Enzymes for the degradation of rhamnogalacturonan I as virulence factors of phytopathogenic bacterium Pectobacterium atrosepticum

Plant pathogenic pectobacteria ( Pectobacterium genus) are well-known all over the world as the causal agents of the cultural plant diseases called soft rots. Rot symptoms are related to the extensive plant tissue maceration due to the production by microorganisms of the plant cell wall degrading enzymes. Most of the pectobacteria-secreted enzymes catalyze the cleavage of homogalacturonan. This polysaccharide, that is a linear homopolymer, consists of galacturonic acid residues and is the most abundant (by mass) pectic polysaccharide of plant cell walls. The knockout of genes of homogalacturonan-degrading enzymes is known to lead to reduced virulence of pectobacteria. In addition, the modification of another pectic compound - rhamnogalacturonan I also occurs in the course of infection process caused by pectobacteria. This compound is a ramified heteropolymer, the backbone of which consists of alternate rhamnose and galacturonic acid residues, and side chains are represented by galactose or arabinose residues...