How The Humble Hornwort Could Supercharge Agriculture

(Adobe Stock via Minnesota News Connection)

(By Matt Simon for Grist.) – You are here because of a single, all-important enzyme. But don’t look inward to find ribulose-­1,5-­bisphosphate carboxylase/oxygenase, known more mercifully among scientists as rubisco. Instead, look to the food you eat and the trees that manufacture oxygen, as this is the protein that makes photosynthesis possible. Without it, life on Earth as we know it would not exist.

For all that heavy lifting, rubisco is remarkably inefficient. The enzyme converts carbon dioxide into sugars that sustain plants. But it is easily confused, and will react with oxygen in a process that creates a toxic byproduct, wastes energy, and limits how quickly plants can grow. (Which is not to fault rubisco: This is a very difficult reaction to pull off, and just look at how many plants have been getting it right for hundreds of millions of years.) That includes the essential crops that feed humanity — grains, vegetables, fruits — that could theoretically grow better if their rubisco worked more efficiently. This problem becomes more urgent as global temperatures rise, because this essential protein gets even less efficient in the heat.

Enter the hornwort. This tiny plant, which is related to mosses, grows as a green sheet on the ground. It’s the only known land plant that’s found a way (evolutionarily speaking) to supercharge rubisco by concentrating CO2 around the enzyme.

Now, an international team of scientists says it has figured out how hornwort does this, and how it may be able to apply that superpower to crops. That could mean massively improved yields, so farmers wouldn’t need to cultivate as much land to grow the same amount of food. “It’s very impressive,” said Robert Wilson, a biochemist who studies rubisco at the Massachusetts Institute of Technology. (Wilson wasn’t involved in the research but does collaborate with one of the scientists.) “It’s interesting, because it’s a completely new and novel mechanism through which an important aspect of rubisco biochemistry occurs.”