TAG: GS 3: SCIENCE AND TECHNOLOGY
THE CONTEXT: A groundbreaking research effort led by a team at the Innovative Genomics Institute at the University of California, Berkeley (UCB), has utilized CRISPR/Cas9 gene-editing technology to enhance gene expression in a food crop.
EXPLANATION:
- This achievement represents a significant milestone as it is the first unbiased approach using CRISPR/Cas9 to increase gene expression and subsequent photosynthetic activity.
- Published in Science Advances, this study deviates from traditional CRISPR applications that primarily focus on gene knockouts or reducing gene expression.
Key Contributions and Innovations
- The study’s lead author and a former postdoctoral researcher in the Niyogi Lab at UCB emphasized the novel approach of using CRISPR/Cas9 to fine-tune gene expression rather than merely turning genes off.
- Previous research primarily utilized CRISPR to diminish gene activity, particularly genes involved in trade-offs like plant architecture and fruit size.
- The research was inspired by a 2018 Nature Communications paper that successfully increased water-use efficiency in crops by overexpressing the PsbS gene, which is involved in photoprotection.
- The Niyogi lab aimed to enhance the expression of native plant genes without incorporating foreign DNA, thus avoiding the complexities associated with synthetic biology strategies that use external genes.
Choice of Model System
- Rice, a staple food crop that provides 20% of the world’s calories.
- It was chosen as the model system due to its possession of only one copy of each of the three key photoprotection genes.
- This made it an ideal candidate for the study, which was part of the Realizing Increased Photosynthetic Efficiency (RIPE) project.
- RIPE, an international collaboration led by the University of Illinois and supported by the Bill & Melinda Gates Foundation, Foundation for Food & Agriculture Research, and the U.K. Foreign, Commonwealth & Development Office, seeks to boost global food production by improving photosynthetic efficiency.
Technique and Results
- The researchers employed CRISPR/Cas9 to modify the upstream regulatory DNA of the target gene, controlling its expression levels.
- Their hypothesis was that alterations in this regulatory region would significantly impact downstream gene activity.
- Remarkably, the changes in DNA resulted in a more substantial increase in gene expression than anticipated, showcasing the inherent plasticity of plant genomes.
- Plants have adapted to extensive genetic changes over millions of years, which researchers can now leverage for rapid improvements in crop efficiency and climate adaptability.
Findings of the study
- The study revealed that inversions or “flipping” of the regulatory DNA led to increased expression of the PsbS gene.
- Following the largest inversion, RNA sequencing was conducted to assess the overall gene activity in the modified rice plants.
- The results indicated a minimal number of differentially expressed genes compared to similar transcriptome studies, suggesting that their gene-editing approach did not disrupt other essential processes in the plants.
Challenges and Future Implications
- While the study demonstrated the potential of this gene-editing method, the success rate was relatively low, with only about 1% of the plants exhibiting the desired phenotype.
- Patel-Tupper highlighted that although this proof-of-concept study shows the feasibility of using CRISPR/Cas9 to generate significant genetic variations in crops, it remains a challenging task compared to traditional plant breeding methods.
- Despite the difficulty, this approach has the advantage of potentially circumventing regulatory hurdles associated with transgenic plants.
- By altering existing genetic material rather than introducing foreign genes, this method may expedite the development and deployment of improved crop varieties to farmers.
CRISPR/Cas9
- CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding or altering sections of the DNA sequence.
- It is currently the simplest, most versatile and precise method of genetic manipulation and is therefore causing a buzz in the science world.
- The CRISPR-Cas9 system consists of two key molecules that introduce a change (mutation) into the DNA. These are:
- an enzyme called Cas9. This acts as a pair of ‘molecular scissors’ that can cut the two strands of DNA at a specific location in the genome so that bits of DNA can then be added or removed.
- a piece of RNA called guide RNA (gRNA). This consists of a small piece of pre-designed RNA sequence (about 20 bases long) located within a longer RNA scaffold. The scaffold part binds to DNA and the pre-designed sequence ‘guides’ Cas9 to the right part of the genome. This makes sure that the Cas9 enzyme cuts at the right point in the genome.
- The guide RNA is designed to find and bind to a specific sequence in the DNA. The guide RNA has RNA bases that are complementary to those of the target DNA sequence in the genome. This means that, at least in theory, the guide RNA will only bind to the target sequence and no other regions of the genome.
SOURCE: https://phys.org/news/2024-06-team-crisprcas9-photosynthesis.html
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