US: New Light On Photosynthesis Raises Hopes Of New Green Revolution

Source from:  Financial Times 01/04/2019

US researchers have reached a landmark on the path to what they say will be the next agricultural revolution, significantly boosting crop growth by making photosynthesis more efficient.

The team at the University of Illinois and the US Agricultural Research Service overcame a natural fault in photosynthesis, the conversion of solar energy into biomass, through genetic engineering.

Engineered tobacco plants were “40 per cent more productive in real world agronomic conditions” than unaltered specimens, according to the results of field trials published in Science.

The researchers used tobacco for the initial experiments because it is a model plant whose genetics are well understood. This year they will transfer the technology to the potato, which is closely related to tobacco, and then move on to other important food crops including soya, rice and cereals.

“We are very excited,” said Paul South, the project leader. “The increase in biomass we have seen in our field trials is more than we expected.”

Crop productivity is currently improving by less than 2 per cent a year — not fast enough to feed the growth in global population expected in coming decades.

To accelerate improvements in food productivity, the Bill & Melinda Gates Foundation, US Foundation for Food and Agriculture Research and UK Department for International Development are jointly investing $58m in a five-year research programme called Ripe (Realising Increased Photosynthetic Efficiency).

The Illinois scientists have achieved the programme’s most impressive field trial results so far, though other Ripe researchers are also reporting encouraging data with different approaches.

Transferring the technology to food crops and obtaining regulatory approval is likely to take more than a decade. Although the agricultural biotechnology industry will be involved in commercialisation,

Ripe’s funding organisations “are committed to ensuring that smallholder farmers, particularly in sub-Saharan Africa and south-east Asia, will have royalty-free access to all of the project’s breakthroughs”.

An important reason for the inefficiency of photosynthesis is that a competing process known as photorespiration consumes energy that might otherwise contribute to plant growth. The Illinois team greatly reduced the process’s calorie consumption by re-engineering the natural biochemical pathways involved in photorespiration.

“We could feed up to 200m additional people with the calories lost to photorespiration in the Midwestern US each year,” said Donald Ort, Illinois professor of plant science. “Reclaiming even a portion of these calories across the world would go a long way to meeting the 21st century’s rapidly expanding food demands, driven by population growth and more affluent [societies’] high-calorie diets.”

At the heart of photosynthesis is an enzyme called Rubisco, which enables cells to make carbohydrates from carbon dioxide and water in sunlight. Rubisco evolved in simple photosynthesising organisms aeons ago, when oxygen levels in the atmosphere were very low.
Under present conditions the enzyme mistakenly grabs an oxygen molecule rather than carbon dioxide from the air about 20 per cent of the time. This produces compounds that are toxic to plants and have to be recycled through the energy-hungry photorespiration process.

“Photorespiration is anti-photosynthesis,” said Mr South. “It costs the plant precious energy and resources that it could have invested in photosynthesis to produce more growth and yield.”

Through synthetic biology, the Illinois team drastically simplified the long and complex biochemical route that photorespiration normally takes, allowing the plant to devote more energy to building up its roots, stems, leaves, flowers and seeds.  Enditem