Hitting back at superpests

日期:2019-02-26 04:11:01 作者:蔡黻聆 阅读:

By Bob Holmes A SEEMINGLY unimportant bacterial toxin could give a new lease of life to a “natural” insecticide by delaying the evolution of resistance in the pests it kills. The insecticide, called Bt, is a cocktail of compounds known as Cry toxins made by the bacterium Bacillus thuringiensis. It is harmless to most other animals, but as Bt use has boomed, some insects have become resistant. The Cry toxins may have a new ally, however. Some strains of B. thuringiensis, which make a class of Cry toxins called CryIV, also produce a toxin called CytA. By itself, CytA is not very poisonous, but it makes CryIV much more potent. Margaret Wirth and her colleagues at the University of California at Riverside exposed mosquito larvae to CryIV and CytA alone and in combination. For mosquito strains that showed no resistance to CryIV, the researchers found that adding CytA made CryIV three to seven times as toxic. But for resistant mosquito strains, the effect was far greater: CytA boosted CryIV’s killing power up to 70-fold (Proceedings of the National Academy of Sciences, vol 94, p 10 536). CryIV toxins kill only mosquitoes, blackflies and their kin. Wirth will now test whether CytA can overcome resistance to other classes of Cry toxin used against beetles and moth larvae. “The applicability beyond CryIV remains to be seen,