Rewinding evolution to capture the sun

In a bid to ensure food security through productive, disease-resistant plants, researchers from the ARC Centre of Excellence in Synthetic Biology had proposed a radical solution: turn back the evolutionary clock.

Plants convert light to energy through photosynthesis, and the more efficient this process is, the better they generally grow.

In a paper, published in Nature Communications, Dr Briardo Llorente and colleagues describe a way to move genes around to optimise photosynthesis and make super-productive plants. This involves reversing the evolutionary processes that shaped critical organelle that convert light to energy. 

“Achieving sustainable food security is one of the most significant challenges of our time,” says Llorente. “This has to be accomplished in the face of global climate change causing increasingly severe environmental stresses and more frequent plant disease outbreaks affecting crop yields.”

What are chloroplasts?

Chloroplasts – organelle responsible for photosynthesis – evolved from a light-eating bacterium and merged with another plant-ancestor cell more than a billion years ago. Over evolution, the bacterium transferred many of its genes into the genome of its host. This resulted in chloroplasts that rely on communication with the nuclear genome – where all the genetic information is stored – to ask for more resources.

Unfortunately, this also limits crop yield because pathogens can interrupt this cellular communication and cause disease.

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A core process in plant evolution has been the transfer of chloroplast-encoded genes to the nuclear genome. Reverting this process by relocating genes from the nucleus to the chloroplast could enable crop productivity and sustainability. Credit: Briardo Llorente/Sketching Science

“At the moment, we are up against several problems with modern-day agriculture,” says Llorente. “One of them is that pathogens pose a constant threat to food security. Breeding crops with protective qualities is a time-consuming and expensive process. Achieving long-lasting protection against pathogens is also challenging because pathogens often adapt rapidly to overcome resistance.”

When communication is interrupted, the chloroplasts tell the nucleus what resources they need, but the nucleus can’t give a tailored response – instead, the nucleus takes a democratic approach and diverts resources elsewhere instead of prioritising the chloroplast.

“Our approach, which we think could have quite a drastic impact, opens new ways to develop plants that are more resistant to pathogens and capable of improved photosynthesis,” says Llorente.

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Elodea (an aquatic plant) at 100X magnifiction. The green dots are chloroplasts. Credit:
Ed Reschke / Getty Images.

Rewinding evolution?

This method involves relocating the important genes into the chloroplast’s genome, so they can independently make decisions to boost productivity of photosynthesis – thus ‘rewinding evolution’ so the chloroplasts act like the original bacterium did back in the day.

“And in conferring chloroplasts more autonomy, we could allow each chloroplast to adapt its photosynthetic processes according to its individual functional and physiological needs, something that could lead to overall improved plant photosynthesis,” says Llorente.

“We need to design our future crops to have significant gains in yields while simultaneously reducing agriculture’s environmental impact in the general context of climate change.”

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