Molecular Structure and Function of Protective Plant Polymers

高等植物的叶和果实表皮主要起屏障作用，控制细菌和真菌的侵袭以及来自外部环境的水和化学物质的扩散。 它们的主要化学成分是提供防水性的蜡和两种不溶性结构支撑聚合物中的任一种，角质（用于空中器官）和木栓质（在内部位置和伤口组织中）。 该项目旨在了解生物聚合物的单体单元如何共价连接在一起并连接到细胞壁多糖，表皮表面的机械性能如何响应应力条件而变化，以及木栓质或相关材料如何参与马铃薯组织的质地硬化。 将采取几种生物物理方法来解决这些问题。 (1)酸橙果实角质和木栓化马铃薯伤口周皮的寡聚片段将通过化学和酶方法产生，色谱分离，并通过核磁共振（NMR）和质谱（MS）鉴定。 (2)溶剂溶胀样品的NMR实验将用于开发和应用方法，以确定聚合物链结构，交联，和细胞壁连接在石灰果角质，马铃薯伤口peridendum，木栓化绿色棉花，和硬化马铃薯组织。 (3)磨损，冷害，和叶面输送农药对角质层的机械性能和分子的灵活性的影响将使用流变仪，原子力显微镜（AFM），和固态NMR进行评估。 (4)硬聚合物的生物合成沉积在马铃薯块茎，有“难煮综合征”将研究使用质地分析和核磁共振光谱。该项目的总体目标包括了解保护性角质和木栓质生物聚合物的单体单元如何连接在一起并支持细胞壁基质，环境应力（如风磨损和温度冲击）如何改变角质膜的机械性能，水果角质层如何与农用化学品应用中使用的水性洗涤剂相互作用，以及木栓质或相关多酚在使马铃薯质地变差的硬化过程中是如何合成的。 最终，这项研究应具有农业和经济影响，有助于设计基本的作物保护战略。 更广泛地说，从这项工作中开发的微观结构和分子见解可能有助于工业或化妆品用合成防水材料的开发。 最后，本项目将向植物科学家介绍固体核磁共振和原子力显微镜等方法。

The leaf and fruit cuticles of higher plants function principally as barriers, controlling bacterial and fungal attack as well as the diffusion of water and chemicals from the outside environment. Their major chemical constituents are waxes that provide waterproofing and either of two insoluble structural support polymers, cutin (for aerial organs) and suberin (at internal locations and in wound tissue). This project aims to understand how the monomer units of the biopolymers are covalently linked together and to cell-wall polysaccharides, how the mechanical properties of the cuticular surface change in response to stress conditions, and how suberin or related materials are involved in textural hardening of potato tissues. Several biophysical approaches will be taken to these problems. (1) Oligomeric fragments of lime fruit cutin and suberized potato wound periderm will be produced by chemical and enzymatic means, separated chromatographically, and identified by nuclear magnetic resonance (NMR) and mass spectrometry (MS). (2) NMR experiments on solvent-swelled samples will be used to develop and apply methodologies to identify polymer chain structures, cross-links, and cell-wall linkages in lime fruit cutin, potato wound periderm, suberized green cotton, and hardened potato tissues. (3) The impact of abrasion, chilling injury, and foliar delivery of pesticides on cuticular mechanical properties and molecular flexibility will be assessed using rheometry, atomic force microscopy (AFM), and solid-state NMR. (4) The biosynthesis of hard polymeric substances deposited in potato tubers that have 'hard-to-cook syndrome' will be studied using texture analysis and NMR spectroscopy. The overall objectives of this project include understanding how the monomer units of the protective cutin and suberin biopolymers are linked together and to supporting cell-wall matrices, how environmental stresses such as wind abrasion and temperature shock alter the mechanical properties of the cuticular membrane, how fruit cuticles interact with aqueous detergents used in application of agrochemicals, and how suberin or related polyphenols are synthesized during the hardening process that degrades potato texture. Ultimately, this research should have both agricultural and economic impact, aiding in the design of essential crop protection strategies. More broadly, the microstructural and molecular insights developed from this work may assist the development of synthetic waterproofing materials for industrial or cosmetic use. Finally, this project will serve to introduce methods such as solid-state NMR and AFM to the community of plant scientists.