Plant improvement involves the genetic modification of plants through genetic material transfer from one organism to another to produce a desired trait. Two major examples of many ‘transgene’ products are virus-resistant transgenic cotton and beta-carotene-enhanced gold rice. When an alien DNA is introduced into a host organism, the natural defence mechanism of the organism is activated to suppress or silence the expression of this foreign genetic material. This ‘silencing’ process has been the focus of many scientists and researchers to help break through the compatibility limitation of the global agricultural industry.
The conventional understanding of the gene silencing mechanism was that a protein called ‘RNA Polymerase V’ exists across the genome and monitors different sections of DNA to identify the regions that need silencing. It was established that DNA methylation takes place once the RNA Polymerase V identifies a specific area to silence the gene. However, research led by Keith Slotkin, PhD, a Principal Investigator at the Donald Danforth Plant Science Center, presented a new understanding of how DNA methylation occurs. The research suggests that, instead of the presence of RNA Polymerase V protein, the presence of small RNA, which recruits the RNA Polymerase V and directs it to a specific gene, triggers the silencing of that region. “Our model is saying that small RNAs are driving RNA Polymerase V to the new location in the first place. If we get rid of the small RNA machinery, RNA Polymerase V doesn’t know where to go,” Slotkin described.
The research team is also working on the most effective ways to prevent silencing. The researchers are currently trying to see the initiation and the aftermath of the gene silencing process after the first generation of transgenic plants. “That’s a huge challenge,” Slotkin points out. “We plant thousands of seeds that may have integrated a transgene. Sometimes we only get five plants back because they did not transform well. This isn’t enough, as we want a lot of tissue off of them in order to measure DNA methylation… and these experiments require biological replicates, so more tissue is needed, and the experiment needs to be done again.” Although it requires a tedious amount of work to grow and regrow enough plants for the experiment, “it is all worth it to be able to investigate the first generation of transgene silencing,” stated Slotkin.
The mechanism of DNA methylation directly relates to that of foreign gene silencing, which occurs in plants during genetic modification and complicates the production process. Their work shows potential benefits that could be brought by reducing the cost and effort required for successful transgenic crop production. “Gene silencing is a key bottleneck that is inhibiting plant improvement… no matter what new trait a plant biologist works on, they are going to have to fight against the tidal wave of gene silencing,” remarked Slotkin. While breeders normally require thousands of plants to analyze the few plants that successfully express instead of repressing the trait of interest, if how and why DNA methylation takes place is studied well and the most efficient way to prevent gene suppression is found, they can save money, time and money by achieving the transgenic procedure with silencing avoided from the outset. “One day we could start with three plants instead of thousands. All of the time and money that is usually put into producing a crop is slimmed down,” added Slotkin.
The research team of Slotkin is continuously working on the initiation of gene silencing. They are investigating the reason behind DNA methylation and the potential benefits of reducing drawbacks and hindrances in transgenic plant production. With increasing population, limited food resources, global warming and climate change, his work possesses a lot of potential benefits.
Edited By: Park, Jihye and Park, Changmo
Reference Donald Danforth Plant Science Center. (2021, November 9). Research finds key advances towards reducing the cost of plant improvement. ScienceDaily. Retrieved November 12, 2021, from www.sciencedaily.com/releases/2021/11/211109155215.htm