Thomas Hughes is a PhD researcher at Oxford University’s Department of Plant Sciences, who has recently completed a 3 month internship with 3Keel. His research is focused on improving future rice yields. In this blog he outlines the challenge.
Rice is arguably the world’s most important crop, as virtually all is used directly for human consumption, often in some of the world’s poorest regions. But after rapid increases in the 20th century, rice yields are now plateauing, while population pressures continue to rise. In southeast Asia where rice is the key staple, every hectare of agricultural land currently has to support 27 people, and by 2050 it’s projected that this will rise to 43. Finding new ways to increase rice yields is an important part of tackling the food security challenge.
All of our food ultimately relies on the ability of plants to utilise sunlight to convert carbon dioxide into sugar, a process known as photosynthesis. In common with many of our most important crops such as wheat, potato and soybean, rice uses a type of photosynthesis termed ‘C3’. However, C3 photosynthesis is inherently inefficient. This is because the enzyme responsible for capturing CO2 (named Rubisco) is actually unable to distinguish well between carbon dioxide and oxygen, meaning the plant has to deal with lots of unnecessary and wasteful reactions.
In order to increase rice yields by the required 50%, it’s likely that we’re going to have to find ways of overcoming the inefficiencies of C3 photosynthesis. One strategy to do this is to take inspiration from innovations already found in nature – for example ‘C4’ photosynthesis. Plants that evolved C4 are able to pump carbon dioxide into a specialised compartment where Rubisco is exclusively localised. This ensures that Rubisco is saturated with carbon dioxide, and doesn’t have to worry about confusing it with oxygen. This so-called carbon concentrating mechanism enables C4 species to exhibit 50% higher yields, as well as significantly enhanced water and nitrogen use efficiencies.
Recently, a group of researchers around the world have joined together to investigate the possibility of introducing C4 photosynthesis into rice. This consortium, funded by the Bill and Melinda Gates Foundation, is coordinated from the International Rice Research Institute (IRRI) in the Philippines, and brings together expertise from a diverse range of disciplines. My PhD here in Oxford is focused on developing our understanding of what triggers a plant to develop C4 at the start of its lifecycle, drawing insights from maize, a crop which already uses the C4 strategy. The hope is that if we can understand this process more fully, it should aid us in future attempts to engineer rice to use C4 photosynthesis.
In order to increase rice yields by the required 50%, it’s likely that we’re going to have to find ways of overcoming the inefficiencies of C3 photosynthesis. One strategy to do this is to take inspiration from innovations already found in nature – for example ‘C4’ photosynthesis.