Hornworts: Tiny Plants Could ‘Turbocharge’ Crop Yields, Study Finds

The seemingly simple hornwort, a small land plant, is offering researchers a surprising pathway to potentially “turbocharge crop yields,” according to a recent report from the Boyce Thompson Institute (BTI). This discovery centers around how plants manage the notoriously inefficient enzyme Rubisco, crucial for photosynthesis – the process by which plants convert sunlight into food. The findings, published in the journal Science, suggest that nature has already devised elegant solutions to improve carbon capture, and these can be adapted for use in major food crops like wheat and rice.

The Rubisco Bottleneck and Nature’s Workarounds

Rubisco, short for ribulose-1,5-bisphosphate carboxylase/oxygenase, is arguably the most important enzyme on the planet. It’s the first step in fixing atmospheric carbon dioxide into usable energy for plants. But, as BTI Associate Professor Fay-Wei Li explains, Rubisco isn’t particularly good at its job. “Rubisco is arguably the most important enzyme on the planet because it’s the entry point for nearly all carbon in the food we eat,” Li said in a Phys.org article. “But it’s slow and easily distracted by oxygen, which wastes energy and limits how efficiently plants can grow.” This inefficiency has long been a target for agricultural improvement.

Some organisms, particularly algae, have evolved a clever solution: they concentrate carbon dioxide around Rubisco within specialized compartments called pyrenoids. These microscopic “bubbles” increase the enzyme’s efficiency by minimizing its exposure to oxygen. Scientists have long sought to transfer this system to crops, but the complex machinery of algae has proven difficult to replicate in other plant species.

Hornworts: A More Accessible Model

The breakthrough came with a shift in focus to hornworts – a group of non-vascular land plants that, uniquely, also possess CO₂-concentrating compartments similar to those found in algae. Researchers hypothesized that because hornworts are more closely related to crops than algae, their molecular mechanisms might be more readily transferable. This proved to be correct, but the solution wasn’t what they initially expected.

Instead of relying on a separate “packing protein” to cluster Rubisco together, as seen in algae, hornworts have modified Rubisco itself. Researchers discovered a unique molecular “tail” – dubbed the STAR region – on one version of the enzyme’s small subunit. This tail acts like built-in velcro, causing Rubisco molecules to condense into a tight, CO₂-rich compartment. “Instead, we discovered they’ve modified Rubisco itself to do the job,” said researcher Tanner Robison, as reported by The Cool Down.

Replicating the Mechanism in Other Plants

The team successfully tested this modified Rubisco (RbcS-STAR) in a related species lacking pyrenoids, effectively replicating the carbon-concentrating effect. They then extended their experiments to less closely related plants, achieving similar success. This suggests the STAR region modification is a versatile mechanism that can be applied across a range of plant species.

This discovery is significant because it bypasses the challenges associated with transferring the entire pyrenoid structure from algae. Modifying Rubisco directly appears to be a more straightforward and potentially more effective approach to improving photosynthetic efficiency.

Genome Stability and Evolutionary Insights

The success of this research is also linked to recent advances in understanding the hornwort genome. A 2025 study from BTI, detailed in BTI News, revealed that hornworts have remarkably stable chromosomes despite evolving for over 300 million years. This stability, coupled with the presence of dynamic “accessory chromosomes” that allow for rapid adaptation, may explain their unique ability to evolve efficient carbon-concentrating mechanisms.

The study found that hornworts haven’t experienced whole-genome duplication, resulting in stable “autosomes” – the chromosomes containing most of the genetic material. However, they do possess “accessory chromosomes” that are more flexible and can contribute to beneficial traits.

Implications for Agriculture and Food Security

The potential implications for agriculture are substantial. Improving Rubisco efficiency could lead to significant increases in crop yields, potentially addressing growing concerns about global food security. By mimicking the natural solutions found in hornworts, researchers hope to engineer crops that require less water, fertilizer, and land to produce the same amount of food.

As Li emphasizes, this research highlights the value of studying nature’s existing solutions. “This research shows that nature has already tested solutions we can learn from. Our job is to understand those solutions well enough to apply them where they’re needed most — in the crops that feed the world.”

Next Steps: From Lab to Field

The next phase of research will focus on optimizing the RbcS-STAR modification for specific crops and conducting field trials to assess its performance under real-world conditions. This process will involve rigorous testing to ensure that the modified Rubisco doesn’t have any unintended consequences for plant growth or development. Further research will also explore the potential for combining the STAR region modification with other strategies for improving photosynthesis, such as optimizing light capture and water use efficiency. The team will also need to address potential regulatory hurdles and public acceptance issues before genetically modified crops with enhanced Rubisco efficiency can be widely adopted.