Mosquito larvicidal activity of transgenic Anabaena PCC 7120 expressing toxin genes from Bacillus thuringiensis subsp. israelensis.

Genes encoding the mosquito larvicidal toxins Cry4Aa, Cry11Aa, Cyt1Aa and the regulatory P20 from Bacillus thuringiensis subsp. israelensis were introduced into the nitrogen-fixing, filamentous cyanobacterium Anabaena PCC 7120 for expression under control of two strong promoters P(psbA) and P(A1). The clone pRVE4-ADRC displayed toxicity against fourth-instar larvae of Aedes aegypti, the highest ever achieved in cyanobacteria. It was about 2.5-fold more toxic than the respective clone without cyt1Aa [Wu et al., Appl. Environ. Microbiol. 63 (1997) 4971-4975]. Cyt1Aa synergized the combination of Crys by about five-fold. Consistently, the lethal times exerted by pRVE4-ADRC were also reduced (it killed exposed larvae more quickly). This clone may become a useful biological control agent which reduces the probability of resistance development in the target organisms [Wirth et al., Proc. Natl. Acad. Sci. USA 94 (1997) 10536-10540].