Molecular Structure and Biomechanics of Plant Cuticular Membranes

高等植物的角质层是外部环境中水和化学物质流动的多功能调节器，也是抵御细菌和真菌攻击的强大防御。蜡沉积在角质质聚酯上，而木质素和多酚类物质则在次生生长组织中发现或作为应激反应形成。水果角质层是智能表面——能够在空间上选择性地自我清洁，并在成熟过程中调节其最高的机械性能。为了在不破坏其独特特性的情况下建立这些卓越生物材料保护功能的分子和介观结构，将协调完整生物聚合物的固态核磁共振，生物力学分析和原子力显微镜，以检查共价结构和动力学，应力-应变曲线，粘弹性和表面拓扑结构。三个番茄果实角质层系统将被用来测试涉及角质层分子结构及其与蜡和细胞壁的组织对果实角质层机械完整性的影响的假设：一个去除表皮蜡以模拟环境胁迫的商业品种和两种具有遗传特征的角质层缺陷水果突变体。本项目的主题相关目标包括：优化完整果实角质层的结构和功能表征方法，测试蜡磨损应力下维持果实角质层完整性的机制模型，评估角质层/蜡的比例、数量和分支结构如何阻止角质层缺陷突变果实形成均匀屏障。以及对早熟脱水突变体中微裂的建筑原因和后果的测试。研究果实角质层完整性的多尺度方法在植物分子生物学家、遗传学家、物理化学家和生物工程师之间具有广泛的知识协同潜力。本研究结果将指导设计策略，以提高农业重要粮食作物的抗寒性和产量。这些卓越的天然植物界面的力学性能的发现也将启发自清洁涂料和纤维增强防水材料的仿生设计。为这项研究开发的新的核磁共振方法学将通过nsf赞助的研究协调网络传播。最后，这个项目的教育影响将包括大分子组装生物物理学的跨学科培训，在一个拥有超过60%西班牙裔和黑人学生的校园里进行，在一所授予近10%的美国非裔化学和化学工程博士学位的大学里进行。该项目将成为纽约市立大学两项新推广计划的基础，目标是附近的曼哈顿上城和布朗克斯高中，那里有大量少数民族人口：(1)一个学期的实验室植物生物聚合物课程，由纽约市立大学与纽约市教育部合作，为20名学生设计；(2)与CCNY的Pathways生物信息学和生物分子中心合作，举办40名学生的Gateway Lab研究培训讲习班。

The cuticle of higher plants serves as a versatile regulator of the flow of water and chemicals from the outside environment and a robust defense against bacterial and fungal attack. Waxes are deposited on a cutin polyester whereas suberin and poly(phenolics) are found in secondary growth tissues or formed as a stress response. Fruit cuticles are smart surfaces - capable of spatially selective self cleaning and regulation of their superlative mechanical performance during ripening. To establish the molecular and mesoscopic architectures underlying the protective functions of these remarkable biomaterials without destroying their unique properties, solid-state nuclear magnetic resonance, biomechanical analysis, and atomic force microscopy of the intact biopolymers will be coordinated to examine covalent structure and dynamics, stress-strain profiles, viscoelasticity, and surface topology. Three tomato fruit cuticle systems will be used to test hypotheses involving the influence of cutin molecular structure and its organization with waxes and cell walls on the mechanical integrity of fruit cuticles: a commercial cultivar from which epicuticular waxes have been removed to model environmental stress and two types of genetically characterized cuticle-deficient fruit mutants. The thematically related goals of this project include optimization of methods for structural and functional characterization of intact fruit cuticles, testing of mechanistic models for maintenance of fruit cuticle integrity under wax abrasion stress, evaluation of how cutin/wax ratios, amounts, and branched structures preclude formation of a homogeneous barrier in cuticle deficient mutant fruits, and testing of proposed architectural causes and consequences of microfissuring in precocious dehydration mutants.A multiscale approach to fruit cuticle integrity has broad potential for intellectual synergy among plant molecular biologists and geneticists, physical chemists, and bioengineers. The results of this research will guide the design strategies to enhance the hardiness and yield of agriculturally important food crops. Findings on the mechanical performance of these remarkable natural plant interfaces should also inspire the biomimetic design of self-cleaning paints and fiber-reinforced waterproofing. New NMR methodology developed for this research will be disseminated through an NSF-sponsored Research Coordination Network. Finally, the educational impact of this project will include interdisciplinary training in the biophysics of macromolecular assemblies, conducted on a campus that enrolls more than 60% Hispanic and Black students and at a university that awards almost 10% of U.S. African-American Ph.D.'s in Chemistry and Chemical Engineering. The project will form the basis for two new outreach initiatives based at CCNY and targeting nearby Upper Manhattan and Bronx high schools with substantial minority populations: (1) a semester-long lab-based Plant Biopolymers course designed for 20-student classes in CUNY's College Now partnership with the NYC Department of Education; and (2) a 40-student Gateway Lab research training workshop coordinated with CCNY's Pathways Bioinformatics and Biomolecular Center.