Sugarcane is one of the most important plants on Earth — at least for us humans. Not only does it provide 80% of the sugar and 30% of the bioethanol consumed worldwide, but the oil in its leaves and stems is also used to make bioplastics.
But there are two big problems with sugarcane. The first is its environmental impact. It takes huge amounts of water to grow and refine sugar (around nine gallons for a single teaspoon), and the whole process produces a lot of waste. To make matters even worse, sugar takes up large portions of agricultural land, fueling deforestation in several parts of the world.
For researchers, this environmental impact is also an opportunity — an opportunity to change the plant and make it more sustainable. But there’s another, different problem with sugar: it has a complex and messy genome, which makes it very difficult to change and edit it. It often takes over a decade for a single sugarcane cultivar to be properly developed, and crossbreeding sugarcane is notoriously difficult.
But new genetic tools can finally enable researchers to edit sugarcane in desired ways, says Fredy Altpeter, Professor of Agronomy at the University of Florida’s Institute of Food and Agricultural Sciences
“Now we have very effective tools to modify sugarcane into a crop with higher productivity or improved sustainability,” Altpeter said. “It’s important since sugarcane is the ideal crop to fuel the emerging bioeconomy.”
Altpeter and Postdoctoral Research Associate Ayman Eid used the so-called “genetic scissors” CRISPR. CRISPR is a family of DNA sequences found in the genomes of some bacteria and archaea and can be used to edit parts of the genome of both plants and animals, eliminating some sequences and replacing them with more desirable ones. This approach can be used to treat diseases in humans or animals, but also for improving crops.
In two studies, the two researchers and their colleagues did just that: edited the gene of sugarcane using the CRISPR. In the first study, they changed a few genes to change the appearance of the plant. This was more of a proof of concept, to know if it worked or not. They also turned off several copies of a gene that helps sugarcane produce chlorophyll, making the plants turn light green or even yellow. The light green ones seemed to require less fertilizers to grow while producing the same biomass and no detectable side effects, the researchers note.
In the second study, researchers replaced individual nucleotides (the individual building blocks of both RNA and DNA) with better versions that they hoped would give sugarcane more resistance to herbicides. Essentially, this meant editing the plant’s own DNA repair process and making it more resilient to herbicides.
The fact that both attempts worked offers great hope for breeding useful new varieties of sugarcane that can help reduce its dreadful environmental impact.
With conventional breeding, two different types of sugarcane would have been cross-bred to reshuffle the genetic information, hoping that the desirable trait (such as needing less fertilizer) is enhanced. The problem is that it’s not always possible to fully control this, and genes are transferred from parents to offspring in blocks, which means that the desired gene is linked to other, superfluous genes. Researchers often have to do multiple rounds of breeding, and screen the plant to see exactly what changed in the offspring. Genetic tools offer a much more elegant, cheaper, and quicker way to accomplish the same thing.
Of course, whether or not consumers will accept CRISPR-edited plants on the plates remains to be seen. Consumers are almost always wary of modifying the genes of plants, even when the scientific process has been shown to be safe.
Journal Reference: Ayman Eid et al, Multiallelic, Targeted Mutagenesis of Magnesium Chelatase With CRISPR/Cas9 Provides a Rapidly Scorable Phenotype in Highly Polyploid Sugarcane, Frontiers in Genome Editing (2021). DOI: 10.3389/fgeed.2021.654996
Mehmet Tufan Oz et al, CRISPR/Cas9-Mediated Multi-Allelic Gene Targeting in Sugarcane Confers Herbicide Tolerance, Frontiers in Genome Editing (2021). DOI: 10.3389/fgeed.2021.673566