Phytoparasitica (1997) 25, 351-352
M. Keller, B. Sneh, N. Strizhov, Avital Regev, Szuszanna Koncz-Kalman, C. Koncz, J. Schell and Aviah Zilberstein (1997)
Transgenic plants containing the Bt gene cry1C for controlling polyphagous insects of the genus Spodoptera
Phytoparasitica 25 (4), 351-352
Japan-Israel Workshop on Novel Approaches for Controlling Insect Pests and Plant Diseases, July 12-17, 1997, Kibbutz Ma'ale haHamisha, Israel
Abstract: Species of the genus Spodoptera are widespread in the subtropical and tropical zones of the world. They are relatively resistant to insecticides and cause severe crop losses. Cry1C and Cry1E delta-endotoxins, produced by several Bacillus thuringiensis strains, are capable of interacting with specific receptors of the gut epithelium of Spodoptera species and then forming membrane ion channels that destroy the electrolytic balance leading to the rupture of epithelial cells and larval mortality. While all the individuals of the examined larval population of Spodoptera littoralis possess Cry1C receptors, Cry1E receptors are present only in a certain portion of the population. Therefore, to obtain a consistent insecticidal effect, the study was focused on the use of cry1C as the main insecticidal transgene. Enhanced toxicity was obtained by co-applying Escherichia coli - produced Cry1C (756aa) and ChiAII endochitinase to young larvae of S. littoralis. ChiAII is encoded by the Serratia marcescens chiAII gene and capable of perforating the chitin-containing peritrophic membrane lining the lumen of the insect gut. The pores increase the availability of the toxin molecules to the epithelial receptors. The 3' truncated cry1C linked to the 35S promoter with four tandemly arranged 35S enhancers and chiAII driven by the mannopine synthase P2 promoter were introduced into tobacco and alfalfa via Agrobacterium-mediated gene transfer. Transgenic alfalfa carrying the two transgenes was found to be more resistant to young larvae of S. littoralis than plants with only cry1C. However, the level of cry1C transcripts in the relatively resistant plants was below the detection capacity of Northern analysis. To improve cry1C expression in plants, a plant-like cry1C gene was synthesized by a templatedirected ligation of 5'-phosphorylated primers and specific PCR amplification. In this synthetic cry1C, 249 out of 630 codons were modified and the G+C content was raised from 36% to 45%. The synthetic cry1C was barely expressed in E. coli but strongly expressed in transgenic plants, when linked to the 35S promoter with the four enhancers. Transgenic alfalfa, tobacco and potato expressed approximately 0.001-0.2% Cry1C and were fully tolerant to all larval instars of S. littoralis and S. exigua. All the transgenic plants were also resistant to the non-selective herbicide 'Basta' (glufosinate-ammonium) dictated by the introduced pat gene and therefore can be directly integrated into routine breeding programs. Since S. littoralis is the more tolerant species of Spodoptera to delta-endotoxins, it is plausible to assume that these transgenics are resistant also to the rest of the Spodoptera species.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Baruch Sneh
Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
genetical engin./transgenic plants
molecular biology - genes
