UBC Theses and Dissertations
Investigating the biosynthesis of cuticular alkanes in Arabidopsis thaliana : Characterization of SCD2 and chemical analysis of double CER mutant waxes Skvortsova, Mariya
The plant cuticle is a hydrophobic layer that seals the surface of primary aerial organs of terrestrial plants and serves in protecting the tissues from abiotic and biotic stresses. Lipids are synthesized in the plastid and in the endoplasmic reticulum (ER) of epidermal cells for eventual export and deposition on the surface. Great progress has been made by genetic studies in the model plant Arabidopsis thaliana in elucidating fatty acid elongation, but knowledge of alkane biosynthesis is still scarce. The current work was focused on expanding our current understanding of alkane biosynthesis in Arabidopsis thaliana. A recent discovery of Susceptible to Coronatine-Deficient Pst DC3118-2 (SCD2) whose mutant has a leaf-specific increase in aldehydes and a decrease in alkanes suggests that SCD2 has a role in converting aldehydes to alkanes. In this thesis, further characterization of SCD2 revealed that alkanes are decreased in two mutant lines, the wax of mutants was restored by transgene complementation with the native gene, the transcript is abundant in leaves, and the promoter is active in the phloem of vasculature. Finally, the protein localized to the ER, consistent with its role in wax biosynthesis. This work provided evidence for yet another gene whose product is involved in formation of cuticular alkanes in Arabidopsis thaliana. Double mutants were generated to further study wax biosynthesis in both stems and leaves. The cer1cer3 mutant had greatly reduced total stem and leaf wax amounts compared to wild-type, as well as a substantial reduction of alkanes. It has an increase in C30 primary alcohol levels like the cer3 parent, indicating epistasis. This suggests that CER3 precedes CER1 in alkane formation. Furthermore, it is severely male-sterile with a reduction in epicuticular wax crystals. Wax biosynthesis is similar in stems and leaves of cer1cer3, cer1cer4 and cer3cer4. The cer1cer3 will be an important tool to test domain functionality of CER1 and CER3 and may shed more light on the mechanisms of alkane formation in Arabidopsis thaliana.
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