Wheat transformed with a high-molecular-weight glutenin gene showed
irregular expression of glutenin and changed its expression levels over
subsequent generations.
Manipulated Organism:
Spring wheat (Triticum aestivum L.), cultivar Bobwhite.
Inserted Transgenes:
A novel "hybrid" high molecular-weight glutenin subunit (HMW-GS)
gene for producing glutenin, created by fusing two native wheat genes. To
facilitate gene expression, the resulting gene was fused to a native wheat
promoter.
Goal:
Increase the amount of glutenin stored in wheat kernels. Glutenin
is a protein important for the elasticity of wheat dough used for
baking. Researchers hope to improve the baking quality of wheat flour.
Target Effect:
Wheat plants, cultivated over four generations in greenhouse experiments,
did express transgenic glutenin.
Nontarget Effects:
-
The transgenic lines were detected by their resistance to the herbicide
bialaphos (the gene for the herbicide was part of the inserted transgene
construct). Of the 26 lines in which resistance was detected, 7 (31%) did
not accumulate transgenic glutenin in their seeds, although theoretically
they should have.
-
In 4 of the 15 lines (27%) that were cultivated over four generations,
there was a loss or reduction in the expression levels of the transgenic
glutenin.
-
The line that expressed the most transgenic glutenin also synthesized
less than normal amounts of native (endogenous) glutenin, which may be
due to transgene suppression by the host organism (see below).
Additional Comments:
In connection with the last item mentioned under nontarget effects, the
authors note: "Decreases in expression of homologous endogenous genes
are often seen in transgenic plants when related genes are introduced
into the genome. Further experiments are in progress to test whether or
not the decline in endogenous HMW-GS accumulation in this unusual line is
due to some type of transgene-mediated suppression. If this is the case,
it means that additional gene copies can result in either an increase or
a decrease in total HMW-GS content. The latter might be desirable in wheat
varieties in which reduced dough elasticity would be useful" (p. 878).
Source:
Blechl, A. and O. Anderson (1996). "Expression of a Novel
High-Molecular-Weight Glutenin Subunit Gene in Transgenic Wheat,"
Nature Biotechnology 14: 875-9.
Author Affiliations:
USDA, Agricultural Research Service (ARS).
Funding:
ARS.
Product Status:
Not on the market as of 2008.
Copyright 2008 The Nature
Institute.
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