Plant Cell Wall Cellulose - Simple Polymer, Complexed Biosynthesis

植物在碳分配能力上具有固有的可塑性，这是有效调节生长发育的关键。此外，植物已经发展出一个复杂的调节系统，在一系列动态环境刺激下优化碳同化，这是塑造其适应性和生存的关键。研究表明，在不同物种中，叶片光合能力与叶面积生物量投资之间存在着进化上保守的关系。考虑到源组织（即成熟叶片）控制着植物发育所必需的碳水化合物的可用性，我们可以公平地假设初级代谢的产物因此复杂地参与了介导植物生长和发育的过程。蔗糖是代谢的核心，是通过光合作用产生的主要代谢物，在维管植物中是最常见的易位代谢物，最终为各种生物合成反应提供碳。在许多利用这些碳骨架的细胞过程中，细胞壁生物合成是一个重要的汇，并最终产生最终产物。细胞壁的化学和超微结构决定了植物的生理机能，更重要的是，影响了植物的形态、功能和适应性。曼斯菲尔德研究计划的长期目标是了解控制植物碳分配的复杂基本过程，以杨树（Populus spp.）和拟南芥为模式物种，特别强调控制碳水化合物代谢和植物细胞壁发育的生物合成过程的复杂性。这些信息是理解程序化细胞生长模式以及木质部发育（次生细胞壁）的复杂网络和调控框架的关键。拟议的研究建立在先前的发现基金的基础上，这些发现基金为待测试的假设奠定了基础。具体来说，这个拟议的研究计划包括一系列旨在解决以下问题的实验：1)活性纤维素沉积过程中udp -葡萄糖的来源是什么？2)“辅助”酶在纤维素生物合成中起什么作用？糖在汇组织中是如何维持稳态的？对资源分配的分子基础和植物次生细胞壁生物合成的复杂性的更深入了解，不仅有助于弥补我们在基础植物生物学方面的知识差距，而且有助于制定育种和/或工程植物策略，以最大限度地分配资源并应对气候变化。

Plants possess an inherent plasticity in their ability to allocate carbon, which is pivotal to the effective modulation of growth and development. Moreover, plants have developed a complex regulatory system to optimize carbon assimilation within an array of dynamic environmental stimuli that is key to shaping their fitness and survival. Across species, it has been shown that there is an evolutionarily conserved relationship between leaf photosynthetic capacity and biomass investment in leaf area. Given that source tissue (i.e., mature leaves) governs the availability of carbohydrates essential for plant development, it is fair to postulate that the products of primary metabolism are therefore intricately involved in mediating plant growth and development. Sucrose is central to metabolism and is the dominant metabolite produced via photosynthesis, and in vascular plants the most commonly translocated metabolite that ultimately provides carbon for a variety of biosynthetic reactions. Among the many cellular processes that draw on these carbon skeletons, cell wall biosynthesis is a significant sink and culminates in a terminal product. The resulting chemistry and ultrastructure of the cell walls defines the physiology of the plant and, importantly, impacts form, function and fitness. The long-term objectives of the Mansfield research program is to understand the complex fundamental processes that govern carbon allocation in plants, using poplar trees (Populus spp.) and Arabidopsis as model species, with a specific emphasis on the intricacies of the biosynthetic processes governing carbohydrate metabolism and plant cell wall development. This information is key to understanding programmed cellular growth patterns, and the complex network and regulatory frameworks fundamental to xylem development (secondary cell walls). The proposed research builds on previous Discovery Grants that formed the foundations of the hypotheses to be tested. Specifically, this proposed research program is comprised of a series of experiments aimed at addressing the following questions: 1) What is the source of UDP-glucose during active cellulose deposition? 2) What role do “accessory” enzymes have in cellulose biosynthesis? 3) How is sucrose homeostasis maintained in sink tissues? A greater understanding of the molecular underpinnings of resource allocation, and the intricacies of plant secondary cell wall biosynthesis will contribute, not only to our knowledge gaps in fundamental plant biology, but also could facilitate strategies for breeding and/or engineering plants to maximize resource allocation and combat a changing climate.