Unravelling novel mechanisms of starch granule biogenesis in potato

本项目将对马铃薯块茎发育过程中淀粉颗粒形成的机理进行研究。淀粉是植物储存碳水化合物的主要形式，作为我们饮食中卡路里的主要来源，对人类至关重要。尽管它很重要，但我们仍然不完全了解植物是如何产生淀粉的。在其天然形式下，淀粉形成由葡萄糖聚合物组成的不溶性颗粒。颗粒的大小因品种而异，并影响淀粉在烹饪过程中的物理和化学行为，以及最终食品的质地。最近，我们在理解淀粉颗粒在模式植物拟南芥和谷物叶片中启动（或启动）的机制方面取得了突破。在这些植物中，颗粒大小受每个质体产生的颗粒数的影响。然而，在淀粉作物中颗粒大小最大的马铃薯中，颗粒的形成尚未得到研究。从其他品种中获得的知识使得发现马铃薯颗粒大小和数量的控制尤为及时。此外，马铃薯淀粉颗粒具有明显的椭球形状，但决定颗粒形态的过程在任何物种中都不为人所知。本项目旨在探索淀粉颗粒形成和形态发生的分子机制。首先，我们将通过创建和研究每个起始蛋白的一系列缺陷突变体，研究哪些颗粒起始蛋白在发育中的块茎中建立正确的颗粒数量和大小。根据初步数据，我们将测试马铃薯中存在活跃颗粒形态形成的假设，该过程需要特定的起始蛋白异构体。最先进的3D电子显微镜和荧光显微镜将用于通过块茎发育详细研究淀粉体（淀粉合成和储存的质体细胞器）的结构-显示每个淀粉体通常启动多少颗粒，每个细胞的淀粉体数量，以及新的颗粒形成如何与新的淀粉体形成协调。作为促进进一步影响的最终目标，我们将使用该项目过程中产生的独特材料来评估颗粒大小和形态对淀粉在烹饪过程中的物理和化学行为的影响，淀粉的消化率，以及各种预制马铃薯食品的质地和感官品质。总之，该项目将极大地促进我们对马铃薯淀粉颗粒生物发生的基本机制的理解。

This project will develop a mechanistic understanding of starch granule formation in developing potato tubers. Starch is the major form in which plants store carbohydrates, and is vitally important to humankind as a major source of calories in our diet. Despite its importance, we still do not fully understand how plants produce starch. In its native form, starch forms insoluble granules that are composed of glucose polymers. The size of the granules is highly variable between species, and influence the physical and chemical behaviour of starch during cooking, as well as on the texture of the final food products. Recently, we have made breakthroughs in understanding the mechanism by which starch granules are initiated (or primed) in leaves of the model plant, Arabidopsis thaliana, and in cereal grains. In these plants, granule size is influenced by the number of granules initiated per plastid. However, granule initiation has not been investigated in potato, which contains the largest granule sizes among starch crops. The knowledge gained from other species make it particularly timely to discover the control of granule size and number in potato. Further, potato starch granules have a distinct ellipsoid shape, but the processes that determine the morphology of the granules are not understood in any species.This project aims to discover molecular mechanisms of starch granule initiation and morphogenesis. Firstly, we will investigate which of the granule initiation proteins establish correct granule number and size in developing tubers, by creating and studying a series of mutants defective in each initiation protein. We will then test the hypothesis that there is active granule morphogenesis in potato, based on preliminary data that this process requires a specific initiation protein isoform. State-of-the-art 3D electron microscopy and fluorescence microscopy will be used to study the structure of amyloplasts (the plastid organelle in which starch is synthesised and stored) in detail through tuber development - showing how many granules are typically initiated per amyloplast, the number of amyloplasts per cell, and how new granule formations are coordinated with new amyloplast formation.As a final objective to facilitate further impact, we will use the unique materials generated through the course of this project to assess the effects of granule size and morphology on the physical and chemical behaviour of starch during cooking, starch digestibility, as well as textural and sensory qualities in a variety of prepared potato food products. Overall, this project will greatly advance our understanding of fundamental mechanisms of starch granule biogenesis in potato.