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Characterization of cell wall in transgenic aspen with modified xylan acetylation
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
2015 (Engelska)Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
Abstract [en]

ABSTRACT

Mature plant cells are enclosed by inflexible wall made up of cellulose microfibrils, pectins, hemicelluloses and in some cases lignin. This cell wall provides the structure and the defense for plant cells. In secondary cell walls of dicotyledons, major hemicellulose is xylan consisting of β-(1, 4)-linked xylose units. Xylan is synthesized in Golgi apparatus by several enzymes activities. REDUCED WALL ACETYLATION (RWA) genes are involved in xylan acetylation. These genes were downregulated in hybrid aspen in order to reduce xylan acetylation activity during its biosynthesis. In addition, acetyl xylan esterase (FC2) from the fungus Aspergillus niger was expressed in hybrid aspen to modify xylan acetylation post-synthetically. In this work, I have studied effects of these modifications on wood cell wall composition.

The cell wall components were sequentially extracted by using the small scale method and the weight of extractives, lignin, hemicelluloses and celluloses per weight of dry wood were determined. In addition, the Updegraff cellulose, Klason lignin contents per weight of extractive free wood were determined and monosugar compositions of non-cellulosic components were analyzed by methanolysis and Trimethylsilyl derivatisation (TMS). 

I have found that content of cellulose determined by sequential extraction method was significantly increased in all constructs as compared to the wild type. Reduction of lignin (as determined by sequential extraction) was found in DFC2 construct and RWA RNAi 35S-AB and CD constructs. Furthermore, RWA RNAi 35S-CD and RWA RNAi WP-ABCD constructs showed decreased hemicellulose as compared to the wild type. Moreover, DFC2 constructs exhibited decrease in non-cellulosic sugars hydrolyzed during TMS. FC2 expressing lines showed a reduction in xylose which is the main building block of xylan. In contrast, glucose and galactose contents were increased. Inhibition of expression of all RWA genes (WP-ABCD) caused similar changes.

Considering all the data I conclude that, reduced acetylation of xylan can affect extractability, biosynthesis or modification of polysaccharides and lignin in cell wall.

Keywords: Cellulose microfibrils; pectins; hemicellulose; lignin, xylan; secondary wall; aspen; xylan biosynthesis; biosynthesis of polysaccharides. 

Ort, förlag, år, upplaga, sidor
2015.
Nationell ämneskategori
Biokemi och molekylärbiologi
Identifikatorer
URN: urn:nbn:se:umu:diva-101316OAI: oai:DiVA.org:umu-101316DiVA, id: diva2:798487
Externt samarbete
Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SLU
Utbildningsprogram
Masterprogrammet i växt- och skogsbioteknik
Handledare
Examinatorer
Tillgänglig från: 2015-03-27 Skapad: 2015-03-26 Senast uppdaterad: 2015-03-27Bibliografiskt granskad

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