A Breakthrough In Biotechnology And The Future Of The Fruit Industry

Kenong Xu (Photo credit: Robyn Wishna/Cornell University)

Kenong Xu (Photo credit: Robyn Wishna/Cornell University)

Researchers from California and Sweden have recently been honored for a discovery that could have big implications for the fruit industry. Dr. Jennifer Doudna, University of California, Berkeley, and Dr. Emmanuelle Charpentier, Helmholtz Center for Infection Research and Umeå University in Sweden, have been awarded with the 2015 Breakthrough Prize for their successful development of a new biotechnology, called CRISPR/Cas9. The Breakthrough Prize Foundation, which was established in 2012, recognizes distinguished scientists by granting each a $3 million award for their outstanding contributions to fundamental physics, life sciences, and mathematics.

Basics Of The Technology
CRISPR stands for clustered regularly interspersed short palindromic repeats, and Cas stands for CRISPR associated-nuclease. In simple terms, CRISPR and Cas9 are two molecular components identified in an innate bacteria defense system that can cut and destroy the DNA of a virus invading their cells.


By reprograming CRISPR and Cas9 into a modular-like system, Doudna and Charpentier brilliantly transformed the bacteria defense system into a versatile plug-and-play tool for genetic engineering. In practice, scientists can use CRISPR/Cas9 like a cut-and-paste editing tool to precisely modify, add, remove, or replace genomic DNA in living cells. What is needed is simply to plug the target gene information into the system for the desired changes.

For this reason, CRISPR/Cas9 is regarded the most advanced tool for precision genome editing, a process in genetic engineering where desirable changes are made precisely in their native environment in the genome. It has been shown, in theory, that CRISPR/Cas9 can target almost all genes in the genome of any given organism.

Since the breakthrough research work on CRISPR/Cas9 was published in the journal Science in 2012, scientists have proven that the technology is widely applicable in cells of a range of living organisms, including humans, animals, and plants. In humans, this technology has been tested for gene therapy to cure important deceases such as AIDS, sickle-cell anemia, and cancer.

How This Research Applies To Plant Improvement
Multiple plant species have been reported with success in using the CRISPR/Cas9 system, including arabidopsis, corn, sorghum, soybean, sweet orange, rice, tobacco, tomato, wheat, and others. Such rapid and wide-spread adaptation in plants indicates the technical robustness of the CRISPR/Cas9 system.

Figure 1. Targeted mutation of the rice LAZY1 gene using CRISPR/Cas9. Note the difference in tiller angle between the wild type (normal) and the mutant created by CRISPR/Cas9. Adapted from Miao et al. (2013)

Figure 1. Targeted mutation of the rice LAZY1 gene using CRISPR/Cas9. Note the difference in tiller angle between the wild type (normal) and the mutant created by CRISPR/Cas9. Adapted from Miao et al. (2013)

In a recent report, the potential impact of CRISPR/Cas9 on crop improvement has been clearly demonstrated. The study targeted a rice gene (Lazy1) that is required in order to grow tillers with normal (vertical) angle. By changing just a few DNA bases of the gene using CRISPR/Cas9, the rice plants were transformed from producing vertical tillers to growing wide-spreading tillers (Figure 1). Although this does not necessarily represent an improvement in rice, it shows how quickly and how dramatically a plant can be changed using the CRISPR/Cas9 system.

Successful reports of using CRISPR/Cas9 in tree fruits are not available currently. But efforts have been undertaken and several high-value target genes have been identified, such as the fruit acidity gene (Ma1) in apple, and the peach pillar growth habit gene (TAC1), which is closely related to the rice gene (Lazy1) mentioned above.

Compared with conventional genetic engineering, the CRISPR/Cas9 system has several unique features in crop improvement:
■ Genetic changes are made in specific genes at native locations of the genome.
■ Crop plants improved by CRISPR/Cas9 can be free of foreign DNA, making them comparable with those developed by conventionally mutation breeding methods, such as chemical treatment or physical irradiation, in terms of genetics.
■ If foreign genes must be introduced, they will be integrated into genomic locations that are carefully chosen and known of minimal or none negative effects on other genes.
■ Targeting multiple genes in a single experiment has been proven to be doable in several species, allowing manipulating traits involving multiple genes.

Government Regulation And Consumer Acceptance
The U.S. and Canadian governments regulate genetically engineered crops based on their potential for risk to environment and human health. In several cases, when a new crop variety developed by genetic engineering but containing no foreign DNA requested deregulation, USDA determined that these plants fell outside of the agency’s authority. This appears to suggest that genetic engineered new crop varieties without foreign DNA can be considered equivalent to cultivars bred conventionally.

Surveys of consumers’ attitude towards genetic engineered crops containing genes only from their relative species showed that they are significantly more acceptable than those carrying genes from non-related species.

Overall, biotech foods have been a part of our food supply system for nearly 20 years. Biotech apples have also been approved in the U.S. and Canada. These facts, together with the development of the CRISPR/Cas9 system — a tremendous breakthrough in biotechnology — hint at an important forward momentum, i.e. new and better biotech crops are coming. Food crops developed by genetic engineering will be continuously co-existing with those bred by conventional breeding in our food production system in the future.