Photosynthesis by turbocharging in corn hikes gives

Scientists from the Boyce Thompson Institute (BTI) and Cornell have developed a carbon-inviting enzyme called RuBisCO to stimulate photosynthesis in corn. The discovery promises to be a key step in improving the efficiency and performance of agriculture, according to a new study conducted in Nature Plants on Oct. 1.

The increase in RuBisCO helps the organic machinery of corn used during photosynthesis to incorporate atmospheric carbon dioxide into carbohydrates.

"Every metabolic process – like photosynthesis – has the equivalent of traffic lights or speed bumps," said biologist David Stern, president of BTI. "RuBisCO is often the limiting factor for photosynthesis. With the increase in RuBisCO, however, this well known retarder is reduced, which improves the efficiency of photosynthesis.

RuBisCO has an official scientific name. It is ribulose-1,5-bisphosphate carboxylase / oxygenase, an enzyme that helps convert carbon dioxide into sugar. According to Stern, it is the most abundant enzyme on Earth.

But for the world of commercial farming and the C4 (four-carbon compound) photosynthesis system, RuBisCO is running slowly.

BTI researchers have found a way to overexpress a key chaperone enzyme called RuBisCO Assembly Factor 1, or RAF1, to help produce more RuBisCO.

"She needs the help of other proteins to assemble," said lead author Coralie Salesse, a Cornell doctoral candidate in the field of plant biology.

With the chaperone enzyme, scientists have indeed reduced a different slowdown – a slowdown in the rate at which RuBisCO can achieve the appropriate biological architecture – which leads the plants to accumulate more.

The exact mechanism of how RuBisCO was assembled was a mystery for many years, until the discovery of RAF1 and RAF2 proteins, said Salesse.

Salesse conducted research at Robert Sharwood and Florian Busch's laboratories at the Australian National University and Steven Long's laboratory at the University of Illinois. Salesse found that the increasing number of RuBisCOs meant that greenhouse plants flowered earlier, grew and produced more biomass.

"Corn is an important but intensive crop of land and energy, and it is important to reduce its environmental footprint. In this country alone, corn grows on about 90 million acres and nearly 15 billion bushels have been produced in recent years, "said Stern, an assistant professor of plant biology at Cornell. He explained that there are different approaches to increase biomass per acre, including increased photosynthesis, which could increase the weight of each ear of corn and thus give a yield per acre.

Stern noted – with this finding – that the same approach could be promising to improve yields in other C4 crops, such as sorghum and sugar cane.

"As we move from the greenhouse to the fields, we hope to see an improvement in the growth and yield of the production varieties," he said. "RuBisCO turbocharging has the potential to provide a basis for profound effects on the corn plant's ability to ripen and produce biomass, particularly when combined with other approaches.

Viktoriya Bardal of BTI, trainee at Stern Lab, and Johannes Kromdijk of the University of Illinois, are also authors of "Over-expression of Rubisco subunits with RAF1 increases Rubisco content in corn." Funding was provided by the US Department of Agriculture and the Mario Einaudi International Studies Center.