Biosynthesis of the Antimetabolite 6-Thioguanine in Erwinia amylovora Plays a Key Role in Fire Blight Pathogenesis

摘要

Fire blight is one of the most devastating plant diseases that can eradicate entire orchards. It mainly affects apple and pear trees, among other members of the Rosaceae family. The causative agent of this rapidly spreading disease is the bacterium Erwinia amylovora, historically the first identified bacterial plant pathogen. Its high pathogenicity combined with an almost worldwide spread constitutes serious ecological and economic problems. Thus, deciphering the molecular mechanisms responsible for the success of this bacterium is of utmost importance. The typical symptom of the disease is necrosis of infected tissues with dissemination of the "scorched" phenotype from the infecting point, eventually involving the entire tree. The production of exudates, called ooze, on infected fruits is another characteristic of the disease. Several factors help this pathogen to establish its pathogenicity. An amylovoran exopolysaccharide, which participates in ooze formation, might confer resistance to plant-defensive reactive oxygen species. Effector proteins secreted through a type-three secretion system (T3SS) modulate the plant response such as induction of oxidative burst and manipulation of the jasmonic acid pathway.