Bacillus thuringiensis insecticidal crystal toxins: gene structure and mode of action

Thanks to the techniques of recombinant DNA, there is now abundant sequence information on several endotoxin genes of Bacillus thuringiensis. The task of correlating this sequence information with the economically important aspects of the toxins such as insect specificity, LD(50) and speed of kill is now under worldwide investigation. Progress has also been made on understanding the mechanism of action of the toxins and on identifying the parts of the protoxin which are important in toxicity. Taken together, the mechanistic data and the sequence information allow the first attempts at rational design of mutant endotoxin genes and greatly facilitate the transfer of those genes to other organisms such as plants. More information is still needed, however, as to the nature of the binding site of the toxin and on the three-dimensional structure of the activated toxins.     

MALDI-TOF-MS and 16S rRNA characterization of lead tolerant metallophile bacteria isolated from saffron soils of Kashmir for their sequestration potential

Toxic metal contamination in soils due industrialization is nowadays a concern to the scientists worldwide. The current study deals with the evaluation of response and tolerance by isolated metallophilic bacteria in different lead concentrations (100 ppm to 1000 ppm). By taking optical densities of the isolates, the minimum inhibitory concentration (MIC) of Pb²⁺ were determined.16S rRNA and MALDI-TOF MS were used for the identification of the bacteria. Total of 37 isolates were observed, among them 04 (Staphylococcus equorum, Staphylococcus warneri, Bacillus safensis and Bacillus thuringiensis), isolated were detected having efficacy of Pb²⁺tolerance and sequestration at varying MIC. Furthermore, B. thuringiensis was observed to have highest (900 ppm) tolerance for lead and lowest (500 ppm) for Staphylococcus warneri. Moreover, the highest (65.3%) sequestration potential has been observed for B. thuringiensis and least (52.8%) for S. warneri. The tolerance and sequestration potential properties of these isolated species can be utilised to exterminate heavy metals and reduce their toxicity from the contaminated environment.     

南疆三地棉铃虫田间种群对Bt棉的抗性频率监测

为了监测南疆主要Bt棉区棉铃虫田间种群对Bt棉的抗性频率,分别采集库尔勒、阿克苏、泽普三地的棉铃虫单雌系,以Bt毒蛋白作为人工饲料,采用单雌系F1代法进行棉铃虫田间种群抗性个体检测.本文从库尔勒、阿克苏、泽普三地分别筛选了57个、106个、92个棉铃虫单雌系.三地棉铃虫单雌系幼虫在正常饲料和Cry1Ac饲料上的平均发育级别呈线性相关,相对平均发育级别平均值分别为0.5210、0.4935、0.4623,无≥0.8的个体,估测南疆三地棉铃虫种群的Bt抗性基因频率均小于0.001.泽普玉米种植比例较高,可有效稀释棉铃虫种群的Bt抗性基因,因此泽普的棉铃虫种群敏感度最高.本研究可为新疆Bt棉区棉铃虫的抗性治理提供科学依据.     

Zero effect of Bt rice on expression of genes coding for digestion,detoxification and immune responses and developmental performances of Brown Planthopper Nilaparvata lugens (Stål)

Transgenic Cry1Ac, Cry2Aa and Cry1Ca (Bt toxins) rice lines are well developed to manage lepidopteron pests in China. The impact of transgenic Bt rice on the non-target Brown Planthopper (BPH) has become an essential part of environmental risk assessment, however, scanty evidence is found addressing on developmental and molecular responses of BPH to the ingestion of Bt protein from transgenic rice. The focus of the current study is to examine the developmental characteristics and the expression profiles of gene in relation to digestion, detoxification and immune responses were examined. Our study strongly revealed that the tested Bt rice strains have no unfavorable effect on fecundity, survival and growth of BPH. Furthermore, each of the tested genes did not exhibit distinct expression pattern responding to non Bt parental cultivar, thus, it could be concluded that Bt rice have no detrimental effects on the physiological processes of digestion, detoxification and immune responses of BPH.     

