TRANSFORMATION OF 12 DIFFERENT PLASMIDS INTO SOYBEAN VIA PARTICLE BOMBARDMENT

Particle bombardment offers a simple method for the introduction of DN A into plant cells. Multiple DNA fragments may be introduced on a sing le plasmid or on separate plasmids (co-transformation). To investigate some of the properties and limits of co-transformation, 12 different plasmids were introduced into embryogenic suspension culture tissue of soybean [Glycine max (L.) Merrill] via particle bombardment. The DNAs used for co-transformation included 10 plasmids containing RFLP marke rs for maize and 2 plasmids separately encoding hygromycin-resistance and beta-glucuronidase. Two weeks following bombardment with the 12 di fferent plasmids, suspension culture tissue was placed under hygromyci n selection. Hygromycin-resistant clones were isolated after an additi onal 5 to 6 weeks. Southern hybridization analysis of 26 hygromycin-re sistant embryogenic clones verified the presence of introduced plasmid DNAs. All of the co-transforming plasmids were present in most of the transgenic soybean clones and there was no preferential uptake and in tegration of any of the plasmids. The copy number of individual plasmi ds was approximately equal within clones but highly variable between c lones. While some clones contained as few as zero to three copies of e ach plasmid; others clones contained as many as 10 to 15 copies of eac h of the 12 different plasmids.