Evolution of pest resistance reduces the efficacy of insecticidal proteins from the gram-positive bacterium Bacillus thuringiensis (Bt) used widely in sprays and transgenic crops. Recent efforts to delay pest adaptation to Bt crops focus primarily on combinations of two or more Bt toxins that kill the same pest, but this approach is often compromised because resistance to one Bt toxin causes cr...

Laboratory studies were conducted using ELISA and bioassays (Helicoverpa zea) to investigate temporal Cry protein expression in field-grown single (‘Bollgard’) and dual-toxin (‘Bollgard II’) Bt cotton. In single-toxin Bt cotton, Cry1Ac levels changed significantly as the season progressed, exhibiting ca. 3-fold difference in Cry1Ac expression between the highest date (6.2 ppm—12 June) and the l...

Chilo suppressalis and Sesamia inferens are two important lepidopteran rice pests that occur concurrently during outbreaks in paddy fields in the main rice-growing areas of China. Previous and current field tests demonstrate that the transgenic rice line Huahui 1 (HH1) producing a Cry1Ab-Cry1Ac hybrid toxin from the bacterium Bacillus thuringiensis reduces egg and larval densities of C. suppres...

A major mechanism of resistance to Bacillus thuringiensis (Bt) toxins in Lepidoptera is a reduction of toxin binding to sites in the midgut membrane. Genetic studies of three different species have shown that mutations in a candidate Bt receptor, a 12-cadherin-domain protein, confer Cry1A toxin resistance. Despite a similar resistance profile in a fourth lepidopteran species, Plutella xylostell...

Leaf bioassays and oviposition choice tests were used to investigate the effects of transgenic broccoli expressing Cry1Ac toxin of Bacillus thuringiensis (Berliner) on susceptible and resistant Plutella xylostella (L.) larvae. Survival of susceptible 2nd instars on Cry1Ac-expressing broccoli declined from 99.1 to 19.2% at 24 and 72 h, respectively, and larvae exhibited an average weight loss of...

The Bacillus thuringiensis Cry1Ac delta-endotoxin was shown to bind in a biphasic manner to Manduca sexta aminopeptidase N (APN) present in a novel model membrane. Surface plasmon resonance analysis allowed the quantification of toxin binding to M. sexta APN in a supported lipid monolayer. The initial binding was rapid and reversible, with an affinity constant of 110 nM. The second phase was sl...

This study aimed to determine the influence of vector structure on dual Bt gene expression and establish an efficient expression vector using Cry1Ac and Cry3A genes. Four vectors (N4, N5, N10, and S23) were developed and used for genetic transformation of tobacco to obtain insect-resistant transgenic lines. The vectors were constructed using the MAR structure, applying different promoter and en...

Strains of Bacillus thuringiensis produce insecticidal proteins. These strains have been isolated from diverse ecological niches, such as soil, phylloplane, insect cadavers and grain dust. To effectively propagate, these strains produce a range of molecules that facilitate its multiplication in a competing environment. In this report, we have examined synthesis of a chitin-binding protein and e...

To evaluate resistance to Bacillus thuringiensis Berliner (Bt) toxins, adult female bollworms, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), were collected from four light trap locations in two eastern North Carolina counties from August to October during 2001 and 2002. Females were allowed to oviposit, and upon hatching, 24 neonates from each female (F1 lines) were screened for survival a...

One Bacillus thuringiensis (Bt) and two stacked Bt and cowpea trypsin inhibitor (Bt + CpTI) cottons and their non-transgenic isolines were consecutively cultivated to investigate the soil persistence of Cry1Ac and CpTI proteins and their effects on microbial properties and enzyme activities involving C, N, P, and S cycling in soil. Results showed that there were the persistence of Cry1Ac and Cp...