UBC Theses and Dissertations
Cuticular wax analyses with high spatial and temporal resolution lead to the identification and characterization of novel wax biosynthesis genes in Arabidopsis thaliana Hegebarth, Daniela
Plant cuticles seal above-ground organs against non-stomatal water loss, and therefore are vital for survival on land. Besides providing a transpiration barrier, cuticles have important secondary functions, for example to protect from harmful UV radiation, and to provide a self-cleaning mechanism and mechanical support. Cuticles consist of aliphatic very-long-chain wax compounds (C₂₄ to C₃₈) and a cutin polymer. The diversity of cuticular wax compositions across the plant kingdom but also between different organs and ontogenetic stages is remarkable, yet the regulating mechanisms and function of those chemical differences are largely unknown. In the study presented here, a new approach was used, increasing temporal and spatial resolution and integration of chemical wax analyses with analyses of gene expression patterns of wax biosynthesis genes, using Arabidopsis thaliana as a model organism. The aims of the study were to, first, monitor wax composition and gene expression as a function of leaf development as well as different epidermal cell types and, second, to use this information to identify new wax biosynthesis genes. In the second chapter, high temporal resolution was used to follow the dynamics of wax chemistry and gene expression during development of Arabidopsis thaliana leaves, and I was able to link changes in wax chemistry to differential expression of the elongation enzyme KCS6/CER6. In the third chapter, wax analyses and gene expression data with high spatial resolution were acquired, and I identified differences between Arabidopsis epidermal cell types in wax composition and gene expression. Trichomes had a higher abundance of longer chain waxes (C₃₂ to C₃₈) compared to pavement cells, and the KCS5, KCS8 and KCS16 elongation enzymes were identified as candidates for the elongation of C₃₄₊ waxes. In the fourth chapter, I characterized the Arabidopsis condensing enzyme KCS16 and was able to show that it is functioning on the wax elongation pathway, elongating C₃₄ to C₃₈ acyl-CoA wax precursors, mainly in trichomes but also in pavement cells.
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