PLANT PHYSIOLOGY , Vol 107, Issue 2 469-477, Copyright © 1995 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Repression of Acetolactate Synthase Activity through Antisense Inhibition (Molecular and Biochemical Analysis of Transgenic Potato (Solanum tuberosum L. cv Desiree) Plants)
R. Hofgen, B. Laber, I. Schuttke, A. K. Klonus, W. Streber and H. D. Pohlenz
Hoechst Schering AgrEvo GmbH, D-13476 Berlin, Germany
Acetolactate synthase (ALS), the first enzyme in the biosynthetic pathway
of leucine, valine, and isoleucine, is the biochemical target of different
herbicides. To investigate the effects of repression of ALS activity
through antisense gene expression we cloned an ALS gene from potato
(Solanum tuberosum L. cv Desiree), constructed a chimeric antisense gene
under control of the cauliflower mosaic virus 35S promoter, and created
transgenic potato plants through Agrobacterium tumefaciens-mediated gene
transfer. Two regenerants revealed severe growth retardation and strong
phenotypical effects resembling those caused by ALS-inhibiting herbicides.
Antisense gene expression decreased the steady-state level of ALS mRNA in
these plants and induced a corresponding decrease in ALS activity of up to
85%. This reduction was sufficient to generate plants almost inviable
without amino acid supplementation. In both ALS antisense and
herbicide-treated plants, we could exclude accumulation of 2-oxobutyrate
and/or 2-aminobutyrate as the reason for the observed deleterious effects,
but we detected elevated levels of free amino acids and imbalances in their
relative proportions. Thus, antisense inhibition of ALS generated an in
vivo model of herbicide action. Furthermore, expression of antisense RNA to
the enzyme of interest provides a general method for validation of
potential herbicide targets.
