IWYP Call 2: Manipulating stomatal blue light response in wheat to improve productivity

World demand for food is growing and it has been estimated that a 50% increase in yield will be needed to meet the increasing demand due to the growing world population. This situation is further exacerbated by the changing climate, with predictions of reduced water availability in some regions and flooding in others. The anticipated increase in global temperature will reduce plant productivity as well as increase plant demands for water. Photosynthesis is the process by which plants use the energy from the sun to convert carbon dioxide (CO2) from the atmosphere into carbohydrates and other chemical compounds, which are used for growth. Photosynthesis takes place in all green parts of plants and in order for leaf photosynthesis to take place CO2 must enter the leaf through adjustable pores, called stomata, and at the same time water is lost through these pores which also aids in cooling the leaf down. It is important to maintain an optimal leaf temperature for photosynthesis, as high temperatures greatly reduce photosynthesis and crop yield. However if too much water is lost the plant will wilt and eventually die. Stomata are continually adjusting to changing environmental conditions to balance CO2 uptake with water loss. Stomata open in response to increasing light, however this response depends on the wavelength of light, and generally two different responses have been identified. The first is named the "red" light or mesophyll response. This response occurs during high light levels and is linked directly to the rates of photosynthesis; the second is the "specific blue" light response, which occurs at low light levels, such as those found early in the morning or late in the evening. Reducing stomatal sensitivity to blue light has the potential to optimise the crop's resource use, thereby maintaining photosynthetic rates while using water more efficiently. Decreasing water use will enable sustained photosynthetic rates through the grain filling period when water becomes limiting, thus enhancing overall photosynthetic potential of the crop throughout the cycle and increasing grain yield. We will use a non-transgenic tilling approach to identify single mutations in a gene known to be essential in stomatal responses to blue light (BLUS1) in each of the wheat homoeologs (A, B and D) and use these to generate single, double and triple mutants in a variety of different backgrounds. Mutants generated will be phenotyped for gas-exchange, photosynthetic biochemistry and grain yield production in both controlled environment conditions and 2 different field environments.

Stomatal behaviour controls photosynthesis, water use and leaf temperature and these leaf pores are therefore an important, and unexploited, target for manipulation to improve crop productivity. Stomata open in response to increasing light, and two different responses have been described according to the wavelength of light. The first is named the "red" light or mesophyll response, occurs at high light levels and is linked directly to the rates of photosynthesis. The second is the "specific blue" light response and saturates at light levels too low to drive photosynthesis, which leads to stomata being more open than needed to achieve maximum CO2 uptake for photosynthesis; therefore the ratio of carbon gain to water loss, known as water use efficiency (WUE), is reduced. Reducing stomatal sensitivity to blue light has the potential to optimise the crop's resource use, thereby maintaining photosynthetic rates while using water more efficiently. Decreasing water use will enable sustained photosynthetic rates through the grain filling period when water becomes limiting, thus enhancing overall photosynthetic potential of the crop throughout the cycle and increasing grain yield. We will use a non-transgenic tilling approach to manipulate stomatal responses to blue light use these to generate a variety of different mutant backgrounds.
From this work we will deliver non-transgenic wheat plants with improved photosynthetic capacity throughout the crop cycle combined with better water use, and maximized productivity under a range of environmental conditions
These results will feed into existing breeding pipelines and the outcomes of this research will be of benefit to developing countries, contributing to sustainability and resource use efficiency through the production of cultivars with varying stomatal conductance, leaf temperatures and water use efficiencies, which will be advantageous for maximal growth in a range of different agricultural environments.

Not applicable - see case for support