Genetic Transformation Using Maize Immature Zygotic Embryos
Epidermal and subepidermal cells in the abaxial, basal region of the maize (Zea mays L.) immature zygotic embryo (IZE) scutellum can be induced by exogenous auxin to proliferate and undergo somatic embryogenesis. Successful genetic transformation of IZEs depends not only on optimizing transformation parameters for these totipotent cells, but also on achieving high embryogenic callus induction frequency (ECIF) in a population of targeted explants. In maize, ECIF is strongly influenced by genotype, the tissue culture media used, and the interaction of these two factors. Altering tissue culture media components to increase ECIF and/or transformation frequency (TF) has been one approach used to expand the range of maize genotypes amenable to genetic transformation using the IZE. This chapter outlines such an approach – an Agrobacterium-mediated transformation protocol is used for direct-targeting IZEs of the hybrid Hi Type II and inbred B104 lines. Two different media regimes are used for successful culture and transformation of two distinct genotypes.
Key wordsAgrobacterium tumefaciens B104 Callus induction frequency Embryogenic callus Genetic transformation Hi II Immature zygotic embryo Maize
Our thanks to Jennifer McMurray and Tina Paque for their contributions in the laboratory and greenhouse, and to Dr. Arnel Hallauer for providing the original B104 seed. This work is supported partially by the National Science Foundation (DBI #0110023), the Iowa State University Agricultural Experiment Station, the Office of Biotechnology, the Plant Science Institute, and the Baker Endowment Advisory Council for Excellence in Agronomy at Iowa State University.
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