Expression of murine adenosine deaminase (ADA) in transgenic maize

A murine adenosine deaminase (ADA) gene, driven by the maize ubi-1 promoter and intron region, was transformed into embryogenic maize callus, along wi th a bar and gusA gene-containing plasmid, using microparticle bombardment. Selection in the presence of either the herbicide Basta(R) or the adenosin e analogue 2'-deoxyadenosine resulted in transgenic cultures that expressed GUS and accumulated a 41-kD protein that immunoprecipated with an ADA-spec ific polyclonal antibody. ADA enzyme activity was observed in extracts from transgenic callus as well as regenerated plants and progeny. Cultures expr essing ADA grew in the presence of 200mg/l 2'-deoxyadenosine, a concentrati on which completely inhibited the growth of non-transgenic cultures. ADA ac tivity appeared to segregate in progeny of regenerated plants as a single, dominant Mendelian trait. These results suggest that ADA, in combination wi th adenosine analogue selection, represents a potentially viable selectable marker system for transgenic maize production.