Tiny plants reveal big potential for boosting crop efficiency

"Hornworts possess a remarkable ability that is unique among land plants: they have a natural turbocharger for photosynthesis," said Tanner Robison, a graduate student at the Boyce Thompson Institute (BTI) and first author of the paper recently published in Nature Plants. "This special feature, called a CO₂-concentrating mechanism, helps them photosynthesize more efficiently than most other plants, including our vital food crops."

At the heart of this mechanism is a structure called a pyrenoid, which acts as a microscopic CO₂ concentration chamber inside the plant's cells. The pyrenoid is a liquid-like compartment packed with the enzyme Rubisco, which captures CO₂ and converts it into sugar during photosynthesis. Surrounding the pyrenoid are specialized channels and enzymes that pump in CO₂, saturating Rubisco with its key raw material.

"This CO₂-concentrating mechanism gives hornworts a significant advantage," said Laura Gunn, assistant professor at Cornell's School of Integrative Plant Science. "Rubisco is an infamously inefficient enzyme, so most plants waste a lot of energy dealing with its tendency to also react with oxygen. But by concentrating CO₂ around Rubisco, hornworts can maximize its efficiency and minimize this wasteful 'photorespiration' process."

Using advanced imaging techniques and genetic analysis, the research team found that hornworts likely use a much simpler system to concentrate CO₂. Unlike algae, which need complex machinery to pump CO₂ into their cells, hornworts probably use a passive approach that requires fewer moving parts.

"It's like finding a simpler, more efficient engine design," explained Fay-Wei Li, associate professor at BTI and co-corresponding author of the study. "This simplicity could make it easier to engineer similar systems in other plants, like essential crops."

The potential impact is substantial. The research team estimates that installing a similar CO₂-concentrating mechanism in crops could boost photosynthesis by up to 60%, leading to significant increases in yields without requiring more land or resources.

The research also provides new insights into plant evolution. The scientists found that the machinery for concentrating CO₂ was likely present in the common ancestor of all land plants, but only hornworts retained and refined the ability over millions of years of evolution.

As we face the dual challenges of climate change and food security, this tiny plant might provide a blueprint for meaningful agricultural innovation. While much work remains before this natural technology can be utilized in other plants, the discovery offers a promising new direction for sustainable agriculture.

This research was supported by the National Science Foundation and the Triad Foundation.