Occasional loss of expression of phosphinothricin tolerance in sexual offspring of transgenic oilseed rape (Brassica napus L.) |
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Authors: | Peter LJ Metz Evert Jacobsen Willem J Stiekema |
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Institution: | (1) DLO-Centre for Plant Breeding and Reproduction Research (CPRO-DLO), Department of Molecular Biology, P.O. Box 16, 6700 AA Wageningen, The Netherlands;(2) Graduate School of Experimental Plant Sciences, Department of Plant Breeding, Wageningen Agricultural University, Lawickse Allee 166, 6709 DB Wageningen, The Netherlands |
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Abstract: | The commercial and economic value of genetically modified crops is determined by a predictable, consistent and stable transmission
and expression of the transgenes in successive generations. No gene inactivation is expected after selfings or crosses with
non-transformed plants of homozygous transgenic oilseed rape plants if the expression of the transgene in homozygous or hemizygous
nature in such plants is stable. The segregation ratios of phosphinothricin (PPT) tolerance in successive generations of selfings
and mutual crosses of a few independent transgenic PPT-tolerant oilseed rape plants indicated a dominant, monogenic inheritance.
In within-variety and between-variety crosses no transgene inactivation was observed. However, after selfings and backcrosses
with non-transgenic oilseed rape infrequent loss of the expression of the PPT tolerance transgene was observed independent
from its homozygous or hemizygous nature. Molecular analysis of PPT-susceptible plants showed that the loss of expression
was due to gene inactivation and not to the absence of the transgene. Methylation and co-suppression are mechanisms that might
cause reduced or even loss of expression of the transgene in later generations. The implications of this observation for seed
multiplication of varieties and breeding activities with transgenic oilseed rape are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | biosafety gene inactivation phosphinothricin tolerance gene transgenic Brassica napus |
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