title: Waterproofing in Arabidopsis: Following Phenolics and Lipids In situ by Confocal Raman Microscopy.
abstract: Waterproofing of the aerial organs of plants imposed a big evolutionary step during the colonization of the terrestrial environment. The main plant polymers responsible of water repelling are lipids and lignin, which play also important roles in the protection against biotic/abiotic stresses, regulation of flux of gases and solutes, and mechanical stability against negative pressure, among others. While the lipids, non-polymerized cuticular waxes together with the polymerized cutin, protect the outer surface, lignin is confined to the secondary cell wall within mechanical important tissues. In the present work a micro cross-section of the stem of Arabidopsis thaliana was used to track in situ the distribution of these non-carbohydrate polymers by Confocal Raman Microscopy. Raman hyperspectral imaging gives a molecular fingerprint of the native waterproofing tissues and cells with diffraction limited spatial resolution (~300 nm) at relatively high speed and without any tedious sample preparation. Lipids and lignified tissues as well as their effect on water content was directly visualized by integrating the 1299, 1600, and 3400 cm(-1) band, respectively. For detailed insights into compositional changes of these polymers vertex component analysis was performed on selected sample positions. Changes have been elucidated in the composition of lignin within the lignified tissues and between interfascicular fibers and xylem vessels. Hydrophobizing changes were revealed from the epidermal layer to the cuticle as well as a change in the aromatic composition within the cuticle of trichomes. To verify Raman signatures of different waterproofing polymers additionally Raman spectra of the cuticle and cutin monomer from tomato (Solanum lycopersicum) as well as aromatic model polymers (milled wood lignin and dehydrogenation polymer of coniferyl alcohol) and phenolic acids were acquired.
authors.affiliation: Department of Material Sciences and Process Engineering, University of Natural Resources and Life Sciences Vienna, Austria.
authors.forename: Batirtze
authors.initials: B
authors.lastname: Prats Mateu
authors.affiliation: Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences Vienna, Austria.
authors.forename: Marie Theres
authors.initials: MT
authors.lastname: Hauser
authors.affiliation: Department of Molecular Biology and Biochemistry, University of Malaga Malaga, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Heredia
authors.affiliation: Department of Material Sciences and Process Engineering, University of Natural Resources and Life SciencesVienna, Austria; Institute for Building Materials, Eidgenössische Technische Hochschule ZürichZürich, Switzerland; Applied Wood Research Laboratory, Empa-Swiss Federal Laboratories for Material Testing and ResearchDübendorf, Switzerland.
authors.forename: Notburga
authors.initials: N
authors.lastname: Gierlinger
keywords: Raman; cuticle; cutin; lignin; secondary cell wall; trichomes; wax