The regulation of starch biosynthesis and intermediary metabolism in plants

淀粉是一种不溶性聚合物，在地球上大多数植物的碳经济中起着至关重要的作用。它由两种葡萄糖聚合物组成：线性直链淀粉，它的合成只需要一种酶；高度支支链淀粉越多需要的协调活动的产品至少10基因。淀粉是玉米、小麦和水稻等驯化谷物产量的主要决定因素，其高热量含量对人类和动物的消费都至关重要。在非食品工业中，它也是一种重要的商品，其功能依赖于葡萄糖残基在严格定义的半晶体结构中的组织，其组装仍然知之甚少。淀粉代谢支持植物遗传和代谢决策之间的相互作用，决定发育过程的时间和启动，包括开花和种子生产。它的动员对植物的生长至关重要，我们开始明白，影响来源组织中它的合成和结构可以对生产力产生重大影响。我的研究重点是了解：1)负责淀粉合成和结构的生化和分子机制2)植物如何分配资源来支持生长和发育。我们已经证明，参与淀粉生物合成的几种酶形成异聚物复合物，在物理和协同作用下共同产生淀粉的主要成分支链淀粉。这些复合物的组装在翻译后由位于发育中的种子的淀粉体或叶片的叶绿体中的蛋白激酶控制。最近我们发现，通过改变模式植物拟南芥中参与支链淀粉合成的淀粉分支酶的特定亚型，不仅可以改变支链淀粉的结构，而且可以在生物量和种子产量方面产生深刻的积极变化，为提高油料作物的产量提供了新的机会。我们还发现了一个非催化亚基的全球代谢调节剂SnRK1，它对碳水化合物的利用有显著影响，并整合了有机酸、脂质和硝酸盐的吸收的代谢。因此，本提案的主要目标是：1)了解翻译后机制如何影响淀粉产生的数量和结构；2)确定支持淀粉有效利用的分子，生理和生化决定因素；3)研究代谢的全局调节因子在控制资源和营养物质分配中的作用。我们已经准备好提供这样的知识，为作物生物工程提供机会，以应对全球人口迅速增长的挑战。

Starch is an insoluble polymer that plays a critical role in the carbon economy of most plants on earth. It is composed of two glucose polymers: linear amylose, whose synthesis requires just a single enzyme; and the more highly branched amylopectin which requires the coordinated activity of the products of at least 10 genes. Starch is the major determinant of yield in domesticated cereals such as maize, wheat, and rice, whose high caloric content is critical for both human and animal consumption. It is also an important commodity in non-food industries where its functionality is dependent on the organisation of glucose residues within a tightly defined, semi-crystalline structure, the assembly of which remains poorly understood. Metabolism of starch underpins the interplay between genetic and metabolic decision-making in plants, dictating the timing and initiation of developmental processes including flowering and seed production. Its mobilisation is critical for the growth of plants, and we are beginning to understand that affecting its synthesis and structure in source tissues can have significant effects on productivity. My research is focussed on understanding: 1) the biochemical and molecular mechanisms which are responsible for starch synthesis and architecture 2) how plants allocate resource to support growth and development. We have shown that several enzymes involved in starch biosynthesis form heteromeric complexes, working together physically and synergistically to produce the major component of starch, amylopectin. Assembly of these complexes is controlled post-translationally by protein kinases located within either amyloplasts of developing seeds or chloroplasts of leaves where starch is made. Recently we discovered that by changing the particular isoforms of starch branching enzymes involved in amylopectin synthesis in the model plant, Arabidopsis thaliana, not only was it possible to modify the structure of amylopectin, but there were profound, positive changes in biomass and seed production offering new opportunities to enhance the yield of oilseed crops. We have also identified a non-catalytic subunit of a global regulator of metabolism, SnRK1, which has significant effects on the utilisation of carbohydrate and integrates the metabolism of organic acids, lipids and the uptake of nitrate. Thus the main goals of this proposal are to 1) understand how post-translational mechanisms affect both the amount and structure of starch produced 2) identify the molecular, physiological and biochemical determinants which underpin the effective utilisation of starch for growth and development 3) investigate the role of global regulators of metabolism in controlling allocation of resources and nutrients to growth. We are well-poised to deliver such knowledge, providing opportunities for crop bioengineering to meet the challenges of a burgeoning global population.