The plant cell wall is a dynamic structure and it is involved in regulating a number of physiological features of plants such as physical strength, growth, cell differentiation, intercellular communication, water movement and defense responses.

Pectins constitute a major class of plant cell wall polysaccharides and consist of backbones rich in galacturonic acids, which are decorated with a range of functional groups including acetyl esters and arabinan sidechains. Although much effort has been made to uncover biological functions of pectins in plants and remarkable progresses have taken place, many aspects remain elusive.

Studies described in this thesis aimed at gaining new insights into the biological roles of pectin acetylation and arabinosylation in the model plant Arabidopsis thaliana.

The thesis consists of four chapters: physiological characterization of cell wall mutants affected in cell wall acetylation (Chapter 2), identification of a candidate gene required for acetylation of pectin (Chapter 3), screening of pectin mutants for susceptibility to the nectrotrophic fungal pathogen Botrytis cinerea (Chapter 4), and identification and functional characterization of an arabinan-degrading enzyme secreted by B. cinerea during infection of plants (Chapter 5).

The results described resulted in valuable new knowledge regarding the role of pectin acetylation and arabinosylation in the model plant Arabidopsis thaliana documented in three published research papers, one manuscript and one accepted book chapter.