Agricultural scientists specialized in breeding crops using gene editing have been using a tool called CRISPR cas9 to knock out a particular gene which is causing a challenge for the plant to break down

This can be a challenge of the plant succumbing to disease thereby getting destroyed and causing yield loss in farmer fields

In Uganda one particular scientists Dr John Odipio who underwent his PHD studies specializing in use of gene editing in plant breeding conducted research in cassava breeding using CRISPR cas9 to knock out the gene which causing  Cassava Brown Streak Virus in the plant.

The scientists are not only looking at using genome editing to develop varieties that can resist the disease but also fight off the white flies that spread the virus between plants.

The research work is ongoing and the researchers will share results one they have completed the research

Gene editing using CRISPR cas9 is technology that gives scientists the ability to change an organsim’s DNA.

These technologies allow genetic material to be added, removed or altered at particular locations in the genome.

However scientists are advancing the technology further using gene editing to increase gene expression and down =stream photosynthetic activity.

Gene editing to alter Photosynthesis is rice breeding

A team of scientists from Innovative Institute at the University of California, Bekeley have conducted research by producing an increase in gene expression in rice by changing its regulatory DNA

Their research results which registered success was published in Sciences Advance Science, a peer-reviewed multidisciplinary open-access scientific journal published by the American Association for the Advancement of Science.

Research process

Explaining the background the scientists noted that plants compete for light partly by over producing chlorophyll in leaves.

The resulting high light absorption is an effective strategy for outcompeting neighbouring farms in mixed communities.

The absorption of excess protons by upper leaves reduces the amount of sunlight within the canopy that is used for photosynthesis and negatively impact on crop yield 

The scientists used CHRISPR cas9mediated approach to engineer rice plants with condensed light harvesting antenna through knockout mutation to individual antenna assembly genes.

They compared the photosynthetic contribution of these components in rice by studying the growth rate of the whole plant, the energetic efficiency of photosynthesis process, chlorophyll density and distribution of photosynthesis abnormalities.

They also investigated duplication of the above process in plants such as rice, wheat, millet and sorghum.

The mutation in the relevant genes involved in the antenna assembly decreased chlorophyll content and light absorption and increased photosynthesis per proton (the positively charged particles present in nucleus of an atom) absorbed.

The above result have significant implication for improvement of high leaf index in crop growth process.

The studies suggested that mutations that reduce the size of the light harvesting antenna complexes, producing mutants referred to as truncated light antenna mutants may improve yield by increasing light penetration deeper into the plant canopy

The scientists then harvest light using the chloroplast light harvesting antenna for increase in chlorophyll uptake

This is regulated by reducing light harvesting pigment concentration to improve photosynthesis.

This led to mutation in rice to reduce the plant height and with no loss in grain mass.

The scientists went ahead to grow rice plants in green houses under 28 degrees Celsius in day temperature and 26 degrees Celsius in night temperature. The plants were grown in soilless media and watered daily.

Leaves were collected from four week old plants from the mutant lines and their DNA converted using synthesis kit.

The result of the research indicated that regulated photosynthesis process using gene editing technology can lead to equal spread of light thereby leading to rice plant leaves receiving equal light for photosynthesis to take place.

Publication summary

In the peer reviewed journal publication the scientists noted that "Tools like CRISPR/Cas9 are accelerating our ability to fine-tune gene expression in crops, rather than just knocking out genes or turning them 'off.' Past research has shown that this tool can be used to decrease expression of genes involved in important trade-offs, such as those between plant architecture and fruit size," said Dhruv Patel-Tupper, lead author on the study.

“This is the first study, to our knowledge, where we asked if we can use the same approach to increase the expression of a gene and improve downstream activity in an unbiased way,” he added.

The team noted that unlike synthetic biology strategies that use genes from other organisms to improve photosynthesis, the genes involved in the photoprotection process are naturally found in all plants.

According to the Food and Agriculture Organization, rice supplies at least 20% of the world's calories and because it has only one copy of each of the three key photoprotection genes in plants, it was an ideal model system for this gene editing study.

The scientists pursued this work as part of realizing increased Photosynthetic Efficiency, an international research project led by the University of Illinois that aims to increase global food production by developing https://phys.org/tags/food+crops/">food crops that turn the sun's energy into food more efficiently

The research was done with support from the Bill & Melinda Gates Foundation, Foundation for Food & Agriculture Research, and U.K. Foreign, Commonwealth & Development Office.

The laboratory plan was to use CRISPR/Cas9 to change the DNA upstream of the target gene, which controls how much of the gene is expressed and when.

They wondered if making those changes would have an impact on downstream activity and by how much. Even they were surprised at the results.

"The changes in the DNA that increased gene expression were much bigger than we expected and bigger than we've really seen reported in other similar stories," said Patel-Tupper Science and Technology Policy Fellow at the United Stated Department of Agriculture.

"We were a little bit surprised, but I think it goes to show how much plasticity plants and crops have. They're used to these big changes in their DNA from millions of years of evolution and thousands of years of domestication. As plant biologists, we can leverage that 'wiggle room' to make large changes in just a handful of years to help plants grow more efficiently or adapt to climate change."

In this study the researchers learned that inversions of the regulatory DNA, resulted in increased https://phys.org/tags/gene+expression/">gene expression.

Unique to this project, after the largest inversion was made to the DNA, the team members conducted an RNA sequencing experiment to compare how the activity of all genes in the rice genome changed with and without their modifications.

What they found was a very small number of differentially expressed genes, suggesting their approach did not compromise the activity of other essential processes.

Patel-Tupper added that while the team showed that this method is possible, it's still relatively rare. Around 1% of the plants they generated had the desired phenotype.

The team has showed a proof of concept, that they can use CRISPR/Cas9 to generate alternatives in key crop genes and get the same leaps as they would in traditional plant breeding approaches, but on a very focused trait that they want to engineer and at a much faster timescale.

It's definitely more difficult than using a transgenic plant approach, but by changing something that is already there within the plant the team may be able to pre-empt https://phys.org/tags/regulatory+issues/">regulatory issues that can slow how quickly they get tools like this into the hands of farmers.