Unlocking the potential of C4 rice
ANU researchers are searching genes linked to photosynthetic pathways with potential applications in the development of more efficient crops. If we can use GM technology to make these pathways (and hence plants) more efficient, will this be acceptable to the general public?
The following has been reprinted with permission from Australian National University’s Science Wise Magazine. The full article can be viewed here. I have reprinted it because of all the media chatter and high profile people such as United Nations secretary-general, Ban Ki-Moon’s comment that failure at next month’s international climate change negotiations would result in a rise in hunger. In my community presentations on GM foods, even people who have relatively high concerns about GM foods will tend to find acceptable GM crop examples I present that are drought tolerant. I would be curious to know that if the ANU research below leads to the creation of GM crops altered to have a more efficient photosynthetic pathway would such crops be acceptable to the public and why or why not?
Unlocking the potential of C4 rice (ScienceWise November/December 2009)
The United Nations Food Agency recently announced that over the coming 40 years the world’s food production will need to rise by 70% in order to feed the growing population. Failure to achieve this is likely to result in widespread famine. This in turn, may well lead to unrest that spreads well beyond the borders of the most affected nations, so in reality, it’s likely to become everyone’s problem. The difficulty the world faces in addressing this is that most of the viable agricultural land is already used to capacity and production is limited by other factors such as water availability. The general consensus amongst scientists is that the only practical way to avert catastrophe is to enhance the photosynthetic yield per leaf area of food crops. In other words, to create more efficient plants.
Most plants, including many staple foods like rice, turn sunlight into sugar using what’s known as the C3 photosynthetic pathway. In this process gaseous CO2 is combined with an enzyme called RuBisCO to create sugar. However RuBisCO can and often does, combine with oxygen instead of CO2, leading to a loss of efficiency particularly at higher temperatures.
Some more recently evolved plants have developed an alternate photosynthetic pathway called C4 that avoids this loss of efficiency by using some additional chemistry to saturate the RuBisCO enzyme with CO2 and starve it of oxygen. This avoids wasteful oxygen combinations and under most environmental conditions, leads to a higher sugar yield in the plant. Scientists believe that if they can introduce this C4 photosynthesis to rice, they may be able to create cultivars that produce more crop per area than existing rice without consuming more water or fertilizer.
One scientist studying the possibilities of C4 rice is Professor Susanne von Caemmerer of the Research School of Biology. Professor von Caemmerer is working on a project with the International Rice Research Institute, sponsored by a $10m grant from the Bill and Melinda Gates foundation. The ultimate aim of this work is to create C4 rice with a substantially better yield than existing plants, but this is a hugely complex task requiring multiple steps.
The basic idea is to look at millions of mutant seedlings of both C3 rice and C4 sorghum. Scientists expect the random mutations to cause some of the rice to move towards the C4 pathway and some of the sorghum to partially revert to the C3. If they can identify which specimens these transformations take place in, they can analyse their genomes and compare them to conventional rice and sorghum. Seeing both the C3-C4 and C4-C3 switch should help them to isolate the genes responsible for the two photosynthetic pathways.
“Ultimately, this is a gene discovery project. We’re hoping to isolate mutants that appear to switch photosynthetic pathways. What we can then do is look at the genome of those plants and try to identify which genes are responsible for C4. This would be a huge help to another arm of the project in which scientists would directly splice those genes into existing rice cultivars,” says, Professor von Caemmerer.
Jason Major