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A toxin-binding alkaline phosphatase fragment synergizes Bt toxin Cry1Ac against susceptible and resistant Helicoverpa armigera.

Chen W, Liu C, Xiao Y, Zhang D, Zhang Y, Li X, Tabashnik BE, Wu K - PLoS ONE (2015)

Bottom Line: Reduced activity and reduced transcription of an alkaline phosphatase protein that binds Cry1Ac was associated with resistance to Cry1Ac in the four most resistant strains.Although synergism of Bt toxins against susceptible insects by toxin-binding fragments of cadherin and aminopeptidase N has been reported previously, the results here provide the first evidence of synergism of a Bt toxin by a toxin-binding fragment of alkaline phosphatase.The results here also provide the first evidence of synergism of a Bt toxin by any toxin-binding peptide against resistant insects.

View Article: PubMed Central - PubMed

Affiliation: The State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing, 100193, China.

ABSTRACT
Evolution of resistance by insects threatens the continued success of pest control using insecticidal crystal (Cry) proteins from the bacterium Bacillus thuringiensis (Bt) in sprays and transgenic plants. In this study, laboratory selection with Cry1Ac yielded five strains of cotton bollworm, Helicoverpa armigera, with resistance ratios at the median lethal concentration (LC50) of activated Cry1Ac ranging from 22 to 1700. Reduced activity and reduced transcription of an alkaline phosphatase protein that binds Cry1Ac was associated with resistance to Cry1Ac in the four most resistant strains. A Cry1Ac-binding fragment of alkaline phosphatase from H. armigera (HaALP1f) was not toxic by itself, but it increased mortality caused by Cry1Ac in a susceptible strain and in all five resistant strains. Although synergism of Bt toxins against susceptible insects by toxin-binding fragments of cadherin and aminopeptidase N has been reported previously, the results here provide the first evidence of synergism of a Bt toxin by a toxin-binding fragment of alkaline phosphatase. The results here also provide the first evidence of synergism of a Bt toxin by any toxin-binding peptide against resistant insects.

No MeSH data available.


Related in: MedlinePlus

Relative ALP transcription detected by qRT-PCR in susceptible and resistant H. armigera larvae.Different letters above the error bars indicate significant differences between means (P<0.05).
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pone.0126288.g002: Relative ALP transcription detected by qRT-PCR in susceptible and resistant H. armigera larvae.Different letters above the error bars indicate significant differences between means (P<0.05).

Mentions: Relative to a susceptible strain (96S), laboratory selection yielded resistance ratios based on the median lethal concentration (LC50) of activated Cry1Ac ranging from 22 to 1700 in five strains of H. armigera (Table 1). Reduced ALP activity and transcription were associated with resistance to Cry1Ac in the four most resistant strains (LF10, LF30, LF60, and LF120), but not in the least resistant of the five selected strains (LF5) (Figs 1 and 2). ALP activity and transcription did not differ significantly between LF5 and the susceptible strain, but LF10, LF30, LF60 and LF120 had significantly lower ALP activity and transcription than the susceptible strain (Figs 1 and 2). As expected, ALP activity and ALP transcription were positively associated across all observations for the six susceptible and resistant strains of H. armigera (linear regression, F1, 34 = 58.6, R2 = 0.63, P < 0.0001). The resistance ratio for Cry1Ac activated toxin (log-transformed) was negatively associated with mean ALP activity across the six susceptible and resistant strains (linear regression, F1, 4 = 35.1, R2 = 0.90, P = 0.004). APN activity did not vary significantly among the six strains (Fig 3).


A toxin-binding alkaline phosphatase fragment synergizes Bt toxin Cry1Ac against susceptible and resistant Helicoverpa armigera.

Chen W, Liu C, Xiao Y, Zhang D, Zhang Y, Li X, Tabashnik BE, Wu K - PLoS ONE (2015)

Relative ALP transcription detected by qRT-PCR in susceptible and resistant H. armigera larvae.Different letters above the error bars indicate significant differences between means (P<0.05).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4401514&req=5

pone.0126288.g002: Relative ALP transcription detected by qRT-PCR in susceptible and resistant H. armigera larvae.Different letters above the error bars indicate significant differences between means (P<0.05).
Mentions: Relative to a susceptible strain (96S), laboratory selection yielded resistance ratios based on the median lethal concentration (LC50) of activated Cry1Ac ranging from 22 to 1700 in five strains of H. armigera (Table 1). Reduced ALP activity and transcription were associated with resistance to Cry1Ac in the four most resistant strains (LF10, LF30, LF60, and LF120), but not in the least resistant of the five selected strains (LF5) (Figs 1 and 2). ALP activity and transcription did not differ significantly between LF5 and the susceptible strain, but LF10, LF30, LF60 and LF120 had significantly lower ALP activity and transcription than the susceptible strain (Figs 1 and 2). As expected, ALP activity and ALP transcription were positively associated across all observations for the six susceptible and resistant strains of H. armigera (linear regression, F1, 34 = 58.6, R2 = 0.63, P < 0.0001). The resistance ratio for Cry1Ac activated toxin (log-transformed) was negatively associated with mean ALP activity across the six susceptible and resistant strains (linear regression, F1, 4 = 35.1, R2 = 0.90, P = 0.004). APN activity did not vary significantly among the six strains (Fig 3).

Bottom Line: Reduced activity and reduced transcription of an alkaline phosphatase protein that binds Cry1Ac was associated with resistance to Cry1Ac in the four most resistant strains.Although synergism of Bt toxins against susceptible insects by toxin-binding fragments of cadherin and aminopeptidase N has been reported previously, the results here provide the first evidence of synergism of a Bt toxin by a toxin-binding fragment of alkaline phosphatase.The results here also provide the first evidence of synergism of a Bt toxin by any toxin-binding peptide against resistant insects.

View Article: PubMed Central - PubMed

Affiliation: The State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing, 100193, China.

ABSTRACT
Evolution of resistance by insects threatens the continued success of pest control using insecticidal crystal (Cry) proteins from the bacterium Bacillus thuringiensis (Bt) in sprays and transgenic plants. In this study, laboratory selection with Cry1Ac yielded five strains of cotton bollworm, Helicoverpa armigera, with resistance ratios at the median lethal concentration (LC50) of activated Cry1Ac ranging from 22 to 1700. Reduced activity and reduced transcription of an alkaline phosphatase protein that binds Cry1Ac was associated with resistance to Cry1Ac in the four most resistant strains. A Cry1Ac-binding fragment of alkaline phosphatase from H. armigera (HaALP1f) was not toxic by itself, but it increased mortality caused by Cry1Ac in a susceptible strain and in all five resistant strains. Although synergism of Bt toxins against susceptible insects by toxin-binding fragments of cadherin and aminopeptidase N has been reported previously, the results here provide the first evidence of synergism of a Bt toxin by a toxin-binding fragment of alkaline phosphatase. The results here also provide the first evidence of synergism of a Bt toxin by any toxin-binding peptide against resistant insects.

No MeSH data available.


Related in: MedlinePlus