过分泌效应子、选贮、解毒以及降低敏感性等反防御措施抑制或适应植物的化学防御。深入剖析植物与植食性昆虫的化学互作,不仅可在理论上丰富对昆虫与植物互作关系的理解,而且可在实践上为作物害虫防控新技术的开发提供重要的理论与技术指导。     

Pest management through Bacillus thuringiensis (Bt) in a tea-silkworm ecosystem: status and potential prospects

Bacillus thuringiensis (Bt) is a soil bacterium that forms spores containing crystals comprising one or more Cry or Cyt proteins having potential and specific insecticidal activity. Different strains of Bt produce different types of toxins, affecting a narrow taxonomic group of insects. Therefore, it is used in non-chemical pest management, including inherent pest resistance through GM crops. The specificity of action of Bt toxins reduces the concern of adverse effects on non-target species, a concern which remains with chemical insecticides as well. To make use of Bt more sustainable, new strains expressing novel toxins are actively being sought globally. Since Bt is successfully used against many pests including the lepidopteran pests in different crop groups, the insecticidal activity against Samia cynthia (Drury) (Eri silkworm) and Antheraea assamensis Helfer (Muga silkworm) becomes a concern in the state of Assam in India which is a predominantly tea- and silk-producing zone. Though Bt can be used as an effective non-chemical approach for pest management for tea pests in the same geographical region, yet, it may potentially affect the silk industry which depends on silkworm. There is a need to identify the potentially lethal impact (through evaluating their mortality potential) of local Bt strains on key silkworm species in North Eastern India. This will allow the use of existing Bt for which the silkworms have natural resistance. Through this review, the authors aim to highlight recent progress in the use of Bt and its insecticidal toxins in tea pest control and the potential sensitivity for tea- and silk-producing zone of Assam in India.

     

Non-target organism effects tests on Vip3A and their application to the ecological risk assessment for cultivation of MIR162 maize

Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) provide economic, environmental and health benefits by maintaining or increasing crop yields with fewer applications of insecticide. To sustain these benefits, it is important to delay the evolution of insect resistance to the proteins, and to ensure that the proteins do not harm non-target organisms, particularly those that may control secondary pests that would otherwise flourish because of reduced insecticide applications. Vip3A is a Bt vegetative insecticidal protein that is active against lepidopterous pests. It has a different mode of action from other proteins for control of Lepidoptera in current Bt crops, and when combined with these proteins, it should help to delay the evolution of pest resistance to Bt crops. This paper presents data on the effects of Vip3A on non-target organisms, and an ecological risk assessment of MIR162 maize, which expresses Vip3Aa20. Laboratory studies indicate few adverse effects of Vip3A to non-target organisms: 11 of 12 species tested showed no adverse effects when exposed to high concentrations of Vip3A relative to estimated exposures resulting from cultivation of MIR162 maize. Daphnia magna exposed to Vip3Aa20 were unaffected in terms of survival or fecundity, but grew slightly more slowly than unexposed controls. The data indicate that cultivation of MIR162 maize poses negligible risk to non-target organisms, and that crops producing Vip3A are unlikely to adversely affect biological control organisms such that benefits from reduced insecticide applications are lost.     

The Chitinase A from the baculovirus AcMNPV enhances resistance to both fungi and herbivorous pests in tobacco

Biotechnology has allowed the development of novel strategies to obtain plants that are more resistant to pests, fungal pathogens and other agents of biotic stress. The obvious advantages of having genotypes with multiple beneficial traits have recently fostered the development of gene pyramiding strategies, but less attention has been given to the study of genes that can increase resistance to different types of harmful organisms. Here we report that a recombinant Chitinase A protein of the Autographa californica nuclear polyhedrosis virus (AcMNPV) has both antifungal and insecticide properties in vitro. Transgenic tobacco plants expressing an active ChiA protein showed reduced damages caused by fungal pathogens and lepidopteran larvae, while did not have an effect on aphid populations. To our knowledge, this is the first report on the characterisation and expression in plants of a single gene that increases resistance against herbivorous pests and fungal pathogens and not affecting non-target insects. The implications and the potential of the ChiA gene for plant molecular breeding and biotechnology are discussed.     

