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Construction of a hypervirulent and specific mycoinsecticide for locust control.

Fang W, Lu HL, King GF, St Leger RJ - Sci Rep (2014)

Bottom Line: We found that expression of four insect specific neurotoxins improved the efficacy of M. acridum against acridids by reducing lethal dose, time to kill and food consumption.Coinoculating recombinant strains expressing AaIT1(a sodium channel blocker) and hybrid-toxin (a blocker of both potassium and calcium channels), produced synergistic effects, including an 11.5-fold reduction in LC50, 43% reduction in LT50 and a 78% reduction in food consumption.However, specificity was retained as the recombinant strains did not cause disease in non-acridids.

View Article: PubMed Central - PubMed

Affiliation: Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou. 310058, Zhejiang, China.

ABSTRACT
Locusts and grasshoppers (acridids) are among the worst pests of crops and grasslands worldwide. Metarhizium acridum, a fungal pathogen that specifically infects acridids, has been developed as a control agent but its utility is limited by slow kill time and greater expense than chemical insecticides. We found that expression of four insect specific neurotoxins improved the efficacy of M. acridum against acridids by reducing lethal dose, time to kill and food consumption. Coinoculating recombinant strains expressing AaIT1(a sodium channel blocker) and hybrid-toxin (a blocker of both potassium and calcium channels), produced synergistic effects, including an 11.5-fold reduction in LC50, 43% reduction in LT50 and a 78% reduction in food consumption. However, specificity was retained as the recombinant strains did not cause disease in non-acridids. Our results identify a repertoire of toxins with different modes of action that improve the utility of fungi as specific control agents of insects.

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Food consumption by uninfected grasshoppers and grasshoppers infected by wild-type or transgenic M. acridum.The food consumption of grasshoppers infected by a fungal strain was shown as the quotient (ratio of food consumption) achieved by dividing the amount of feces produced by infected grasshoppers by that of the uninfected controls, so the ratio of food consumption of the uninfected control is always 1 at different time points. Uninfected controls: uninfected grasshoppers; WT: wild-type strain; AaIT1 and Hybrid are transformants expressing AaIT1 and hybrid-toxin, respectively. AaIT1/Hybrid: a 1:1 combination of transformants AaIT1 and hybrid-toxin.
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f4: Food consumption by uninfected grasshoppers and grasshoppers infected by wild-type or transgenic M. acridum.The food consumption of grasshoppers infected by a fungal strain was shown as the quotient (ratio of food consumption) achieved by dividing the amount of feces produced by infected grasshoppers by that of the uninfected controls, so the ratio of food consumption of the uninfected control is always 1 at different time points. Uninfected controls: uninfected grasshoppers; WT: wild-type strain; AaIT1 and Hybrid are transformants expressing AaIT1 and hybrid-toxin, respectively. AaIT1/Hybrid: a 1:1 combination of transformants AaIT1 and hybrid-toxin.

Mentions: Since prevention of feeding damage is of primary importance in assessing agronomic efficacy, we compared fecal production (dry weight) by grasshoppers as an estimate of food consumption. Compared to uninfected grasshoppers (controls), fecal production by grasshoppers infected by fungi started to decline 3 days after inoculation. As expected, the percent reduction compared to uninfected insects increased sharply with time (Fig. 4). The transgenic strains all reduced feeding of grasshoppers to a significantly greater extent than the wild-type strain (P < 0.05). After 7 days, fecal production by grasshoppers infected by 1,000 conidia/insect of the wild-type, 324-AaIT1, 324-HYBRID and the 324-HYBRID/324-AaIT1 combination was reduced by 53%, 65%, 67% and 78%, respectively, compared to the uninfected control grasshoppers. These reductions are significantly different for the wild-type and transgenic strains, and between the 324-HYBRID and 324-AaIT1/324-HYBRID combination (P < 0.001). AaIT1 and hybrid-toxin reduced fecal production to a similar extent (P = 0.52), but differentially effected grasshopper behavior. The bodies of grasshoppers killed by the wild-type, 324-AaIT1, 324-Hv1a or 324-Hv1c were dispersed randomly in their containers. In contrast, within three days of infection, grasshoppers infected by 324-HYBRID or 324-HYBRID/324-AaIT1 were located mostly on the wet cotton balls, and 43% died on these balls.


