ABSTRACT
On the basis of the results of hybridological analysis, it was established that significant differences in the stability of manifestation of the nptII gene expression are observed between the Nu5 and Nu6 lines obtained from the same initial Nu21 transformant (in spite of the identical genetic environment). Relatively stable expression of the marker gene is registered in the Nu5 line; the frequencies of detection of mosaic descendants are not high. The Nu6 line is characterized by a high frequency of the appearance of mosaic plants (up to 100%), indicating an increase in the marker gene inactivation in this line. When combining the nptII gene alleles in the hybrid genome, the allele coming from the Nu6 line was manifested as semidominant and had a suppressing effect on the allele coming from the Nu5 line. No transinactivation phenomena at the level of phenotype were detected during the interaction of the nptII gene alleles from the Nu5 and Nu6 lines in diheterozygote with the alleles of homologous genes inactivated at the transcriptional or post-transcriptional levels. During segregation to F2, separation of the Nu21 line progeny into two independent groups with preservation of the different character of the marker gene expression (with a moderate level of appearance of mosaic plants for the Nu5 line and with high level for the Nu6 line) was again registered. Further studies are directed to detection of the mechanisms leading to the mosaic type of the studied gene manifestation in transgenic plants of the Nu5 and Nu6 lines.
Subject(s)
Gene Expression Regulation, Plant , Mosaicism , Nicotiana , Plant Proteins , Plants, Genetically Modified , Transgenes , Plant Proteins/biosynthesis , Plant Proteins/genetics , Plants, Genetically Modified/genetics , Plants, Genetically Modified/metabolism , Nicotiana/genetics , Nicotiana/metabolismABSTRACT
The review describes the phenomenon of mosaic transgene (gene) expression in plants. Parallels with the mosaic transgene (gene) expression in other organisms are presented. Parallels with the mosaic patterns of gene (transgene) expression in other organisms (Drosophila, transgenic animals, and others) are made.
Subject(s)
Gene Expression Regulation, Plant , Plants, Genetically Modified , RNA Interference , Transgenes , Animals , Animals, Genetically Modified , Gene Silencing , Protein Biosynthesis , RNA Stability/genetics , RNA, Small Interfering/geneticsABSTRACT
The review presents current data on molecular genetic mechanisms of suppression of the gene (transgene) expression in plants at the transcriptional level. The stages of RNA-directed DNA methylation are discussed in detail. Mutations affecting transcriptional gene inactivation without altering nucleotide sequence methylation are described.
Subject(s)
Gene Expression Regulation, Plant/physiology , Gene Silencing/physiology , Genes, Plant/physiology , Plant Physiological Phenomena , Plants/metabolism , Transcription, Genetic/physiology , Plants/geneticsABSTRACT
A comparative analysis of variability of heterologous gene expression was conducted in original (T0) transgenic tobacco plants, differing with respect to the copy number of uidA gene (a single and two copies as a direct duplication) within the T-DNA insertion, and among progenies obtained by their self-pollination (T1). Variability of beta-glucuronidase enzyme activity was shown in original transgenic plants or among progenies of the first generation in both groups. It is established that the activity level of beta-glucuronidase among T0 plants with a duplication of the uidA gene is significantly higher (21.9 times) than that determined in transformants with a single-copy gene. In T1 progenies of plant 16.40, carrying a duplication of the uidA gene, a drastic decrease in enzyme activity was observed, which correlated with a decrease or absence of mRNA transcripts, pointing to a disturbance in reporter gene expression. Alterations in the functioning of another heterologous gene (nptII) within the same T-DNA insertion were not observed among progenies of transgenic plant 16.40.
Subject(s)
Gene Expression Regulation, Plant , Genes, Plant , Nicotiana/genetics , Plants, Genetically Modified/genetics , Blotting, Southern , DNA Transposable Elements , DNA, Plant/genetics , Gene Duplication , Genes, Reporter , Genetic Markers , Genomic Instability , Glucuronidase/geneticsABSTRACT
The duplication of uidA gene within T-DNA was shown to disturb stability of expression of another marker gene, nptII, in the second generation (T2) of selfed initial transformants and in F1 hybrids of the crosses with nontransgenic tobacco. Hybridological analysis of the progeny resulting from various crosses involving T1 plants demonstrated that the expression of nptII gene was impaired in the hybrids that were hemizygous for the inactivated copy of uidA gene.