转Bt基因抗虫作物对非靶标害虫的影响

转基因作物的长期大面积种植, 在为农业生产带来惠益的同时, 对农业生态系统的健康和稳定可能会产生潜在的影响。转基因作物表达的Bt蛋白对靶标害虫起到较好的控制效果, 而对Bt蛋白不敏感的非靶标害虫种群可能会迅速发展起来, 对作物造成为害。随着抗虫转基因作物的连续多年种植, 科学家们对于田间杀虫剂施用量的增减看法不尽一致。通过总结已有的研究报道, 本文以Bt玉米和Bt棉花为例, 分析了大田中非靶标害虫暴发的现状, 以及暴发的主要原因(如杀虫剂的使用、害虫天敌减少和物种替代)。在生产实践中, 抗虫作物的长期大面积释放导致广谱杀虫剂施用量减少, 田间非靶标害虫数量上升。因此今后需要继续开展更多的研究来综合评估种植转Bt基因作物产生的长期潜在影响, 优化害虫防治措施, 避免非靶标害虫暴发。     

The roles of olfaction and vision in host-plant finding by the diamondback moth, Plutella xylostella

Abstract.  The relative roles of olfaction and vision in the crepuscular host-finding process of a major lepidopteran pest of cruciferous crops, the diamondback moth Plutella xylostella are investigated in a series of laboratory and semi‐field experiments. Flying female moths use volatile plant chemical cues to locate and to promote landing on their host, even in complex mixed-crop environments in large cages. Multiple regression analysis shows that both the plant position (front, middle or back rows) and the type of plant (host plant, nonhost plant) are needed to explain the distribution of insects in such a mixed-crop situation. This strong plant position effect indicates that, when host plants are present in a mixture, foraging P. xylostella are more likely to alight on the first row of the plants. The findings are discussed with regard to current theories of host-plant location by phytophagous insects and the possible implications for integrated pest management.     

植食性昆虫对植物的反防御机制

本文综述了植食性昆虫对植物的反防御机制.一方面,植食性昆虫可通过其快速进化的寄主选择适应性,改变取食策略,调节生长发育的节律,以及规避自然天敌等抑制、逃避或改变植物的防御,即行为防御机制;另一方面,植食性昆虫可适应植物蛋白酶抑制剂、逃避植物防御伤信号、解毒植物次生物质,以及抑制植物阻塞反应来对植物防御进行反防御,即生理和生化防御机制.其中,昆虫抑制植物伤信号,防止植物阻塞反应是反防御机制的研究热点.昆虫反防御的研究有助于提高对昆虫-植物间协同进化关系的认识,并为害虫治理和抗虫植物的培育提供新的思路.     

植物挥发性物质对昆虫作用的研究进展

不同植物的挥发性物质对昆虫行为有着不同的调节作用,部分对害虫表现为引诱作用,部分对害虫表现为驱避和致死作用,有的则表现为寄主植物与天敌昆虫之间的互惠引诱定位作用。本文综述了近年国内外有关植物挥发性物质的研究概况及其对昆虫的不同作用,展望了其在未来害虫综合治理中的应用。     

转Bt基因水稻秸秆降解对土壤微生物可培养类群的影响

以高抗螟虫、已释放应用的 Bt水稻 (克螟稻 1号 )及其亲本 (非 Bt水稻 )为材料 ,在实验室条件下研究了转 Bt基因水稻及其亲本秸秆在降解过程中对土壤微生物主要类群的影响 ,这些类群包括细菌、真菌、放线菌、反硝化细菌、解磷微生物。结果表明 :(1)降解过程中 Bt蛋白浓度在前两周内迅速下降 ,随后降解速度变慢 ,17d以后至 5 3d,Bt蛋白浓度基本上保持在 6 .72 8～6 .196 ng/ g的水平。 (2 )秸秆降解过程中 ,不同处理细菌数量的变化趋势相似 ,转基因水稻与其亲本之间差异显著 ,非转基因细菌数量高于转基因细菌数量。(3)除降解初期第 3天、第 6天之外 ,其他取样时期的转基因水稻真菌数量要显著高于非转基因和对照。(4)放线菌数量没有明显变化规律 ,除第 6、9、2 6、35天外 ,非转基因数量显著高于转基因。(5 )非转基因秸秆降解反硝化细菌活性高于转基因 ,而解磷微生物活性处理之间无明显差异。     

A fusion protein containing a lepidopteran-specific toxin from the South Indian red scorpion (Mesobuthus tamulus) and snowdrop lectin shows oral toxicity to target insects

Background  

Despite evidence suggesting a role in plant defence, the use of plant lectins in crop protection has been hindered by their low and species-specific insecticidal activity. Snowdrop lectin (Galanthus nivalis agglutinin; GNA) is transported to the haemolymph of insects after oral ingestion, and can be used as a basis for novel insecticides. Recombinant proteins containing GNA expressed as a fusion with a peptide or protein, normally only toxic when injected into the insect haemolymph, have the potential to show oral toxicity as a result of GNA-mediated uptake.