Construction of a hypervirulent and specific mycoinsecticide for locust control.

Fang W, Lu HL, King GF, St Leger RJ - Sci Rep (2014)

Food consumption by uninfected grasshoppers and grasshoppers infected by wild-type or transgenic M. acridum.The food consumption of grasshoppers infected by a fungal strain was shown as the quotient (ratio of food consumption) achieved by dividing the amount of feces produced by infected grasshoppers by that of the uninfected controls, so the ratio of food consumption of the uninfected control is always 1 at different time points. Uninfected controls: uninfected grasshoppers; WT: wild-type strain; AaIT1 and Hybrid are transformants expressing AaIT1 and hybrid-toxin, respectively. AaIT1/Hybrid: a 1:1 combination of transformants AaIT1 and hybrid-toxin.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256560&req=5

f4: Food consumption by uninfected grasshoppers and grasshoppers infected by wild-type or transgenic M. acridum.The food consumption of grasshoppers infected by a fungal strain was shown as the quotient (ratio of food consumption) achieved by dividing the amount of feces produced by infected grasshoppers by that of the uninfected controls, so the ratio of food consumption of the uninfected control is always 1 at different time points. Uninfected controls: uninfected grasshoppers; WT: wild-type strain; AaIT1 and Hybrid are transformants expressing AaIT1 and hybrid-toxin, respectively. AaIT1/Hybrid: a 1:1 combination of transformants AaIT1 and hybrid-toxin.
Mentions: Since prevention of feeding damage is of primary importance in assessing agronomic efficacy, we compared fecal production (dry weight) by grasshoppers as an estimate of food consumption. Compared to uninfected grasshoppers (controls), fecal production by grasshoppers infected by fungi started to decline 3 days after inoculation. As expected, the percent reduction compared to uninfected insects increased sharply with time (Fig. 4). The transgenic strains all reduced feeding of grasshoppers to a significantly greater extent than the wild-type strain (P < 0.05). After 7 days, fecal production by grasshoppers infected by 1,000 conidia/insect of the wild-type, 324-AaIT1, 324-HYBRID and the 324-HYBRID/324-AaIT1 combination was reduced by 53%, 65%, 67% and 78%, respectively, compared to the uninfected control grasshoppers. These reductions are significantly different for the wild-type and transgenic strains, and between the 324-HYBRID and 324-AaIT1/324-HYBRID combination (P < 0.001). AaIT1 and hybrid-toxin reduced fecal production to a similar extent (P = 0.52), but differentially effected grasshopper behavior. The bodies of grasshoppers killed by the wild-type, 324-AaIT1, 324-Hv1a or 324-Hv1c were dispersed randomly in their containers. In contrast, within three days of infection, grasshoppers infected by 324-HYBRID or 324-HYBRID/324-AaIT1 were located mostly on the wet cotton balls, and 43% died on these balls.

Bottom Line: We found that expression of four insect specific neurotoxins improved the efficacy of M. acridum against acridids by reducing lethal dose, time to kill and food consumption.Coinoculating recombinant strains expressing AaIT1(a sodium channel blocker) and hybrid-toxin (a blocker of both potassium and calcium channels), produced synergistic effects, including an 11.5-fold reduction in LC50, 43% reduction in LT50 and a 78% reduction in food consumption.However, specificity was retained as the recombinant strains did not cause disease in non-acridids.

View Article: PubMed Central - PubMed

Affiliation: Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou. 310058, Zhejiang, China.

ABSTRACT
Locusts and grasshoppers (acridids) are among the worst pests of crops and grasslands worldwide. Metarhizium acridum, a fungal pathogen that specifically infects acridids, has been developed as a control agent but its utility is limited by slow kill time and greater expense than chemical insecticides. We found that expression of four insect specific neurotoxins improved the efficacy of M. acridum against acridids by reducing lethal dose, time to kill and food consumption. Coinoculating recombinant strains expressing AaIT1(a sodium channel blocker) and hybrid-toxin (a blocker of both potassium and calcium channels), produced synergistic effects, including an 11.5-fold reduction in LC50, 43% reduction in LT50 and a 78% reduction in food consumption. However, specificity was retained as the recombinant strains did not cause disease in non-acridids. Our results identify a repertoire of toxins with different modes of action that improve the utility of fungi as specific control agents of insects.

Show MeSH
Related in: MedlinePlus