The relationship between homozygous and hemizygous transgene expression levels over generations in populations of transgenic rice plants |
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Authors: | James V A Avart C Worland B Snape J W Vain P |
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Institution: | (1) John Innes Centre, Colney Lane, Norwich NR4 7UH, UK e-mail: philippe.vain@bbsrc.ac.uk Tel: +44-1603-450612, Fax: +44-1603-450045, GB;(2) ENSAT, Avenue de L’Agrobiopole, Auzeville-tolozane, France, FR |
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Abstract: | Segregating T1, T2 and T3 transgenic rice populations, derived from independent particle-bombardment-mediated transformation events were examined in
order to assess the effect of gene dosage on transgene expression levels and stability. The expression level of the unselected
β-glucuronidase (gusA) reporter gene was quantified in plants from these populations. The gusA gene dosage was determined by segregation analysis of progeny seedlings at the structural level (by PCR) and at the expression
level. For some transformation events a gene dosage effect on transgene expression was observed, leading to higher transgene
expression levels in homozygous progeny than in hemizygous progeny or primary transgenic plants. However, in many other transformation
events, the homozygous state appears to be disadvantageous, being associated with lower transgene expression levels, gene
silencing or counter-selection of homozygous plants across generations. Change of gene dosage is probably one of the key factors
influencing transgene expression levels and stability in transgenic rice. This is particularly important when considering
molecular genetic studies and crop improvement programmes. The possible influence of matrix attachment regions (MARs) in increasing
the likelihood of an additive effect on transgene expression level is discussed.
Received: 21 March 2001 / Accepted: 29 June 2001 |
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Keywords: | Rice Transformation Transgene dosage Homozygous Matrix attachment regions (MARs) |
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