Proteins in algae increase crop yields

Proteins discovered in algae could be used to engineer faster-growing crops, according to researchers at the Universities of York and Princeton.

When it comes to photosynthesis, the process of converting carbon dioxide (CO₂) to sugar using energy from sunlight, most algae are far more efficient at this task than land plants.

This is due to their use of a carbon-concentrating mechanism within a unique organelle called the pyrenoid. The main CO₂ fixing enzyme, Rubisco, clusters inside this organelle where it encounters high concentrations of CO₂ which is pumped in from the air.

Luke Mackinder, researcher at the University of York, was particularly interested in finding out more about the pyrenoid and its structure, ‘We knew very little about this organelle … we knew that it was fundamentally important for photosynthesis and hypothesised that we may be able to engineer this into plants to boost crop yields. However, we first needed to get an idea of its components’.

In the first of two studies published in Cell, Mackinder and his colleagues conducted a sweeping search for proteins involved in the carbon-concentrating mechanism of a species of algae called Chlamydomonas reinhardtii. The team developed protein labelling techniques that allowed the identification of 89 new proteins, including ones involved in the transport of carbon into the pyrenoid.

In a second study, the researchers found that the pyrenoid, once thought to be a solid structure, is actually liquid-like. In order to test the dynamics of this organelle, they tagged Rubisco enzymes using a fluorescent protein and then ‘turned off’ these tags in one half of the pyrenoid. Within 30 seconds, the fluorescently tagged Rubisco enzymes had distributed throughout the entire pyrenoid structure, demonstrating that they easily move around this organelle as they would in a liquid.

Mackinder believes that this liquid-like structure, and its ability to condense and disperse within the cell, may improve the efficiency of photosynthesis by allowing algae to adapt to rapidly changing CO₂ levels in their environment.

The team are now working with collaborators to engineer the proteins discovered in the pyrenoid into crop plants such wheat and rice. The aim is to improve the photosynthetic efficiency of these plants by introducing a carbon-concentrating mechanism and ultimately increase crop yield.

"In the future, I think we will have to make a choice about using biotechnology in food production.  The choice is to either try to increase yield using this kind of biotechnology and alleviate some of the food production issues we will face or choose not to use it and face the consequences of low production," says Mackinder.