Enzymatic systems for carbohydrate utilization and biosynthesis in Xanthomonas and their role in pathogenesis and tissue specificity

Xanthomonas plant pathogens can infect hundreds of agricultural plants. These bacte-ria exploit sophisticated molecular strategies based on multiple secretion systems and their associated virulence factors to overcome the plant defenses, including the physi-cal barrier imposed by the plant cell walls and the innate immune system. Xanthomon-ads are equipped with a broad and diverse repertoire of Carbohydrate-Active enZymes (CAZymes), which besides enabling the utilization of complex plant carbohydrates as car-bon and energy source, can also play pivotal roles in virulence and bacterial lifestyle in the host. CAZymes in xanthomonads are often organized in multienzymatic systems simi-lar to the Polysaccharide Utilization Loci (PUL) from Bacteroidetes known as CUT systems (from Carbohydrate Utilization systems associated with TonB-dependent transporters). Xan-thomonas bacteria are also recognized to synthesize distinct exopolysaccharides including xanthan gum and untapped exopolysaccharides associated with biofilm formation. Here, we summarize the current knowledge on the multifaceted roles of CAZymes in xanthomonads, connecting their function with pathogenicity and tissue specificity.

Automated summary

Xanthomonas plant pathogens have developed sophisticated strategies to overcome plant defenses using multiple secretion systems and virulence factors. They possess a diverse repertoire of Carbohydrate-Active enzymes (CAZymes) that not only enable them to utilize complex plant carbohydrates, but also play important roles in virulence and bacterial lifestyle. These CAZymes are often organized in multienzymatic systems similar to Bacteroidetes' Polysaccharide Utilization Loci (PUL) known as CUT systems. Xanthomonas bacteria also produce distinct exopolysaccharides, such as xanthan gum, associated with biofilm formation.