Plant Cell, Vol. 10, 1603-1622, October 1998, Copyright © 1998, American Society of Plant Physiologists
Ribozymes Targeted to Stearoyl–ACP 
9 Desaturase mRNA Produce Heritable Increases of Stearic Acid in Transgenic Maize Leaves
Ann Owens Merloa,
Neil Cowena,
Tom Delateb,
Brent Edingtonb,
Otto Folkertsc,
Nicole Hopkinsa,
Christine Lemeiuxb,
Tom Skokuta,
Kelley Smitha,
Aaron Woosleya,
Yajing Yangb,
Scott Younga, and
Michael Zwickb
a Biotechnology and Plant Genetics Department, Dow AgroSciences, 9330 Zionsville Road, Indianapolis, Indiana 46268
b Ribozyme Pharmaceuticals Inc., 2950 Wilderness Place, Boulder, Colorado 80301
c CuraGen Corporation, Eleventh Floor, 555 Long Wharf Drive, New Haven, Connecticut 06511
Correspondence to:
Michael Zwick, mgzwick{at}rpl.com (E-mail), 303-449-6995 (fax).
Ribozymes are RNAs that can be designed to catalyze the specific cleavage or ligation of target RNAs. We have explored the possibility of using ribozymes in maize to downregulate the expression of the stearoyl–acyl carrier protein (9) desaturase gene. Based on site accessibility and catalytic activity, several ribozyme constructs were designed and transformed into regenerable maize lines. One of these constructs, a multimer hammerhead ribozyme linked to a selectable marker gene, was shown to increase leaf stearate in two of 13 maize lines. There were concomitant decreases in 9 desaturase mRNA and protein. The plants with the altered stearate phenotype were shown to express ribozyme RNA. The ribozyme-mediated trait was heritable, as evidenced by stearate increases in the leaves of the R1 plants derived from a high-stearate line. The increase in stearate correlated with the presence of the ribozyme gene. A catalytically inactive version of this ribozyme did not produce any significant effect in transgenic maize. This is evidence that ribozymes can be used to modulate the expression of endogenous genes in maize.