Bitrophic toxicity of Cry1Ac to Cycloneda sanguinea,a predator in Brazilian cotton

Insect predators are exposed to the Cry1Ac toxin in Bt cotton fields through several pathways. In this study, we investigated the effects of activated Cry1Ac added to a diet on Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae), which is one of the main predators of non‐target pests in Brazilian cotton. Direct bitrophic exposure of C. sanguinea to Cry1Ac was done by feeding beetles with Aphis gossypii (Glover) (Hemiptera: Aphidae) sprayed with 500 μg per ml Cry1Ac solution. Larval and pupal survival, development time, aphid consumption, and adult longevity were recorded daily. Couples within the same experimental treatment were paired and numbers of eggs laid and hatched per female were recorded daily. Net replacement rate was calculated for each female. During development, a C. sanguinea larva consumed on average 1.8 μg of activated Cry1Ac. No significant differences due to Cry1Ac were observed for any of the response variables, except aphid consumption. Larvae receiving Cry1Ac consumed more aphids than larvae receiving distilled water alone. Additional statistical analyses were conducted to evaluate independence of responses, and for the independent responses, a simple meta‐analysis was conducted to test the null hypothesis that all responses were zero. Nearly all of the response variables were statistically independent. Two pairs of responses were not independent, but the associated multivariate tests were not significant. The meta‐analysis suggested that all effects were not different from random variation around zero and no cumulative effects could be detected. Our results indicated that bitrophic exposure to activated Cry1Ac is likely to have little or no adverse ecological effect on C. sanguinea.     

转Bt基因棉花对烟粉虱天敌昆虫龟纹瓢虫的影响

在实验室控制条件下,以转Bt基因棉花GK12、33B、SGK321上的烟粉虱为食料饲养龟纹瓢虫,研究转Bt基因棉花上的烟粉虱对龟纹瓢虫生长发育及捕食的影响,同时利用Y型嗅觉仪,观察龟纹瓢虫对来自不同类型棉花的棉叶及其烟粉虱的嗅觉反应和视觉反应。结果表明,转Bt基因棉花和对应的常规棉亲本上的烟粉虱对龟纹瓢虫的发育历期和存活率没有明显的影响。龟纹瓢虫对棉花叶片、烟粉虱若虫、蜜露、蜕等4种物质的视觉反应之间没有明显的差异。对4种嗅源物质的嗅觉选择性的大小依次为：烟粉虱若虫＞蜕＞棉花＞蜜露;在两类不同的棉花之间,转基因棉花和常规棉,龟纹瓢虫对GK12、33B、SGK321等三种转基因棉花上的烟粉虱若虫的嗅觉选择性明显较对应的常规棉亲本SM3、33、SY321上的烟粉虱若虫小;对烟粉虱若虫的蜕,两种转单价基因棉花GK12、33B较对应的常规棉亲本上的小,而转双价基因的棉花SGK321上与对应的常规棉之间没有明显的差异。烟粉虱密度大于200头.皿_-1时,龟纹瓢虫捕食转基因棉花上烟粉虱的数量大于对应的常规棉花亲本,但烟粉虱密度小于200头.皿_-1时,龟纹瓢虫捕食转基因棉花上烟粉虱的数量小于对应的常规棉花亲本。龟纹瓢虫对烟粉虱的捕食符合HollingⅡ型反应。龟纹瓢虫取食转基因棉花上的烟粉虱的理论极限值、瞬间攻击率均大于常规棉花。     

Epigeic spiders are not affected by the genetically modified maize MON 88017

The genetically modified (GM) maize MON 88017 facilitates weed management owing to its tolerance to glyphosate, and resists western corn rootworm (WCR), Diabrotica virgifera virgifera, owing to the expression of Cry3Bb1 toxin. MON 88017 could therefore contribute to the solution of two major problems of European agriculture: continuous WCR spreading and high use of herbicides. To assess possible unwanted environmental impacts of MON 88017, we compared communities of spiders in plots planted in three successive years with this maize, its near isogenic non‐GM cultivar treated or not treated with an insecticide and two unrelated maize cultivars. Each of the five treatments was applied on five 0.5 ha plots in a 14 ha field. Spiders were collected in five pitfall traps per plot five times per year. Upon reaching the waxy ripening stage, all plants of first‐year cultivation were shredded to small pieces and ploughed into the soil in the respective plot, whereas in the 2nd and 3rd year the harvest was used for biogas production and only digestate was returned to the field. Out of 79 spider species, Pardosa agrestis, Pachygnatha degeeri and Oedothorax apicatus made up 28%, 25% and 23% of the total spider count in the 1st year of study; 2%, 8% and 84% in the 2nd; and 40%, 8% and 35% in the 3rd year. Statistical analysis did not reveal any influence of GM maize on the spider abundance and biodiversity. The abundance, and in two years also the species diversity, was insignificantly higher on the plots with GM maize than on plots with the insecticide‐treated non‐GM maize. The composition and size of spider community varied year to year, probably reflecting weather conditions and differences in field fertilization with organic matter.     

