Molecular Structure and Function of Fruit Cuticle Polyesters

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9728503 Stark The cuticle of higher plants functions primarily as a protective barrier for the leaves and fruit, controlling microbial attack as well as the diffusion of water and chemicals. Its major chemical constituents are waxes that provide waterproofing and either of two insoluble structural polymers, cutin and suberin. This project aims to understand how the monomer units are linked together and to cell-wall matrices, how stresses alter the membrane's supramolecular architecture and surface microstructure, and how the suberin polymer is synthesized during wound healing. Several biophysical approaches will be taken to these problems. (1) Oligomeric fragments of lime cutin and potato suberin will be produced chemically and identified using high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance (NMR). (2) The flexibility and phase segregation of intact tomato cuticles will be assessed in response to wind, temperature, and hydration stress using solid-state 13C and 2H NMR. (3) The response of tomato cuticle surface topography and micromechanical properties to dewaxing, swelling, and application of aqueous detergents will be examined using atomic force microscopy (AFM). (4) The biosynthesis of suberin in wound-healing potato tissues, including feeding with 13C-enriched precursors, will be monitored through spectroscopic analysis of soluble phenolic metabolities and insoluble cell-wall bound materials. 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, high humidity, and temperature shock alter the architecture of the cuticular membrane, and how the suberin polymer is synthesized by the plant tissue during wound healing. Ultimately, this research should have both agricultural and economic impact, aiding in the design of essential crop protection strategies. More b roadly, 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. ***