Wound-inducible expression of the Bacillus thuringiensis Cry1B gene in transgenic rice

摘要

To investigate whether wound-induced production of Cry endotoxin protects transgenic rice against striped stem borer (SSB), we prepared constructs bearing a synthetic cry1B coding sequence controlled by the promoter region of either the constitutive maize ubiquitin gene or wound-inducible maize genes--the maize proteinase inhibitor gene (mpi) and the hydroxyproline-rich glycoprotein (hrgp) gene. The mpi-cry1B-nos and Ubi-cry1B-nos gene cassettes on the one hand and the hrgp-cry1B-nos and Ubi-cry1B-nos gene cassettes on the other hand were cloned in pBKS+ vectors and pCAMBIAlSOO binary vectors, respectively, for microprojectile bombardment- and Agrobacten'um-mediated transformation of cv. Ariete. Accumulation of cry1B from an undetectable level to 0.2% of total soluble protein, 8-12 h after mechanical wounding, was demonstrated in leaf and pith tissues of lines harboring the pmpi-cry1B construct. In these plants, cry1B was not detected in pollen, endosperm, and embryo, unlike in pUbi-cry1B plants. Two out of 43 pmpi-cry1B plants were found to exhibit full protection against SSB damage. Seventeen and 66 plants harboring the Hrgp-cry1B and Ubi-cry1B T-DNA, respectively, were obtained through co-culture of embryogenic calli with strain EHA105. Some 58.8% and 42.2% of Hrgp-cry1B and Ubi-cry1B plants, respectively, accumulated Cry1B above 0.1% total soluble protein in leaf tissue. Wound-stimulated expression of cry1B was demonstrated in young leaf tissue of most Hrgp-cry1B plants.