Insect-resistant cotton

The cotton line 3006-210-23 was genetically engineered to resist attack from lepidopteran insect pests such as the cotton bollworm, pink bollworm, tobacco budworm, beet armyworm, and soybean looper. This insect resistance is conferred by the cry1Ac gene, originally isolated from the common soil bacterium Bacillus thuringiensis (Bt) var. kurstaki.

Line 'Germain's Acala GC510'

pMYC3006

Coding sequences of Cry1A(c) and pat genes altered for optimal expression in plant cells.

Southern blot analysis demonstrated that event 3006-210-23 contains a single integration of the transgenic DNA, including one intact copy of the cry1Ac gene, one intact copy of the pat gene, and single, intact copies of each of the regulatory elements. Analysis also indicated that there was no integration of segments from the erythromycin resistance gene.

The cry1Ac gene produces the insect control protein Cry1Ac, a delta-endotoxin, in the plant tissues. Cry proteins, of which Cry1Ac is only one, act by selectively binding to specific sites localized on the lining of the midgut of susceptible insect species. Following binding, pores are formed that disrupt midgut ion flow, causing gut paralysis and eventual death due to bacterial sepsis. Cry1Ac is insecticidal only when eaten by the larvae of lepidopteran insects (moths and butterflies), and its specificity of action is directly attributable to the presence of specific binding sites in the target insects. There are no binding sites for delta-endotoxins of B. thuringiensis on the surface of mammalian intestinal cells, therefore, livestock animals and humans are not susceptible to these proteins.