Genetically Transformed Maize (Zea mays L.) Plants from Protoplasts
Agriculturally important cereal crops, including maize, have been difficult to engineer genetically using current techniques for gene insertion. With few exceptions (Graves and Goldman 1986; Grimsley et al. 1987), most of the graminaceous crops are not readily susceptible to infection by Agrobacterium tumefaciens, which is a vector for gene transfer commonly used with many dicot species. Genes can be transferred directly into protoplasts, without an Agrobacterium vector, by methods that permit DNA to cross the plasmalemma (Krens et al. 1982; Shillito et al. 1985; Riggs and Bates 1986; Fromm et al. 1986). Stable transformation of maize cells has been achieved through direct uptake of DNA into protoplasts that had been permeabilized by electroporation (Fromm et al. 1986; Pierce et al. 1987), but until recently (Rhodes et al. 1988 a), no plants had been recovered from maize protoplasts. We now describe regeneration of maize plants derived from protoplasts into which a gene encoding neomycin phosphotransferase II (NPT II) was introduced via electroporation. NPT II permits plant cells to grow on inhibitory levels of the antibiotic kanamycin (Fraley et al. 1983; Fromm et al. 1986) and can be used as a dominant marker to select for transformed cells. Following is the account of our published work on the regeneration of transformed plants from maize protoplasts (Rhodes et al. 1988 b).
KeywordsMaize Plant Maize Streak Virus Relative Specific Activity Maize Protoplast Black Mexican Sweet
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