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The Golden Revolution

With the famed Green Revolution running out of puff, scientists are working on a new Golden Revolution that will deliver a step-change in agricultural output.

We’ve all been the beneficiaries of the Green Revolution, an application of breeding and agrochemical technologies that dramatically improved crop yields after World War II.

Driven by the Nobel Peace Prize-winning Professor Norman Borlaug, this revolution was the world’s new approach to farming, setting the benchmark for modern agricultural practices and applying the scientific method to get the most out of crops.

Targeted crop breeding enlisted semi-dwarfing and disease resistance, drought resistance and waterlogging resistance genes from different crop varieties to maximise productivity under a vast array of farming conditions, and the hard graft of farmers worldwide delivered more food to the table.

The Green Revolution brought about dramatic improvements in the efficiency of sunlight capture by crops, with plants rapidly forming full canopies that could efficiently use the incoming light. Short-statured plants deliver more of the sugar they produce into the grain rather than their shoots.

But we are almost at the limit of these improvements. There is a recognition among plant and agricultural scientists internationally that bottlenecks to further crop improvement are approaching and that a new Golden Revolution is needed to ensure food security in the future.

One key focus is to improve the efficiency of photosynthesis, the means by which plants use sunlight energy and carbon dioxide from the atmosphere to generate sugars and oxygen. Photosynthesis is the key process that fuels not only grain production but almost all life on the planet. Yet, it has
its problems.

In plant leaves, an enzyme called Rubisco is responsible for trapping carbon dioxide and building sugar molecules, but it is extremely slow and often confuses carbon dioxide for oxygen, leading to energy-wasting processes which come at a cost to grain production. For example, estimates suggest this process costs US soybean yield approximately 36 percent annually.

For this reason, improving Rubisco has been a target of plant science research for decades, and it has been a tough nut to crack. But with the development of new technologies and an ever-increasing understanding of plant biology, scientists are making headway on this challenge, and it could change the face of agriculture.

There are several solutions to the Rubisco problem, and scientists are looking to nature as a source of inspiration.

Cyanobacteria (better known as blue-green algae, though best thought of as photosynthetic bacteria) evolved a clever solution to the slow and promiscuous Rubisco enzyme hundreds of millions of years ago.

We best know cyanobacteria for their ability to generate toxic blooms in lakes and rivers. A major reason for their ability to do this is that they utilise a specialised system to support their Rubisco enzyme, called a carbon dioxide concentrating mechanism.

This mechanism pumps CO2 to high levels around Rubisco, increasing the speed it can produce sugars and decreasing the rate that the energy-wasting oxygen reaction can occur. This leads to rapid growth with potentially harmful results, but there is a silver lining to this toxic blue-green cloud.

While crop plants invest heavily in producing large amounts of Rubisco to maximise CO2 conversion into sugar, cyanobacteria have invested in a turbo CO2 capturing engine that comes at low cost but operates at high speed. It offers tantalising possibilities in terms of crop performance.

At the Australian National University, we have been studying these CO2 concentrating mechanisms for several decades to understand their complex structure and function. We’ve teased apart the intricate processes cyanobacteria use to make this mechanism work, and identified the key components.

The Green Revolution used 20th-century breeding techniques to slowly,  and with low precision, introduce new genes to modify crop plant performance. It was, for the most part, untargeted and often led to the improvement in one trait and the loss of another. The Golden Revolution of agriculture will use targeted improvements in crop production to deliver a step-change in agricultural output.

As part of an international research consortium, we are working to generate crop plants which utilise a synthetic cyanobacterial turbo photosynthesis system, enhancing the efficiency of sugar production far beyond what could have been achieved through traditional breeding methods.

The genes for this system don’t exist in any plants, but new technologies enable us to produce such a system with bespoke, tailored design. Computational models have predicted it could improve crop yields by more than 30 percent and save on both water and nitrogen fertiliser.

Our work is part of a broader international research consortium, identifying inefficiencies in photosynthesis and improving upon them. This Golden Revolution uses the newest technologies available to make novel, synthetic systems in crop plants which we hope will transform agriculture and secure food for future generations.

This article was written for Rural Business by Ben Long, who is a Senior Research Fellow at The Australian National University in Canberra. His research focuses on applying cyanobacterial CO2 concentrating mechanisms to improve food crop production as part of the Realising Increased Photosynthetic Efficiency (RIPE) project.

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