Efficacy of Transgenic Cotton Containing a cry1Ac Gene from Bacillus thuringiensis Against Helicoverpa armigera (Lepidoptera: Noctuidae) in Northern China

Wu, Kongming; Guo, Yong; Lv, Nan; Greenplate, John T.; Deaton, Randy W.

doi:10.1093/jee/96.4.1322

Cited by 46 publications

(42 citation statements)

References 11 publications

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“…These factors may account for the lack of unequivocal field evidence of enhanced resistance to Bt cotton containing Cry1Ac in the People's Republic of China. However, it must be noted that the efficacy of Bt cotton against the cotton bollworm decreases with plant aging and thus there are some survivors in B. thuringiensis fields in the late season (31). This lower efficacy of Bt cotton later in the season may favor the survival of heterozygotes (rs).…”

Section: Discussionmentioning

confidence: 99%

Disruption of a Cadherin Gene Associated with Resistance to Cry1Ac δ-Endotoxin of Bacillus thuringiensis in Helicoverpa armigera

2005

Appl Environ Microbiol

280

248

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A laboratory strain (GY) of Helicoverpa armigera (Hübner) was established from surviving larvae collected from transgenic cotton expressing a Bacillus thuringiensis var. kurstaki insecticidal protein (Bt cotton) in Gaoyang County, Hebei Province, People's Republic of China, in 2001. The GYBT strain was derived from the GY strain through 28 generations of selection with activated Cry1Ac delivered by diet surface contamination. When resistance to Cry1Ac in the GYBT strain increased to 564-fold after selection, we detected high levels of cross-resistance to Cry1Aa (103-fold) and Cry1Ab (>46-fold) in the GYBT strain with reference to those in the GY strain. The GYBT strain had a low level of cross-resistance to B. thuringiensis var. kurstaki formulation (Btk) (5-fold) and no cross-resistance to Cry2Aa (1.4-fold). Genetic analysis showed that Cry1Ac resistance in the GYBT strain was controlled by one autosomal and incompletely recessive gene. The cross-resistance pattern and inheritance mode suggest that the Cry1Ac resistance in the GYBT strain of H. armigera belongs to "mode 1," the most common type of lepidopteran resistance to B. thuringiensis toxins. A cadherin gene was cloned and sequenced from both the GY and GYBT strains. Disruption of the cadherin gene by a premature stop codon was associated with a high level of Cry1Ac resistance in H. armigera. Tight linkage between Cry1Ac resistance and the cadherin locus was observed in a backcross analysis. Together with previous evidence found with Heliothis virescens and Pectinophora gossypiella, our results confirmed that the cadherin gene is a preferred target for developing DNA-based monitoring of B. thuringiensis resistance in field populations of lepidopteran pests.

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Section: Discussionmentioning

confidence: 99%

Disruption of a Cadherin Gene Associated with Resistance to Cry1Ac δ-Endotoxin of Bacillus thuringiensis in Helicoverpa armigera

2005

Appl Environ Microbiol

280

248

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“…during the growing season, particularly from flowering onwards (Greenplate et al 1998). It was reported that toxins to helicoverpa armigera in leaves of a commercial Chinese cotton variety GK-12 that contains Cry1Ac were significantly decreased as the crop approached maturation (Wu et al 2003), while insecticidal protein levels in GK-19, a transgenic Bt cotton cultivar carrying a Cry1Ac/Cry1Ab fused gene, were higher during the early stages of cotton growth and significantly declined hereafter, behaving more variably than in GK-12 during the whole period of cotton growth and development (Wan et al 2005).…”

Section: Spatio-temporal Expression Of Insecticidal Genesmentioning

confidence: 99%

Variation in the spatio-temporal expression of insecticidal genes in cotton

Bakhsh¹,

Shahzad²,

Husnain³

2011

Czech J. Genet. Plant Breed.

