Expression of a Bacillus thuringiensis cry1Ab gene in transgenic white spruce and its efficacy against the spruce budworm (Choristoneura fumiferana)
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A synthetic version of the cry1Ab gene from Bacillus thuringiensis (Bt) was introduced into white spruce (Picea glauca) by microprojectile bombardment. A plasmid carrying the cry1Ab gene, driven by a ubiquitin (maize) promoter, was co-transferred with a plasmid containing the gus–nptII fusion gene as a screenable selection marker. Molecular analysis of the transgenic lines showed a high level (more than 90%) of co-integration of the cry1Ab gene with the screenable marker. A wide range of expression levels of the cry1Ab gene and corresponding endotoxin was obtained. Accumulation of the Cry1Ab protein was evaluated in embryogenic tissue, the needles of somatic seedlings and in the needles of 5-year-old field-grown trees of individual lines. Laboratory and field insect feeding trials suggest that several spruce transgenic lines were lethal to spruce budworm larvae.