TOXICITY AND BINDING-PROPERTIES OF THE BACILLUS-THURINGIENSIS DELTA-ENDOTOXIN CRY1C TO CULTURED INSECT CELLS

A better understanding of the mode of action of Bacillus thuringiensis delta-endotoxins is needed to develop strategies which may prevent or slow down selection for resistance. We studied the effect of Cry1C on several different cultured insect cell lines by means of toxicity ass ays, ligand blotting, and toxin binding studies. A clear difference in sensitivity toward Cry1C between the insect cell lines was observed. Spodoptera frugiperda cell line Sf9 was most sensitive, whereas Spodop tera exigua cell lines SeUCR and SelZD2109 showed intermediate sensiti vity. Mamestra brassicae (Mb0503) and Drosophila melanogaster (Dm1) ce lls were the least sensitive as compared to Sf9 cells. Ligand blot ana lysis of SDS-PAGE size-separated proteins showed that Cry1C specifical ly binds to a 40-kDa protein in Sf9, SeUCR, and SelZD2109 cells. Cry1A b does not bind to this protein. The Cry1C-binding protein was not obs erved in Mb0503 and Dm1 cells, suggesting that the presence of the 40- kDa Cry1C-binding protein is correlated with sensitivity toward Cry1C. (C) 1998 Academic Press.