Molecular Structure and Function of Protective Plant Polymers

高等植物的叶和果皮主要起屏障作用，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的蜡和两种不溶的结构支撑聚合物之一，角质(用于航空器官)和苏贝林(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与细胞壁多糖相连，角质层表面的机械性能如何随着压力条件的变化而变化，以及Suberin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)采用化学和酶法制备柠檬果实角质蛋白和硬脂化马铃薯周皮的低聚物片段，进行层析分离，核磁共振和质谱分析鉴定。(2)对溶胀样品的核磁共振实验将被用来开发和应用方法，以确定酸橙水果角质、马铃薯伤口周皮、硫化绿棉和马铃薯硬化组织中的聚合物链结构、交联链和细胞壁连接。(3)将使用流变仪、原子力显微镜(AFM)和固态核磁共振来评估磨损、冷害和叶面施药对角质层机械性能和分子柔韧性的影响。(4)利用质构分析和核磁共振波谱研究了马铃薯块茎中沉积的硬聚合物的生物合成。该项目的总体目标包括了解保护性角质和Suberin生物聚合物的单体单元是如何连接在一起并与支撑细胞壁基质连接的，环境压力(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含水洗涤剂相互作用，以及Suberin或相关多酚在降解马铃薯质地的硬化过程中如何合成。归根结底，这项研究应该对农业和经济都有影响，有助于设计基本的作物保护战略。更广泛地说，从这项工作中发展出来的微观结构和分子洞察可能有助于工业或化妆品用合成防水材料的开发。最后，该项目将向植物学家社区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.