Aussie-led research could bring the world turbocharged rice, wheat, and cotton - thanks to a photosynthesis quirk nature evolved millions of years ago.
Nicola McCaskill

11 Apr 2016 - 3:39 PM  UPDATED 11 Apr 2016 - 4:08 PM

If plants hadn’t evolved to convert sunlight into food via photosynthesis, there would be no humans.

“It’s the most important biological process on earth,” says Professor Susanne von Caemmerer. She’s the Deputy Director of the ARC Centre of Excellence for Translational Photosynthesis – a Canberra-based collaborative research centre focused on boosting crop yields through photosynthesis research.  

But it turns out not all photosynthesis types were made equal. About 95% of all plants grow using the most common type of photosynthesis; each cycle they take three carbon atoms to convert to organic molecules - hence it’s known as C3 photosynthesis.

However, a handful of crops are more efficient than that, and use four carbon atoms. This is called C4 photosynthesis, and it makes for a significant difference.

A whole new field

C4 photosynthesis was first discovered by Hal Hatch and Roger Slack at the Colonial Sugar Refining Company in Brisbane. They found that some crops – sugar cane, sorghum, and maize – use a different photosynthetic pathway to wheat and rice.

“The discovery of C4 photosynthesis created a whole new field in biology,” says Caemmerer.

While they make up only 4% of the plant species in the world, C4 plants are so efficient they do about 20% of the photosynthesis. These plants have a unique leaf structure, allowing them to grow up to five times larger, use less water, and thrive in warm climates.

Now, scientists are looking for ways to ‘hack’ the biology of C3 plants, to convert them to the C4 pathway. This could help boost production of major food crops, which is vital when climate change is threatening to make weather conditions increasingly hotter and drier.

“In the situation we’re in at the moment, globally, we need to increase our food production by about 70% to feed the burgeoning population,” says Professor Robert Furbank, director of ARC Centre of Excellence for Translational Photosynthesis.

“Plants that use the C4 photosynthesis pathway are the most productive plants on the planet, and the reason for this is that they are supercharged,” says Furbank. “They are like the Ferrari of the plant world.”

Hacking rice

This year marks the 50th anniversary of Hatch and Slack’s finding, and scientists are commemorating it this week with a conference in Canberra geared towards C4 photosynthesis.

One of their biggest research projects is focused on growing C4 rice. Funded by the Bill & Melinda Gates Foundation, it’s a global collaboration between 18 research teams.

“We see C4 rice as the first step,” says Professor Rowan Sage from the University of Toronto. By increasing the water efficiency of the plants, “it would allow rice to be grown away from fresh water paddies … with a very large increase in rice yield,” he explains.

Other prime candidates for a C4 ‘hack’ include cotton, wheat, soybeans and cassava. Switching more crops from C3 to C4 would reduce competition for land, water and fuel, says Sage. “It would reduce a lot of the agricultural footprint that humans have.”

While the supercharged crop research is still growing – they are aiming for C4 rice by 2030 – improvements in technologies such as CRISPR have helped move things along, “allowing us to leapfrog over evolution to accomplish this in a few decades, as opposed to a few million years, which is what nature took,” says Sage.

And while ongoing funding is always difficult to secure, the return on investment could be huge, and scientists are urging the world to take notice.

“If you could just give us the money you give for one high-performance jet, we could give you C4 rice, C4 cotton, and C4 wheat,” says Sage. “A $5 million investment could bring in trillions of dollars.” 

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