Elucidating the mechanism of starch granule initiation in developing wheat grains

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Despite its importance to humankind, we still do not fully understand how starch is made in plants. Starch is a complex carbohydrate that is composed of a large number of glucose units joined together into polymers, and is produced by plants as an energy store. It is found in leaves of most plants where it provides energy for growth at night, but it also accumulates in large amounts in many of our staple foods, such as wheat, rice and potato. Starch is therefore a major component of our diets, but it is also essential in manufacturing a variety of everyday items such as paper, textiles and pharmaceuticals. A full understanding of how plants make starch will lead to new ways of improving the nutritional value of our staple foods, with added health benefits, and also improving the quality of starch used for manufacturing.The polymers in starch assemble into insoluble 'granules'. While we have a good understanding of how the polymers in starch are synthesised, we do not yet understand how the process of making the starch granule begins in the plant. Without this knowledge of the granule initiation process, we can not understand what controls the number of granules that are made. The number of granules affects the size and shape of granules, which strongly influences how starch behaves during digestion, and also during manufacturing processes. Over the last decades, researchers have been using the model plant, a small weed named Arabidopsis thaliana, to better understand the starch synthesis process. Recently, I have made a breakthrough in understanding starch granule initiation in Arabidopsis leaves, and identified several new proteins involved in the process. Interestingly, all of these proteins are also present in other plants, including our staple crops such as wheat. Therefore, it is now time to move beyond the model and apply this new knowledge to our crops. The aim of this project is understand how starch synthesis is initiated in developing wheat grains. Using the latest advances in wheat genetics and breeding, I will find wheat mutants that do not have functional versions of the newly-discovered proteins involved in granule initiation. I will then study how the pattern of granule initiation changes within the developing grain as a result of the mutation. In parallel, I will also aim to discover new proteins involved in initiating starch granules in the grain by finding other proteins that bind to the existing ones. I will also study whether the wheat mutants have altered starch properties that are important for manufacturing food and non-food products. This will include tests for whether the flour milled from the grains have altered digestibility, which may alter the calorific value of foods. This research will contribute to the development of innovative crops in the UK, as it will lead to the development of new wheat varieties with altered starch properties that are healthier to eat, or of higher quality for use in manufacturing.