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Investigating the regulatory mechanisms of cuticular wax biosynthesis in Arabidopsis thaliana Liu, Shuang

Abstract

As an integral part of plant cuticle, cuticular wax covers the primary aerial organs of plants and provides protection against desiccation and environmental stresses. It has been shown that cuticular wax biosynthesis is synchronized with the surface area expansion during plant development and is associated with plant responses to biotic and abiotic stresses. As the plant-environment interface, cuticular wax deposition is tightly regulated. The major goal of my Ph.D. study was to investigate the regulatory mechanisms that control cuticular wax accumulation during development and/or in response to environmental cues by identifying and characterizing factors that are involved in this process. In this thesis, I investigated two types of regulation of wax accumulation. Firstly, studies of the RING-type E3 ligase U37 demonstrated that U37-mediated ubiquitination is involved in the regulation of wax biosynthesis (Chapter 3). U37 ubiquitinates wax biosynthetic enzyme ECERIFERUM1 (CER1), and possibly also ECERIFERUM3 (CER3), and targets them for degradation via the 26S proteasome. Based on the U37 expression profile, I proposed that U37 might have a major function in turning off wax biosynthesis in fully developed leaves. Secondly, the identification and partial characterization of novel transcription factors that bind to the CER3 promoter revealed that CER3 is an important regulatory determinant in transcriptional regulation of cuticular wax biosynthesis (Chapter 4). Four transcription factors, MYB30, WIP5, AHL29 and AHL23, have been identified that likely control cuticular wax deposition by regulating CER3 gene expression.

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