COMPARISON OF THE RESPONSE OF MIDGUT EPITHELIAL-CELLS AND CELL-LINES FROM LEPIDOPTERAN LARVAE TO CRYIA TOXINS FROM BACILLUS-THURINGIENSIS

The cytotoxic responses of midgut epithelial cells (MEG) from spruce b udworm (SBW), gypsy moth (GM) and silkworm (SW) larvae were compared w ith the cytotoxic response of lepidopteran cell lines (SF-9, SE-1a, an d CF-1) to CryIA toxins from Bacillus thuringiensis. The MEC from SBW, SW and GM had binding proteins for CryIA(a,b,c) toxins, whereas the l epidopteran cell lines had binding proteins for CryIA(c). Single MEC e xposed to CryI(a,b,c)toxins in a qualitative lawn assay were equally s usceptible to the toxins with a threshold response at about 1 ng, The cell lines were not susceptible to CryIA(a,b) toxins in the dose range tested, but had threshold responses for CryIA(c) of 3.4 ng for SF-9, 50.2 ng for SE-1a and 5.9 ng for CF-1. In the quantitative Live/Dead a ssay, MEC were equally susceptible to CryIA(a,b,c) toxins with a thres hold effect at about 1 ng and a maximum effect at about 10 ng, CF-1 wa s most sensitive to CryIA(c) with a threshold effect at 0.39 ng and a maximal effect at about 1 ng, In contrast, a 25-50 times greater dose of CryIA(a) or CryIA(b) was required to elicit a similar response as C ryIA(c) for CF-1, SF-9 and SE-1a were most susceptible to CryIA(c) wit h a threshold effect observed at about 0.5 ng and maximal effects at a bout 2 ng, SF-9 cells have a threshold and maximum response to CryIA(a ,b) of about 10 ng and 20 ng, respectively, SE-1a cells have a thresho ld and maximal response to CryIA(a,b) of 5 ng and 10 ng, respectively, Intact midgut epithelium exposed to CryIA(a,b,c) toxins had a thresho ld dose of 2 ng for CryIA(b), 10-30 ng for CryIA(a) and 2-30 ng for Cr yIA(c). This study has shown that MEC are affected by a broader spectr um of toxins compared to the lepidopteran larvae and insect cell lines . (C) 1997 Elsevier Science Ltd.