Is the mature endotoxin Cry1Ac from Bacillus thuringiensis inactivated by a coagulation reaction in the gut lumen of resistant Helicoverpa armigera larvae?

Ma, Gang; Roberts, Harry; Sarjan, Muhammad; Featherstone, Nicki; Lahnstein, Jelle; Akhurst, Raymond J.; Schmidt, Otto

doi:10.1016/j.ibmb.2005.02.011

Cited by 116 publications

(97 citation statements)

References 30 publications

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“…Significantly increased midgut esterase activity and elevated immune response have been reported to be associated with Bt resistance in some Lepidoptera pests (43,46,47). Determination of esterase activity in midgut lysate from T. ni larvae from the Cornell strain and the GLENCry2Ab-BCS8 strain showed that there was no difference in midgut esterase activities between the resistant and susceptible larvae (Fig.…”

Section: Resultsmentioning

confidence: 88%

Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism

Song

Kain

Cassidy

et al. 2015

Appl Environ Microbiol

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The resistance to the Bacillus thuringiensis (Bt) toxin Cry2Ab in a greenhouse-originated Trichoplusia ni strain resistant to both Bt toxins Cry1Ac and Cry2Ab was characterized. Biological assays determined that the Cry2Ab resistance in the T. ni strain was a monogenic recessive trait independent of Cry1Ac resistance, and there existed no significant cross-resistance between Cry1Ac and Cry2Ab in T. ni. From the dual-toxin-resistant T. ni strain, a strain resistant to Cry2Ab only was isolated, and the Cry2Ab resistance trait was introgressed into a susceptible laboratory strain to facilitate comparative analysis of the Cry2Ab resistance with the susceptible T. ni strain. Results from biochemical analysis showed no significant difference between the Cry2Ab-resistant and -susceptible T. ni larvae in midgut proteases, including caseinolytic proteolytic activity and zymogram profile and serine protease activities, in midgut aminopeptidase and alkaline phosphatase activity, and in midgut esterases and hemolymph plasma melanization activity. For analysis of genetic linkage of Cry2Ab resistance with potential Cry toxin receptor genes, molecular markers for the midgut cadherin, alkaline phosphatase (ALP), and aminopeptidase N (APN) genes were identified between the original greenhouse-derived dual-toxin-resistant and the susceptible laboratory T. ni strains. Genetic linkage analysis showed that the Cry2Ab resistance in T. ni was not genetically associated with the midgut genes coding for the cadherin, ALP, and 6 APNs (APN1 to APN6) nor associated with the ABC transporter gene ABCC2. Therefore, the Cry2Ab resistance in T. ni is conferred by a novel but unknown genetic mechanism.T he Gram-positive soil bacterium Bacillus thuringiensis (Bt) has been widely used as a microbial insecticide in sprayable formulations, and Bt toxins are the primary insecticidal proteins expressed in genetically engineered crops to confer insect resistance (1; ISAAA's GM Approval Database, http://www.isaaa.org /gmapprovaldatabase/). Since the mid-1990s, insect-resistant Bt crops have been rapidly adopted with proven economic and environmental benefits (2, 3). However, development of insect resistance to Bt toxins threatens the long-term success of application of Bt toxins for insect pest control. The genetic potential of insect populations to evolve Bt resistance has been well shown in laboratory selections, and cases of insect resistance to Bt formulations and Bt crops have occurred in insect populations under selection pressure by Bt sprays and Bt crops in the field (4-8).Studies of insect resistance to Bt toxins have so far been mostly on Lepidoptera pests to the toxin Cry1Ab or Cry1Ac (9-19), the two major Bt Cry toxins which are highly toxic to Lepidoptera pests and known to share the same binding sites in target insects (4, 20). Cry1Ab and Cry1Ac are the primary insecticidal proteins expressed in the current commercial transgenic Bt maize and Bt cotton varieties to target Lepidoptera pests in the field (21). Resistance to Cry1Ac and Cry1Ab ...