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Abstract:The most significant breakthrough in plant biotechnology is the development of the techniques to transform genes from unrelated sources into commercially important crop plants to develop resistance against targeted insect pests. The spatio-temporal expression of insecticidal genes in transgenic cotton varies with plant age, plant parts and environmental conditions. The understanding of this temporal and spatial variation in efficacy and the resulting mechanisms is essential for cotton protection and production. This review summarizes variations in the efficacy of introduced insecticidal genes in cotton crop. The factors contributing to the variability of endotoxins have also been highlighted. The reduction in Bt protein biosynthesis in late-season cotton tissues could be attributed to the overexpression of the Bt gene at earlier stages, which leads to gene regulation at post-transcription levels and consequently results in gene silencing at a later stage. Methylation of the promoter may also play a role in the declined expression of endotoxin proteins. In genetically modified crops several environmental factors have been reported to affect the expression of transgenes. Among environmental factors nitrogen metabolism, inhibition of synthesis, degradation, remobilization and high temperature are attributable to the quantitative reduction in Bt proteins. Applying plant growth regulators or protein enhancers such as Chaperone TM may improve Bt cotton efficacy through enhancing the synthesis of proteins. Also some agronomic practices such as nitrogen fertilization and timely irrigation favour the endotoxin expression. Thus, variations in the efficacy of insecticidal genes in transgenic cotton and the involved mechanisms need to be understood fully so as to plan rational resistance management strategies to retard the rate of resistance development and to control target pests effectively by enhancing the endotoxin expression through genetic or agronomic management.

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“…Transgenic Bt cotton that expresses the Cry1Ac toxin is highly effective against the major lepidopterous cotton insect pests [9]. Multiple field trials have proven that Bt cotton exhibits high insecticidal efficacy against larvae of tobacco budworm, cotton bollworm and other target lepidopterous pests and decreases the population densities of these target pest species in cotton fields [10][11][12]. However, the evolution of resistance or tolerance to Bt toxins by herbivorous insects is a serious threat to the efficacy of Bt-based insecticides and toxin-producing transgenic plants, which are generally pest specific and environmentally safe [13,14].…”

mentioning

confidence: 99%

Temporal allocation of metabolic tolerance to transgenic Bt cotton in beet armyworm, Spodoptera exigua (Hübner)

Guo

Wan

2011

Sci. China Life Sci.

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Digestive and detoxification enzyme activity and nutrient composition were examined in the body of fourth instar beet armyworms, Spodoptera exigua (Hübner), fed on transgenic Bacillus thuringiensis (Bt) and non-Bt cotton for different time periods. Nutrient composition and specific enzyme activities differed significantly between the S. exigua fed Bt vs. non-Bt cotton. At 1, 6 and 24 h, free fatty acid and glucose levels were significantly lower in S. exigua fed on Bt cotton than those fed on non-Bt cotton. S. exigua fed on Bt cotton had significantly higher trypsin and total superoxide dismutase (T-SOD) activities and significantly lower lipase, carboxylesterase and acetylcholinesterase activities than non-Bt fed worms for all feeding time periods. Differences were also observed among feeding times within each cotton variety group. Significantly lower free fatty acid and total amino acid were observed in S. exigua fed on Bt cotton for 24 h than in those fed for 1 h. Significantly lower activities of lipase and trypsin were detected in S. exigua fed on Bt cotton for 24 h than those for 1 and 4 h. However, carboxylesterase and acetylcholinesterase activities in S. exigua fed on Bt cotton for 24 h were significantly higher than those for 1, 4 and 6 h. The interaction between cotton variety and feeding time significantly affected the activities of lipase, trypsin, acetylcholinesterase and T-SOD enzymes in S. exigua. Measuring the temporal allocation of protection and detoxification enzyme activities in the body of S. exigua in response to B. thuringiensis can provide a meaningful evaluation on the metabolic tolerance of herbivorous insects under the continuous selection pressure of a toxic protein.

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Efficacy of Transgenic Cotton Containing a cry1Ac Gene from Bacillus thuringiensis Against Helicoverpa armigera (Lepidoptera: Noctuidae) in Northern China

Cited by 46 publications

References 11 publications

Disruption of a Cadherin Gene Associated with Resistance to Cry1Ac δ-Endotoxin of Bacillus thuringiensis in Helicoverpa armigera

Disruption of a Cadherin Gene Associated with Resistance to Cry1Ac δ-Endotoxin of Bacillus thuringiensis in Helicoverpa armigera

Variation in the spatio-temporal expression of insecticidal genes in cotton

Temporal allocation of metabolic tolerance to transgenic Bt cotton in beet armyworm, Spodoptera exigua (Hübner)

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