Rice farmers in Africa suffer from the yellow spot virus, which destroys between 10% and 100% of the rice crop (African Crop Improvement Center)
Since the announcement of the development of genome editing technology (CRISPR/Cas9) in 2010, this technology, which is gaining new ground day after day, has seemed like a magic wand capable of providing solutions to intractable agricultural problems. The most recent solutions it provided were related to providing results indicating that it might The solution to rid rice farmers in Africa of the yellow spot virus problem.
The yellow spot virus is transmitted by beetles through direct contact with leaves, and poses a major threat to rice cultivation in Africa, as it causes yellow spots to appear on the leaves, leading to a decrease in chlorophyll and affecting the photosynthesis process.
Severe infection results in stunted plant growth, reduced yield, and in some cases plant death.
In Africa, where most farmers have small plots of land, between 10% and 100% of the rice crop is regularly lost to this virus, a problem that threatens the productivity of the poorest farmers.
The only effective protection against the virus is the development of rice varieties that carry a resistance gene, but introducing the gene directly is difficult due to “sterility in hybrids” problems between species.
Here comes the role that genome editing technology (CRISPR/Cas9) can play.
A picture showing the difference between normal rice plants and those that have been given the resistance gene (the research team)
Infertility in hybrids...what does it mean?
"Hybrid infertility" refers to the inability to produce viable offspring. In the context of interspecific hybrids, the mating of individuals from different species often leads to fertility problems in the hybrid offspring. This can be caused by differences in the number or structure of chromosomes, or Genetic incompatibility, or disorders in reproductive processes.
Applied to the quest to produce rice resistant to the yellow spot virus, the Asian type of rice (Oryza indica) is commonly grown in Africa due to its high productivity, but it lacks the resistance genes to the yellow spot virus that have been found in some African wild rice species, such as “Oryza glabrima.” .
When trying to introduce a resistance gene from wild rice directly into cultivated rice, the resulting plants (interspecific hybrids) may face infertility problems, as genetic differences between the two species lead to problems during meiosis (cell division to form reproductive cells), and hybrid plants may produce gametes Which are sterile or have low fertility, making it difficult for them to reproduce.
To overcome infertility problems, comes the role of genome editing technology (CRISPR/Cas9), which can be done by transferring the required gene from “Oryza glabrima” to “Oryza indica” while preserving fertility.
Yellow spot affects photosynthesis, stops growth, and causes plant death in some cases (An Splash)
Genome editing technology... How did researchers use it?
The use of this technology depends on several steps, which were detailed in a study published by the journal “Plant Biotechnology Journal,” which included researchers from members of the Healthy Crops Initiative (an international initiative that includes researchers from different countries of the world). These steps are:
First: Identify the resistance gene:
Researchers have identified the natural resistance gene RMV2 from wild rice (Oryza glabrima), which provides resistance to yellow spot virus.
Second: Designing a genome editing strategy (CRISPR/Cas9):
Using CRISPR/Cas9, researchers designed a strategy to introduce the yellow spot virus resistance gene into the Japanese rice variety Oryza sativa japonica, to explore whether it could work in Asian indica varieties in Africa.
Third: Delivery of CRISPR/Cas9 components:
Introducing CRISPR/Cas9 components, including the Cas9 protein and a guide RNA specifically designed for the RMV2 resistance gene, into Oryza sativa japonica cells, can be accomplished in different ways.
Fourth: Targeted editing of the resistance gene:
CRISPR/Cas9 induces targeted modifications in the resistance gene, which may involve introducing specific mutations or modifications to mimic naturally occurring resistance.
Fifth: Verifying the success of gene editing:
Researchers confirmed the success of CRISPR/Cas9 editing by analyzing the plant's genomic DNA.
Using techniques such as DNA sequencing or other molecular biology methods, they verified the presence of the required modifications in the resistance gene.
Sixth: Generating genetically modified plants:
'Oryza sativa japonica' plants that underwent CRISPR/Cas9 editing and carried the modified resistance gene RMV2 successfully grew to maturity.
Seventh: Evaluation of virus resistance:
Modified Oryza sativa japonica plants were exposed to yellow spot virus to evaluate their resistance by controlled inoculation with the virus.
Eighth - Moving to Africa:
After the success of a limited experiment with the Japanese Oryza sativa japonica species, through which the researchers proved the success of their idea, they are now planning to explore whether their method can succeed in Indica varieties found in Africa, such as Kombucha in Kenya.
A change in one gene can affect other genes or change metabolic pathways, affecting plant health and growth (Shutterstock)
Legitimate concerns... reassuring messages
Despite its success, this technology still raises concerns, some of which were mentioned by researcher at the Egyptian Agricultural Research Center Khaled Bahi, including that it may lead to “untargeted effects.”
Bahi says in a telephone interview with Al Jazeera Net: “Unintended genetic modifications can occur in sites other than the targeted site, which leads to undesirable consequences, affecting the natural function of the plant or leading to the introduction of unexpected traits.”
Bahi attributes this to the fact that “plant physiology is complex,” meaning that even subtle modifications can have unintended consequences, as changes in one gene can affect the expression of other genes or alter metabolic pathways, which can affect plant health and growth. in general".
He adds that the use of this technology in agriculture also raises ethical questions, including those related to ownership of genetic resources that contain the desired genes, and concerns about corporate control over agricultural practices.
For its part, Al Jazeera Net presented these legitimate concerns to two senior researchers participating in the study, namely Professor Wolf Frommer from the Institute of Molecular Physiology at the Heinrich Heine University of Düsseldorf, Germany, and Laurence Albar from the Institute of Plant Health in Montpellier, France, and we received reassuring responses. It confirms their awareness of these fears and their keenness to dispel them.
Frommer says: “We conducted a limited experiment on the Japanese rice variety (Oryza sativa japonica), and after we proved the success of the idea, we plan to expand to transfer the disease resistance gene to the Asian rice varieties that are commonly grown in Africa, and we will start with the kombucha variety in Kenya, and this means that our steps are not In a hurry.”
He denied fears of off-target effects, and said, "We used the basic approach of CRISPR/Cas9 technology, which leads to small, undirected mutations at a specific location in the genome. We are now able to do this more accurately, and we did not detect any other defects in the producing plant."
He added, "Mutations occur naturally all the time, so at present I do not see any ethical or environmental concerns, especially since we are completely non-profit scientists, and have no commercial interests."
Albar confirms what his colleague Frommer said, and says: “The mutations introduced by genome editing in our experiment are very similar to mutations found naturally in some wild African Oryza glabrima varieties, and therefore such mutations do not represent a problem in and of themselves.”
He adds: “However, the use of varieties developed by CRISPR/Cas9 technology is still subject to regulation in some countries, but an increasing number of countries now consider that this technology does not raise ethical or environmental issues, and have allowed plants obtained in this way. For example, genome-edited plants are permitted in Kenya and Nigeria.”
He explains that the next step for them is to use this technology to transfer resistance into a rice variety that African farmers already use and appreciate. In addition, field trials will be conducted in relevant agro-ecosystems before the technology is deployed to ensure that the mutation introduced is not associated with negative side effects. "It targets locally present strains of the virus."
Source: Al Jazeera