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Section: Resultsmentioning

confidence: 88%

Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism

Song

Kain

Cassidy

et al. 2015

Appl Environ Microbiol

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“…To date, phenoloxidase activity has been considered in three other species with resistance to Bt: Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), Helicoverpa armigera (Hü bner) (Lepidoptera: Noctuidae), and Trichoplusia ni (Hü bner) (Lepidoptera: Noctuidae) (Rahman et al 2004, Ma et al 2005, Wang et al 2007). For both E. kuehniella and H. armigera, Bt resistance was associated with higher phenoloxidase activity (Rahman et al 2004, Ma et al 2005. However, some data suggest that higher phenoloxidase activity does not cause greater Bt resistance (Rahman et al 2007).…”

Section: Discussionmentioning

confidence: 99%

“…Melanization occurs by the action of the prophenoloxidase pathway ) and differences in the level of phenoloxidase activity could contribute to differences in susceptibility to pathogens between Bt-resistant and Bt-susceptible genotypes. Additionally, resistance to Bt toxin has been associated with increased phenoloxidase activity in some species (Rahman et al 2004, Ma et al 2005 but not others (Wang et al 2007), although it is unknown whether these Bt-resistant genotypes show altered susceptibility to entomopathogenic nematodes. Altogether, it is reasonable to hypothesize that Bt resistance might result in either an increase or decrease in phenoloxidase activity.…”

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confidence: 99%

Effects of Pink Bollworm Resistance to <I>Bacillus thuringiensis</I> on Phenoloxidase Activity and Susceptibility to Entomopathogenic Nematodes

Gassmann¹,

Fabrick²,

Sisterson³

et al. 2009

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Widespread planting of crops genetically engineered to produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) imposes selection on many key agricultural pests to evolve resistance to Bt. Fitness costs can slow the evolution of Bt resistance. We examined effects of entomopathogenic nematodes on fitness costs of Bt resistance in the pink bollworm,Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), a major pest of cotton,Gossypium hirsutum L., in the southwestern United States that is currently controlled by transgenic cotton that produces Bt toxin Cry1Ac. We tested whether the entomopathogenic nematodes Steinernema riobrave Cabanillas, Poinar, and Raulston (Rhabditida: Steinernematidae) and Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) affected fitness costs of resistance to Cry1Ac in two laboratory-selected hybrid strains of pink bollworm reared on non-Bt cotton bolls. The nematode S. riobrave imposed a recessive fitness cost for one strain, and H. bacteriophora imposed a fitness cost affecting heterozygous resistant individuals for the other strain. Activity of phenoloxidase, an important component of insects' immune response, did not differ between Bt-resistant and Bt-susceptible families. This suggests phenoloxidase does not affect susceptibility to entomopathogenic nematodes in Bt-resistant pink bollworm. Additionally, phenoloxidase activity does not contribute to Bt resistance, as has been found in some species. We conclude that other mechanisms cause higher nematode-imposed mortality for pink bollworm with Bt resistance genes. Incorporation of nematode-imposed fitness costs into a spatially explicit simulation model suggests that entomopathogenic nematodes in non-Bt refuges could delay resistance by pink bollworm to Bt cotton. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. ABSTRACT Widespread planting of crops genetically engineered to produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) imposes selection on many key agricultural pests to evolve resistance to Bt. Fitness costs can slow the evolution of Bt resistance. We examined effects of entomopathogenic nematodes on Þtness costs of Bt resistance in the pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), a major pest of cotton, Gossypium hirsutum L., in the southwestern United States that is currently controlled by transgenic cotton that produces Bt toxin Cry1Ac. We tested whether the entomopathogenic nematodes Steinernema riobrave Cabanillas, Poinar, and Raulston (Rhabditida: Steinernematidae) and Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) affected Þtness costs of resistance to Cry1Ac in two laboratory-selected hybrid strains of pink bollworm reared on non-Bt cotton bolls. The nematode S. riobrave imposed a recessive Þtness cost for one strain, and H. bacteriophora imposed a Þtness cost affec...

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“…Similarly, toxin sequestration by esterases or hexamerins in the host gut fluids that prevented advancement of the intoxication process have been associated to Cry1Ac-tolerance in Helicoverpa armigera (Gunning et al, 2005;Ma et al, 2005). The existence of similar sequestering mechanisms in digestive fluids of other insects needs to be explored.…”

Section: Specificity Level Iv: Toxin Sequestrationmentioning

confidence: 99%

Specificity determinants for Cry insecticidal proteins: Insights from their mode of action

Jurat-Fuentes

Crickmore

2017

Journal of Invertebrate Pathology

151

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Is the mature endotoxin Cry1Ac from Bacillus thuringiensis inactivated by a coagulation reaction in the gut lumen of resistant Helicoverpa armigera larvae?

Cited by 116 publications

References 30 publications

Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism

Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism

Effects of Pink Bollworm Resistance to <I>Bacillus thuringiensis</I> on Phenoloxidase Activity and Susceptibility to Entomopathogenic Nematodes

Specificity determinants for Cry insecticidal proteins: Insights from their mode of action

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