Of all the enzymes on Earth, Rubisco may be the most important and the most frustratingly inefficient.
Rubisco is responsible for the central act of plant life: capturing carbon dioxide from the air and fixing it into sugar — the process that ultimately feeds almost every living thing. It is the most abundant enzyme on the planet, with hundreds of millions of tonnes of it packed into plants, algae, and bacteria across the biosphere.
It is also, by biochemical standards, remarkably slow and somewhat clumsy. Rubisco makes mistakes. It sometimes grabs oxygen instead of CO₂ — a wasteful process called photorespiration that costs plants significant amounts of the energy they've worked to collect. Scientists have spent decades trying to engineer it to work better, because even a modest improvement in Rubisco efficiency would translate into meaningfully higher yields for the crops that feed the world.
The answer, it turns out, may have been sitting in the soil all along — in a tiny, unremarkable plant that most people have walked past without noticing.
**The Hornwort Secret**
Hornworts are ancient plants — a small group of non-vascular land plants that look something like flat, waxy liverworts and grow quietly in moist, shaded environments. They are not glamorous. They are not crop plants. They are rarely studied.
But they have a trick that sets them apart from almost every other land plant on Earth.
A research team led by scientists at the **Boyce Thompson Institute (BTI)** at Cornell University, working with colleagues at the **University of Edinburgh**, discovered that hornworts possess a unique protein component called **RbcS-STAR**. This protein acts like molecular velcro — it causes Rubisco molecules to cluster together into dense compartments called **pyrenoids**, similar to structures found in algae that are known for their photosynthetic efficiency.
The clustering isn't just structural. By drawing Rubisco into concentrated compartments, it allows the enzyme to work in a high-CO₂ micro-environment — flooding the enzyme with the molecule it needs, and suppressing the chance of oxygen grabbing a spot instead. The result: Rubisco makes fewer mistakes and fixes more carbon, more efficiently.
Published in March 2026, the study was reported by ScienceDaily on March 11, 2026.
**The Breakthrough: It Transfers**
The truly exciting part of the discovery isn't that hornworts have this trick — it's that when the researchers introduced the RbcS-STAR component into *Arabidopsis*, a common laboratory plant used as a model for crop research, **it worked**. The Rubisco molecules in Arabidopsis reorganised into similar clustered structures.
This is significant for a specific reason. The complex carbon-concentrating mechanisms in algae have long been known, but they involve many interacting components, making them difficult to engineer into higher plants. Hornworts represent a simpler, closer evolutionary step — a land plant that has developed a more elegant version of the same trick.
The closer evolutionary relationship between hornworts and crop plants means the machinery is more compatible. It can be transferred with fewer complications.
**The Prize: Wheat and Rice**
The researchers are clear about what they're ultimately aiming for: improving photosynthetic efficiency in the staple crops that feed billions of people — particularly **wheat** and **rice**.
Current estimates suggest that even a 20% improvement in photosynthesis efficiency could translate into meaningful yield increases across global agriculture. Given that the world needs to feed an additional 2–3 billion people by mid-century, on roughly the same amount of arable land, while dealing with more frequent droughts and heat events — any tool that improves yield per hectare is critically important.
*"The closer evolutionary relationship of hornworts to crops makes this a more feasible path to engineering photosynthesis improvements than the algae approach."* — Boyce Thompson Institute, March 2026
**The Work Ahead**
The researchers are careful to note that transferring the mechanism to Arabidopsis in the lab is an early step. Optimising the delivery of carbon dioxide to the newly clustered Rubisco — and demonstrating improved yield in actual crop plants under field conditions — remains ahead.
But the discovery of RbcS-STAR provides a clear molecular target. Scientists now know *what* to transfer, and have early evidence it *can* be transferred. That's a significant narrowing of the problem.
Hundreds of millions of years of plant evolution produced hornwort's quiet efficiency. The hope is that human ingenuity can borrow it, scale it, and bring it to the fields that feed the world. 🌿
*Sources: ScienceDaily (March 11, 2026) · Boyce Thompson Institute · Cornell University · University of Edinburgh · The Cooldown · National Today*
