The plant cell wall presents the first line of defence against invading pathogens and serves as a physical barrier hindering pathogen progression in the host tissues. This chapter provides an overview of the recent progress that has advanced our understanding of the mechanisms of biosynthesis and biological role of arabinan, with the main focus of the role of arabinan in plant-microbe interaction. Arabinan modifying enzymes show the similar overall pattern of transcript profiles during development. In addition, the transcript levels of AtBXL1 and AtBXL2 exhibit a circadian oscillation. Evidence based on immunohistochemical analysis indicates that the structure and distribution of arabinan also vary considerably across plant tissues during development. Arabinan has been implicated to play roles in cell-to-cell adhesion. Pollen grains were collapsed in mature anthers during the release of microspores from microsporocytes and degeneration of tapetum. Cell wall polysaccharides are well documented to influence the outcome of host-pathogen interactions.