This article was published in the 3rd issue of Orman ve Av Magazine in 2011; available by citing the source.
In genetic modification of plants, the desired phenotype is tried to be produced by adding a certain gene or genes to a plant or by deactivating a gene. Plants obtained by adding gene are called “transgenic” plants. If the genetic modification is made by using the genes of the plant from the same species or a species that can be crossed with that plant species, using their own "promoter" (¹), the resulting plant is called a "cisgenic" plant. Isolated gene for transfer is called "cisgene".
Transgene is the oldest molecularly isolated gene type for genetic modification in plant breeding. Plant species cannot be crossed and whose sources are mainly viruses or bacteria can also be used as source. For this reason, while the gene pool of “transgenic” organisms is being expanded by human hands, the gene transferred in “cisgenic” organisms has already been present for hundreds of years in individuals of the same or closely crossable species; for this reason, the gene pools of these creatures are not altered. In this sense, it can be said that the "cisgenic" application and the traditional breeding method are equivalent.
Within each plant group, some individuals will grow faster, some will be taller, some will be more voluminous, and some will be more resistant to diseases or drought. Once researchers find which genes cause these differences, they can take those genes from that plant and pass them on to others.
The plant, in which the desired characteristics are transferred through genetic modification (modification), can be produced more quickly than in conventional breeding practices, because most of the genome of the plant is not changed. The application covers only one or a few genes, not the entire genome of the plant's gene pool. “Cisgenic” is an application of genetic engineering conceptually similar to conventional plant breeding. In "cisgenic" practice, genes of closely related species are used. For example, genes are not taken from a bird or roe deer and transplanted into a poplar tree; The gene taken from the same or another type of poplar tree is transferred to the poplar tree again.
Forestry researchers from Oregon State University have shown that the growth rate and other characteristics of trees can be altered by the application of "cisgenic". According to the findings published in the "Plant Biotechnology Journal", the functions of gibberellic acid, a hormone found in poplar trees, were affected by the "cisgenic" application, and significant changes were observed in the wood characteristics, morphology and growth rates of the seedlings. In the greenhouse environment, some poplars were allowed to grow rapidly and some to grow slowly.
The history of modern plant breeding dates back to the late 1800s, in which systematic progeny tests were made to obtain improved characteristics such as rapid growth, desired properties for various purposes, resistance to drought and diseases. The same basic operation applies to 'cisgenic', but with one difference: 'cisgenic' application requires genome and biotechnology techniques that the plant breeders of the time could not even imagine.
Legal regulations regarding the process of Genetically Modified Organisms (GMOs) consider traditional breeding as a basis. If, in practice, such as the European Union's directive numbered 2001/18/EC, the current international regulations on GMOs are focused on “transgenic” applications, and they ensure that only large companies can work on GMOs. Cisgenic studies may be interrupted if the legislation not modified in a way that will specify the distinction between “cisgenic” and “transgenic”.
“Cisgenic” and “Intragenic”
It can be seen that the terms “cisgenic” and “intragenic” are used synonymously. However, there is a fundamental difference between "intragenic" and "cisgenic" practices.
This difference is related to regulatory elements. In “cisgenic” the gene has its own “promoter”(¹), “intron”(²) and “terminator”. In "intragenic", new code sequences and "promotors" are made, there are no requirements such as introns or terminators. "Intragenic" only requires the inheritance of genetic elements from a sexually compatible group. “Cisgenes” are genes belonging to the gene pool that has existed for thousands of years and traditional plant breeders are also using, and “intragens” are new combinations formed from functional parts of genes in the same gene pool. These combinations do not occur naturally and are unlikely to occur spontaneously or as a result of conventional breeding.
(¹) Promoter: A portion of DNA that facilitates the transcription (transcription) of genes. It is located just before/above the point at which a gene begins to be read. Promoters are generally located next to the gene with which they interact and on the same strand. The replication process starts at the "promoter" (initiator) region of the DNA and ends at the "terminator" region.
(²) Intron: It is the part of the DNA that is skipped without being read during replication.
REFERENCES
- Oregon State University. "Success with 'cisgenics' in forestry offers new tools for biotechnology." ScienceDaily 15 June 2010
- http://www.sciencedaily.com/releases/2010/06/100608135116.htm
- Schouten, Henk J., Frans A Krens & Evert Jacobsen Cisgenic plants are similar to traditionally bred plants: EMBO reports 7, 750 - 753 (2006).
- http://www.nature.com/embor/journal/v7/n8/full/7400769.html
- E. Jacobsen & H. J. Schouten “Cisgenesis, a New Tool for Traditional Plant Breeding, Should be Exempted from the Regulation on Genetically Modified Organisms in a Step by Step Approach” Potato Research Volume 51, Number 1, 75-88, DOI: 10.1007/s11540-008-9097-y
- Henk J. Schouten1 and Evert Jacobsen, “Cisgenesis and intragenesis, sisters in innovative plant breeding” Trends in Plant Science, Volume 13, Issue 6, 260-261, 1 June 2008
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