CRISPR: Gene-Editing is Making Plants Better

 

Note: The National Horticulture Foundation (NHF) continues to seek out industry partnerships to support research providing a greater return on investment for the green industry.  With more than $500,000 in research support already awarded for projects in production, marketing, utilization and distribution, NHF’s mission is never complete. Revolutionary technology such as CRISPR: Gene-Editing technology could not be used to its full potential without continued interaction with the green industry and its financial support. 

With compliments of the UF’s Mid Florida Research and Education Center, NHF would like to share more information about this exciting new technology and provide a strong reason why your support is so critical.  NHF is steadfast in supporting the science that backs up the facts, and invites you to join our efforts.

By Heqiang Huo and Caroline R. Warwick

When Microsoft first released “Word”, it was a revolutionary technology. Suddenly the ability to freely edit text – inserting, deleting, revising and replacing words – was at your fingertips. A new revolutionary technology, called CRISPR, short for Clustered Regularly Interspaced Short Palindromic Repeats, has given scientists the ability to do the same – but with the plant genome. What exactly is CRISPR? CRISPR is a tool scientist can use to precisely cut and modify genomic DNA of many organisms. This means scientists can use different versions of CRISPR enzymes to do different types of gene editing, such as deletion of a gene to promote flowering, editing a gene to improve disease resistance of elite cultivar, or converting a single nucleotide from cytosine to thymine to make a herbicide resistant crop. Theoretically, scientists can use this powerful tool to reshuffle any gene in almost any organisms in very near future.

Just as CRISPR can knock out a gene in a plant to improve a trait, it also knocks out our concerns surrounding the safety and virtue of genetically modified organisms (GMO). Before the advent of CRISPR, plant scientists were trying to avoid creating GM plant varieties since these plants would have been subjected to strict and costly regulatory screening by both the USDA and FDA to prove their safety to human beings and environments. Why do people have a big concern on GM plants? Well, genetically modified crops generally contain foreign genes that do not come from plant species. For example, neomycin phosphotransferase II (NPTII) is generally used in selection of transformed plants. This gene was initially isolated from bacterium Escherichia coli K12, which can provide plant resistance to a range of aminoglycoside antibiotics such as kanamycin. Similarly, a bar gene from Streptomyces soil bacteria is also extensively used as selection markers, which can provide plants with herbicide resistance.  These foreign DNA fragment will stay inside plant genome together with the gene of interest that is responsible for improved desirable traits. After years of debating, publics are still skeptical of whether these foreign DNA will have deleterious effect on human health or whether herbicide resistance can be transferred into weeds for creating “Super Weeds”.

Unlike the traditional genetic modification tools, CRISPR allows researchers to edit existing DNA – similar to editing a Word document. CRISPR can be used like a keyboard, giving researchers the power to cut, paste and revise part of a plant’s genetic codes. CRISPR technology is quicker than traditional breeding techniques since it gives researchers the ability to precisely and quickly remove or add a specific plant trait. One of the complications with traditional breeding methods revolves round the thousands of years that humans have already selectively bred plants. Often, researchers struggle to “fix” problems since they cannot precisely target what needs to be changed. CRISPR technology changes all of that. Rather than spending years of working on crossbreeding plants to achieve the exact goal, researchers can simply analyze plant genomes and edit specific genes as easy as you can edit a Word document.

CRISPR methods allow researchers to utilize a guided, small RNA to precisely target a specific gene for editing - similar to you making changes to a sentence in a paragraph - which simply adds value without generating adverse effects on other traits. Plant breeding with CRISPR technology will be precise, affordable, and fast. However, challenges still exist for plant scientists hoping to utilize CRISPR in plant species genetic improvement. One of the biggest challenges is the delivery of this tool into plant’s genome. Unfortunately, current CRISPR introduction systems are only established for particular genotype of a limited number of plant species. Another challenge is how to remove CRISPR DNA fragments after they complete the editing process. CRISPR DNA fragments can be easily discarded through seed segregation for annual plants to create pure non-GMO plants without foreign DNAs. However, this is especially difficult when working with foliage or perennial plants that do not bear true seeds like orange. Lastly, understanding of a species’ genome, including the identity of genes that code for desired traits, as well as combating physiological conditions like seed production, are the other main hurdles to widespread use of gene editing. As DNA sequencing technology continues to advance rapidly, more genomic sequences will be available for a range of plant species. CRISPR can then be extensively used for plant breeding when more efficient delivery methods are developed.

This powerful and transformative technology attracts eyes from everyone ranging from academic research scientists to giant agricultural and pharmaceutical companies. Even Bill Gates understands the potential impact of this technology saying, “Gene editing to make crops more abundant and resilient could be a lifesaver on a massive scale.” Gene edited crops including corns, wheats, tomatoes, soybeans, mushrooms and rice have been developed and will be commercialized soon. The USDA recently announced that gene edited plants will not require any additional regulations or labeling since they are as safe as those produced through conventional breeding approaches. Overall, using CRISPR technology is a revolutionary way to breed plants, and, much like Word was to writing, will change the path and capabilities of plant scientists around the country.

Heqiang (Alfred) Huo is an assistant professor and plant breeder at the UF/IFAS Mid-Florida Research and Education Center. He is currently using advanced biotechnology tools including CRISPR technology to improve drought and heat tolerance, herbicide resistance in annual horticultural crops.

Caroline R. Warwick is an agricultural communicator at the UF/IFAS Mid-Florida Research and Education Center. She is a professional writer in research and extension of horticultural plant science.