Genetically modified feeds in animal nutrition 1st communication: Bacillus thuringiensis (Bt) corn in poultry,pig and ruminant nutrition

During the last few years, animal nutrition has been confronted with genetically modified organisms (GMO), and their significance will increase in the future.

The study presents investigations on the substantial equivalence of the transgenic Bt (Bacillus thuringiensis) corn and the corresponding nontransgenic hybrid Cesar and parameters of nutrition physiology such as digestibility and energy content for poultry, pigs and ruminants. The results of the analysed corn samples as well as of the silage samples illustrated substantial equivalence in all investigated ingredients, such as crude nutrients, amino acids, fatty acids, minerals and non‐starch polysaccharides. The results of the experiments using poultry, pigs, wethers and fattening bulls were not influenced by the genetic modification of corn. The determined values for the digestibilities and the energy contents for poultry, pigs and wethers were not affected by the used corn variety. Neither the examined parameters of the fattening experiments with bulls nor the slaughter results showed any significant differences between the bulls fed on silages made from the nontransgenic or transgenic corn.     

Effects of Elevated Carbon Dioxide on the Growth and Foliar Chemistry of Transgenic Bt Cotton

A field study was carried out to quantify plant growth and the foliar chemistry of transgenic Bacillus thuringiensis （Bt） cotton （cv. GK-12） exposed to ambient CO2 and elevated （double-ambient） CO2 for different lengths of time （1, 2 and 3 months） in 2004 and 2005. The results indicated that CO2 levels significantly affected plant height, leaf area per plant and leaf chemistry of transgenic Bt cotton. Significantly, higher plant height and leaf area per plant were observed after cotton plants that were grown in elevated CO2 were compared with plants grown in ambient CO2 for 1, 2 and 3 months in the investigation. Simultaneously, significant interaction between CO2 level x investigating year was observed in leaf area per plant. Moreover, foliar total amino acids were increased by 14%, 13%, 11% and 12%, 14%, 10% in transgenic Bt cotton after exposed to elevated CO2 for 1, 2 or 3 months compared with ambient CO2 in 2004 and 2005, respectively. Condensed tannin occurrence increased by 17%, 11%, 9% in 2004 and 12%, 11%, 9% in 2005 in transgenic Bt cotton after being exposed to elevated CO2 for 1, 2 or 3 months compared with ambient CO2 for the same time. However, Bt toxin decreased by 3.0%, 2.9%, 3.1% and 2.4%, 2.5%, 2.9% in transgenic Bt cotton after exposed to elevated CO2 for 1, 2 or 3months compared with ambient CO2 for same time in 2004 and 2005, respectively. Furthermore, there was prominent interaction on the foliar total amino acids between the CO2 level and the time of cotton plant being exposed to elevated CO2. It is presumed that elevated CO2 can alter the plant growth and hence ultimately the phenotype allocation to foliar chemistical components of transgenic Bt cotton, which may in turn, affect the plant-herbivore interactions.     

Analysis of the bacterial communities of four predatory natural enemies collected from a Northern China Bt cotton field

Predatory natural enemies are major insect species in cotton field ecosystems. Microbes that live inside these insects play essential roles in vital host activities, however, the microbiota of these insects have not been well characterized. In this study, we used Illumina 16S rRNA amplicon sequencing to investigate microbial diversity of the natural enemies Chrysoperla sinica, Harmonia axyridis, Propylaea japonica and Orius similis from a cotton field in northern China. The microbial diversity of C. sinica was low and its dominant bacterial community were Rickettsia (87.78%) and Wolbachia (6.29%). The microbial community of O. similis was more diverse than that of C. sinica. The microbial diversity of H. axyridis and P. japonica was higher, and they had similar dominant phyla, which included Firmicutes, Proteobacteria and Bacteroidetes. Their common dominant bacterial community were Romboutsia, Escherichia-Shigella, Bacteroides, Terrisporobacter, Enterobacter, Lactobacillus, Fusobacterium, Actinobacillus, Sphaerochaeta, Bacteroidales_S24-7_group and Cyanobacteria. This study also forms the basis for further study on the microbiota of natural enemies from different habitats.