Dokument: Advancing the Understanding of Xyloglucan Biosynthesis and Function in Plants through Diverse Genetic Engineering Approaches

Titel:	Advancing the Understanding of Xyloglucan Biosynthesis and Function in Plants through Diverse Genetic Engineering Approaches
URL für Lesezeichen:	https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=71879
URN (NBN):	urn:nbn:de:hbz:061-20260120-124452-0
Kollektion:	Dissertationen
Sprache:	Englisch
Dokumententyp:	Wissenschaftliche Abschlussarbeiten » Dissertation
Medientyp:	Text
Autor:	Immelmann, Ronja Catharina [Autor]
Dateien:	[Dateien anzeigen] Adobe PDF [Details] 13,50 MB in einer Datei [ZIP-Datei erzeugen] Dateien vom 14.01.2026 / geändert 14.01.2026
Beitragende:	Pauly, Markus [Gutachter] Prof. Dr. Axmann, Ilka Maria [Gutachter]
Dewey Dezimal-Klassifikation:	500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie
Beschreibung:	Advancing the Understanding of Xyloglucan Biosynthesis and Function in Plants through Diverse Genetic Engineering Approaches Ronja Catharina Immelmann Plant cells are enclosed by a complex cell wall primarily composed of the polysaccharides cellulose, hemicellulose and pectin. Xyloglucan (XyG) is the predominant hemicellulose in the primary cell walls of dicot plants and is characterized by a glucan backbone substituted with xylosyl residues. These xylose residues are often further decorated with glycosyl and non-glycosyl residues, which vary in a species- and tissue-specific manner. While several enzymes involved in XyG biosynthesis have been identified, others remain to be discovered, and the functions of many known enzymes require further characterization. In this thesis, previously uncharacterized XyG-related glycosyltransferases were identified and functionally analysed. Focus was placed on XyG:xylosyltransferases (XXTs) from Hymenaea courbaril, a species that produces highly xylosylated XyG. Three Hymenaea XXT homologs were identified and one of these induced hyperxylosylation in an Arabidopsis thaliana complementation approach. The resulting XyG structures were analysed using mass spectrometry, providing novel insights into the functional diversity within the XXT enzyme family. Additionally, a xylosyltransferase from blueberry responsible for the synthesis of a unique xylosylated sidechain (“U” sidechain) was identified and characterized. Functional complementation in Arabidopsis followed by mass spectrometry, glycosidic linkage analysis and NMR spectroscopy of XyG oligosaccharides confirmed its role. A synthetic biology approach was employed using Pichia pastoris to reconstitute XyG biosynthesis and determine the enzymatic components required to generate a plant-like xylosylated glucan polymer. Building on the prior successful synthesis of a glucan backbone in Pichia, efforts were focused on enhancing xylosylation by co-expressing additional XyG biosynthetic enzymes and modifying the nucleotide sugar biosynthesis pathways required for XyG synthesis. Given the evolutionary interest in the origin of XyG biosynthesis, Pichia was also utilized to assess the functionality of putative XyG biosynthetic enzymes from various algal species. This analysis revealed that some charophycean green algae, which are evolutionarily close to land plants, possess functional XyG biosynthesis enzymes. Although XyG deficiency in Arabidopsis results in only mild and tissue-specific phenotypes, it has been proposed that functional redundancy with other wall components may compensate for its absence. To test this hypothesis, Arabidopsis lines lacking multiple wall polymers were generated and analysed, providing insight into potential compensatory mechanisms among cell wall components.
Lizenz:	Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz
Fachbereich / Einrichtung:	Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie
Dokument erstellt am:	20.01.2026
Dateien geändert am:	20.01.2026
Promotionsantrag am:	06.08.2025
Datum der Promotion:	17.12.2025