Interaction between Plant Hosts and Pathogens

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The interaction between plant hosts and pathogens are complex systems that consist of a vast multitude of components. These components that contribute to these systems are from host as well as pathogenic origin and compete with one another in an attempt to be more successful than the other party. There are many different pathogens that infect plants from all five kingdoms of life and each has a different method of infecting the host. There are several traits that are universal requirements for infection such as gaining entry to the host, overcoming the host’s immune response, replicating effectively within the host and spreading to naïve hosts. Plant cell walls consist of a network of various peptides and polysaccharides. Three categories of polysaccharides exist, namely cellulose, hemicellulose and pectin. Pectin and hemicellulose form the network that the cellulose microfibrils are embedded. The pectin network consists of galacturonic acid (PGA) subunits that are bound by α-1,4-linked glycosidic bonds. This network acts as a primary defence barrier to pathogens that attempt to cross the cell wall to infect the host as well as providing significant structural support. The biosynthesis of pectin is localised to the Golgi vesicles. It has been estimated that 67 different enzymes are required in the biosynthetic pathway of pectin. 384 The reason for the evolution of pectin is mostly unknown and genome comparisons between different plants would provide a clearer insight into its evolution. What is known about the evolution is that the latest development in angiosperms is the presence of the QUA1 ortholog. Plant endoPGs are important for the developmental and remodelling processes during their lifecycles. One of the most prolific en... ... middle of paper ... to produced polygalacturonase-inhibiting proteins (PGIPs) to protect themselves. PGIPs are able to defend themselves against fungal endoPGs, but not against bacterial endoPGs. This has led to the biochemical and computational study of various endoPG enzymes from various sources. EndoPG have many commercial applications that include extraction of fruit juice and vegetable oils, bleaching of paper, the treatment of waste water and as additives in poultry feed. References Oeser, B., Heidrich, P.M., Muller, U., Tudzynski, P., Tenberge, K.B., 2002, Polygalacturonase is a pathogenicity factor in the Claviceps purpurea/rye interaction, Fungal Genetics and Biology, 36: 176–186 Wu, C., Yan, H., Liu, L., Liou, R., 2007, Functional Characterization of a Gene Family Encoding Polygalacturonases in Phytophthora parasitic, Molecular Plant-Microbe Interactions, 21(4): 480-489
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