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系统。蜡质沉积在角质聚酯上，而Suberin和多酚类物质则存在于次生组织中或作为胁迫反应而形成。水果角质层是一种智能表面--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。为了在不破坏生物材料独特性能的前提下建立起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-应变分布、粘弹性和表面拓扑。三个番茄果实角质层系统将被用来检验涉及角质分子结构及其与蜡质和细胞壁的组织对果实角质层机械完整性的影响的假说：一个商业品种已经去除了表皮层蜡质以模拟环境胁迫，以及两种具有遗传特征的角质层缺陷水果突变体。该项目的主题相关目标包括优化完整水果角质层结构和功能表征的方法，测试在蜡质磨损压力下维持水果角质层完整性的机械模型，评估角质/蜡的比例、数量和分枝结构如何阻止角质层缺失突变水果形成同质屏障，以及测试所提出的结构原因和早熟脱水突变体微破裂的后果。水果角质层完整性的多尺度方法在植物分子生物学家和遗传学家、物理学家和生物工程师之间具有广泛的智力协同潜力。这项研究的结果将指导提高农业重要粮食作物的抗逆性和产量的设计策略。这些非凡的天然植物界面的机械性能的发现也应该启发自清洁涂料和纤维增强防水的仿生设计。为这项研究开发的新的核磁共振方法将通过NSF赞助的研究协调网络进行传播。最后，该项目将对教育产生影响，包括在一个招收60%以上拉美裔和黑人学生的校园以及一所授予近10%美国非裔美国人化学和化学工程博士学位的大学里，开展大分子组装生物物理学方面的跨学科培训。该项目将成为CCNY两项新的外展计划的基础，并针对曼哈顿上城和布朗克斯附近少数民族人口较多的高中：(1)为期一学期的以实验为基础的植物生物聚合物课程，在CUNY学院为20名学生的课程设计，现已与纽约市教育部合作；以及(2)与CCNY的路径生物信息学和生物分子中心协调的40名学生的Gateway实验室研究培训研讨会。

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.