Agrobacterium tumefaciens-Mediated Transformation of Maize Embryos Using a Standard Binary Vector System

Abstract

<p>We have achieved routine transformation of maize (<em>Zea mays</em>) using an <em>Agrobacterium tumefaciens</em>standard binary (non-super binary) vector system. Immature zygotic embryos of the hybrid line Hi II were infected with <em>A. tumefaciens</em> strain EHA101 harboring a standard binary vector and cocultivated in the presence of 400 mg L−1 l-cysteine. Inclusion of l-cysteine in cocultivation medium lead to an improvement in transient β-glucuronidase expression observed in targeted cells and a significant increase in stable transformation efficiency, but was associated with a decrease in embryo response after cocultivation. The average stable transformation efficiency (no. of bialaphos-resistant events recovered per 100 embryos infected) of the present protocol was 5.5%. Southern-blot and progeny analyses confirmed the integration, expression, and inheritance of the <em>bar</em> and<em>gus</em>transgenes in R0, R1, and R2 generations of transgenic events. To our knowledge, this represents the first report in which fertile, stable transgenic maize has been routinely produced using an <em>A. tumefaciens</em>standard binary vector system.</p>