Long’s team broke photosynthesis down into a long series of mathematical equations and fed them to the National Center for Supercomputer Applications in Illinois. The supercomputer whirred through the numbers and spat out a list of “best-bet” interventions.
For example, one potentially easy win they identified was to dial up production of just a single protein known as sedoheptulose bisphosphatase, or SBPase. British researchers have already shown that tobacco plants engineered to express more SBPase grew 10% larger in a glasshouse. And if it works in them, Long says, then it is likely to work in any crop, since photosynthesis does not vary much among plants.
However, this is not the only way of increasing photosynthesis. Scientists are also exploring the idea that genes from the ancestors of modern-day plants might boost the ability of crops to harness the sun. It is well known that primitive plants known as cyanobacteria have a talent for concentrating CO2 within their cells at levels that make photosynthesis more efficient. It is believed that plants lost this ability when they transferred to the land 500 million years ago, because they did not need it.
Researchers at the Hebrew University of Jerusalem have evidence that this may be one key to increased yields. In trials, they achieved a 20% increase in tobacco plants after adding a single cyanobacteria gene called inorganic carbon transporter B (IctB). Long says that he and colleagues from the University of Nebraska have carried out some initial tests on soybeans transformed with the same gene, and have recorded a 10% increase in yield.
However, there is a long way to go before either of these techniques can be used in the field. There is huge opposition to genetically modified crops in many countries, with some groups citing safety concerns and others ethical, arguing that the developing world should not be used as a laboratory to test such crops. But even if these arguments are won and efforts to re-engineer photosynthesis succeed, Long admits it would take at least a decade to move these transformed plants from research settings to farm fields. It would also take a lot of money. “The cost of meeting global regulatory requirements for a single gene engineered into a crop can run into many millions,” says Long. “While we can show ways of achieving this, actually getting this to farmers could be more difficult.”
Turning the world green
Traditionally, farmers have sought out the best places to plant their crops – nutrient rich flood plains and the sides of volcanoes. But we have reached a point where all of this high quality land is taken. Instead, farmers are forced to use ever more marginal land – plots that are too wet, too dry, too short on vital nutrients, or are laced with damaging aluminium or salt.
As a result, there is a push to develop crops that not only grow in these conditions – they relish them. For example, researchers like Abdelbagi Ismail at the International Rice Research Institute (IRRI) in the Philippines are developing strains of rice that can flourish in flooded areas.
This is an important problem to tackle. As many as 20 million hectares of cultivated rice are affected by submergence in Asia every year.
To get round the problem, Ismail and his team scoured the vaults of their institute’s rice seed bank – the world’s largest with more than 110,000 varieties. They were looking for types of rice that survive on sketchy land, regardless of whether they produced low or high yields. In one case, they found a strain that did not waste precious energy trying to elongate itself above the waters when submerged by a flash flood, and instead put itself into a sort of temporary slumber. Using genetic techniques unavailable to Borlaug, they then crossed this flood-tolerant strain with a high-yield strain of rice.