Genetic transformation of maize cells by particle bombardment.

Intact maize cells were bombarded with microprojectiles bearing plasmid DNA coding for selectable (neomycin phosphotransferase [NPT II]) and screenable (beta-glucuronidase [GUS]) marker genes. Kanamycin-resistant calli were selected from bombarded cells, and these calli carried copies of the NPT II and GUS genes as determined by Southern blot analysis. All such calli expressed GUS although the level of expression varied greatly between transformed cell lines. These results show that intact cells of important monocot species can be stably transformed by microprojectiles.