EXPLORING THE BIOSYNTHESIS OF PLANT FATTY ACID-BASED POLYMERS

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The interactions of plants with the environment begin at their surface. Plant surfaces are covered by lipid barriers that contain a core structure of polyesters derived from hydroxy fatty acids: cutin and suberin. Cutin and waxes form the cuticle that covers the aerial primary surfaces of plants. Suberin is found on cork cell walls of tree bark, tuber skin, seed coats, and root periderm. These natural defenses protect plants against pathogens, salinity, and drought. Although lipid polyesters are critical to the subsistence and performance of all agricultural and forestry species, there are key unknowns in our understanding of their biosynthesis and structure. Research proposed in this grant application will (1) enhance our understanding of the biosynthesis and structure of suberin and cutin, and (2) define the enzymology of lipid polyester synthesis using a novel system, the wet stigmas of Solanaceous species. Multidisciplinary approaches will be used. Arabidopsis, poplar and potato mutants will be employed to address questions on polyester structure. Biochemical approaches will use developing stigmas of tobacco, which produce an exudate rich in hydroxy fatty acid polymers that, unlike cutin, are soluble in organic solvents and experimentally easier to analyze. Genomic approaches will involve transcriptome analysis of developing tobacco stigmas. Candidate genes will be tested by gene silencing and by gene overexpression in tobacco and petunia stigmas. One long-term goal of this research program is to manipulate the composition of plant polyesters to improve desirable agronomic crop traits, including resistance to biotic and climatic stresses, modification of seed dormancy, and improvement of seed viability. Research in Arabidopsis is applicable to close relatives such as canola, whereas the Solanaceae family includes major crop species, for example tomato and potato. In addition to its potential impact on agricultural production, the work proposed involves important industrial products, polyesters and their monomers, omega-hydroxy fatty acids. Understanding stigma polyester assembly may lead to ways of producing these materials more abundantly in plants or in microbial fermentation systems. Graduate and undergraduate students and postdocs trained in this project will be part of a team effort where chemical and molecular genetic approaches take place side-by-side in the same laboratory and often at the same bench. The proposed research will provide cutting-edge HQP training in plant molecular biotechnology and analytical chemistry.