NEWS OF ΤΉΕ WEEK
DNA TECHNOLOGY Bacterial gene works in plant cell Functioning genes have been moved successfully from bacteria into plant cells, marking an important mile stone on the way to using recombinant-DNA technology to engineer and improve plants genetically. Though similar successes have been hinted at previously, those ef forts often failed to pan out. Now, however, the announcements made during the annual Miami Winter Symposium by Monsanto research ers and a European team of plant molecular biologists are being called "the most definitive so far." The Monsanto group includes Robert Horsch, Stephen G. Rogers, and Rob ert T. Fraley, all of whom are mem bers of the St. Louis-based chemical company's molecular biology group, w h i c h is directed by Ernest G.
Jaworski. The European group at Max-Planck Institute in Cologne, West Germany, and at the Universi ty of Gent, Belgium, is directed by Jeff Schell and Marc Van Montagu. Both the U.S. and the European groups have moved genes that code for antibiotic resistance from bacte ria into plant cells. In the Monsan to case, the gene that inactivates t h e antibiotic k a n n a m y c i n was placed into petunia cells growing in vitro. Ordinarily, those antibiot ics don't affect plants, but they can interfere with the growth of plant cells in vitro. Key to this achievement is the method used for transferring such genes. Overall, they are introduced into plant cells by the Ti plasmid, a circular molecule of DNA from the
Gene-transfer technique uses chimeric gene
Antibiotic resistance gene isolated from lab bacterium
Antibiotic resistance gene, gene signals, and plasmid DNA joined to make chimeric gene Chimeric gene inserted into plant bacterium Plant bacterium DNA
Gene signals for plant cells Plasmid DNA opened with enzyme
Natural DNA exchange
Plasmid DNA isolated from lab bacterium :
ΙΘΒρΐ^-^^^
• H R
Plant cells with chimeric gene can grow in presence of antibiotic
6
January 24, 1983 C&EN
Plant bacterium introduces its DNA and chimeric gene into plant DNA
bacterium Agrobacter tumefaciens, which can infect many plants and give them tumors (C&EN, Juite 22, 1981, page 33). Properly manipu lated, however, that plasmid be comes a useful means for bringing genes from elsewhere into plant cells. Simply putting genes anywhere along the Ti plasmid is not good enough to ensure those genes will work once they're transferred into plant cells. The foreign genes must be attached to a "promoter region" along the Ti plasmid—that is, a part of the DNA that controls adjacent genes. The Monsanto and Europe an g r o u p s thus hooked up the antibiotic-resistance genes to pro moters that ordinarily control syn thesis of an unusual amino acid whose manufacture is tied intimate ly to how Agrobacter establishes it self as a parasite in plant tissues. Though the genes for antibiotic resistance c o n v i n c i n g l y can be moved into plant cells and can func tion there, there is no certitude that those cells can be made to grow into intact plants. Equally, if not more, important, it's not known whether those genes will then con tinue to function once inside intact plants. An answer to the first uncer tainty could be obtained "in a mat ter of months," according to Monsanto's Jaworski. The other prob lem of controlling gene function in selected plant tissues could take much longer. The ability to move genes for an tibiotic resistance offers a convenient way of marking the progress of a gene-transfer procedure. Furthermore, these recently de veloped methods ought to work for transferring genes for valuable traits, such as resistance to diseases, herbi cides, or insects, according to Ja worski. •
