RUI: Glucan Phosphatases and Regulation of Transitory Starch Metabolism

本研究项目的目标是了解淀粉在植物中的分解是如何在蛋白质水平上受到调节的。淀粉是植物的主要碳储存形式，是人类饮食中热量的主要来源，也是各种工业应用的重要原料。尽管淀粉在生物系统和人类社会中的重要性，但我们对淀粉代谢调节的理解却令人惊讶地有限，而且远远不够完整。瞬时淀粉是光合作用的主要产物，白天在植物叶片中积累，晚上降解，为细胞活动和植物生长提供能量。淀粉降解是一个复杂的过程，需要几个蛋白质家族的联合活性，包括葡聚糖磷酸酶、葡聚糖二激酶和淀粉酶。然而，关于这些蛋白质如何特异性地促进淀粉降解，还有许多未解之谜。本研究项目将探讨葡聚糖磷酸酶在启动和调节瞬时淀粉降解中的作用。全面了解控制淀粉降解的分子事件对于确定提高作物淀粉产量的新策略是必要的，淀粉是生物燃料和各种工农业应用的原料。从事该项目的本科生研究人员，其中一些将来自代表性不足和少数民族，将有机会从事结构生物化学和代谢组学研究，前往国家会议展示他们的工作，并与该领域的专家密切合作。因此，该项目将为下一代科学家提供指导和培训，并帮助留住在科学领域得不到充分服务和代表性不足的学生。本研究也将透过设计以专案为基础的实验课程，对生物化学本科教育有所贡献。总体而言，该项目代表了推进基础研究、改善本科教育和积极影响未来农业和工业应用的强大组合。淀粉是葡萄糖的不溶性聚合物。淀粉外层葡萄糖基残基被葡聚糖二激酶磷酸化，使淀粉颗粒部分水溶性，可被淀粉降解酶（如-淀粉酶）利用。随后葡聚糖磷酸酶去除磷酸基团是淀粉完全分解所必需的。通过采用多种结构、生物物理和生化技术，该项目将研究淀粉去磷酸化的各个步骤及其在调节淀粉降解中的未定义作用。具体来说，该项目旨在了解1)葡聚糖磷酸酶参与淀粉降解调控的机制；2)淀粉颗粒处葡聚糖去磷酸化的结构基础；3)淀粉去磷酸化在昼夜淀粉代谢中的关键作用。本项目将利用代谢组学方法，探讨非生物胁迫下淀粉磷酸化在淀粉代谢中的直接和间接作用。本研究项目的结果将有助于缩小在理解葡聚糖磷酸酶家族的作用和调节机制方面的知识差距。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this research project is to understand how starch breakdown in plants is regulated at the protein level. Starch is the major carbon storage form of plants, a main source of calories in the human diet, and an important raw material for various industrial applications. Despite the importance of starch in biological systems and in human society, our understanding of the regulation of starch metabolism is surprisingly limited and far from complete. Transitory starch, a primary product of photosynthesis, accumulates in plant leaves during the day, and is degraded at night to provide energy for cellular activities and plant growth. Starch degradation is a complex process that requires the combined activity of several protein families including glucan phosphatases, glucan dikinases, and amylases. However, there are many unanswered questions regarding how these proteins specifically contribute to starch degradation. This research project will investigate the role that glucan phosphatases play in initiating and regulating transitory starch degradation. A complete understanding of the molecular events that control starch degradation is necessary to define novel strategies to improve starch yields in crops, a raw material for biofuel and various industrial and agricultural applications. Undergraduate researchers working on this project, some of whom will be from underrepresented and minority populations, will be provided the opportunity to engage in structural biochemistry and metabolomics research, travel to national conferences to present their work, and collaborate closely with experts in the field. Thus, this project will provide mentorship and training for the next generation of scientists and help retain both underserved and underrepresented students in the sciences. This research will also contribute to biochemistry undergraduate education through the design of a project-based laboratory course. Overall, the project represents a robust combination of advancing foundational research, improving undergraduate education, and positively impacting future agricultural and industrial applications.Starch is an insoluble polymer of glucose. Phosphorylation of the starch outer glucosyl residues by glucan dikinases makes the starch granule partially water soluble and accessible to starch degrading enzymes such as -amylases. The subsequent removal of phosphate groups by glucan phosphatases is necessary for complete starch breakdown. By employing a variety of structural, biophysical, and biochemical techniques, the project will investigate the various steps in starch dephosphorylation and its undefined roles in regulating starch degradation. Specifically, the project aims to understand 1) the mechanisms by which glucan phosphatases contribute to the regulation of starch degradation; 2) the structural basis of glucan dephosphorylation at the starch granule; and 3) the critical roles of starch dephosphorylation in diurnal starch metabolism. By employing metabolomics, the project will explore the direct and indirect roles of starch phosphorylation in starch metabolism under abiotic stress. The results of this research project will help close the knowledge gap in understanding the roles and regulatory mechanisms of the glucan phosphatase family of enzymes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.