Most of us feel an unpleasant twitch when we talk about genetically modifying the plants we eat. We think about changing complex mechanisms that can have far-reaching, unknown effects. But what if it was something much simpler? In a new study, researchers used the genetic scissors CRISPR/Cas9 system to tweak the leaf angle in sugarcane, enabling the plant to capture more sunlight. This single change had a big effect on the amount of biomass produced.

Sugar fuel

Sugarcane is one of the most important crops in the world. In fact, by biomass yield, it’s the world’s largest crop, with almost 2 billion tons being produced every year. It produces 80% of the sugar the entire world uses. But there’s another reason why scientists are interested in it: biofuel.

Because the sugarcane plant is pretty big and uses water very efficiently, it’s a prime candidate to produce various bioproducts. But, notably, it is useful in producing biofuel. Currently, Sugarcane is used to produce almost 40% of global biofuels. Supporters of the technology say it could even potentially replace jet fuel.

There’s another advantage to using sugarcane for biofuel instead of food: our biases. People are usually very resistant to eating genetically modified foods. But they are less interested in where their fuel comes from (as we’ve unfortunately all seen during the ongoing climate crisis).

Genes and leaves

Editing sugarcane, however, is not an easy feat. Most cultivars used are hybrids of two plants (Saccharum officinarum and Saccharum spontaneum), resulting in a chromosome number ranging from 100 to 120. This genetic intricacy necessitates innovative approaches for crop improvement.

Sugarcane’s genetic makeup is all the more complex because it contains numerous copies of each gene. This redundancy means that the traits a sugarcane plant exhibits result from the combined effects of these multiple gene copies. But the CRISPR/Cas9 gene-editing tool (often called “genetic scissors”) is ideally suited for this task. It can be tailored to modify either a small number or a large number of these gene copies simultaneously.

Researchers from the University of Florida used CRISPR/Cas9 to focus on the LIGULELESS1 (LG1) gene, which plays a crucial role in the development of leaf ligules and auricles in grasses.

They wanted to manipulate this gene to optimize the canopy architecture of sugarcane. By using the CRISPR/Cas9 system, they targeted multiple copies of the LG1 gene within the sugarcane genome, inducing mutations that resulted in varying leaf inclination angles. These modifications allowed the researchers to identify the optimal leaf angle for maximizing light capture and biomass yield.

“In some of the LG1 edited sugarcanes, we just mutated a few of the copies,” said Fredy Altpeter, research team lead and Professor of Agronomy at the University of Florida. “And in doing so, we were able to tailor the leaf architecture until we found the optimal angle that resulted in increased biomass yield.”

Building biomass

Three transgenic lines with varying levels of LG1 co-editing (12%, 53%, and 95%) were cultivated under greenhouse and field conditions. These trials revealed that as the co-editing frequency increased, the leaf inclination angle became more upright. The most notable results were observed in the line with 12% co-editing, which caused a 56% decrease in the leaf inclination angle and an 18% increase in dry biomass yield.

The implications of this research are profound and can mark a significant milestone in editing crops. It shows how a genetic tool can optimize leaf architecture, opening up an exciting new avenue for enhancing biomass yield, a critical factor for many different crop plants.

“This is the first peer-reviewed publication describing a field trial of CRISPR-edited sugarcane,” Altpeter said. “And this work also shows unique opportunities for the editing of polyploid crop genomes, where researchers can fine-tune a specific trait.”

Journal Reference: Eleanor J. Brant et al, The extent of multiallelic, co‐editing of LIGULELESS1 in highly polyploid sugarcane tunes leaf inclination angle and enables selection of the ideotype for biomass yield, Plant Biotechnology Journal (2024). DOI: 10.1111/pbi.14380