title: Bacterial and plant signal integration via D3-type cyclins enhances symptom development in the Arabidopsis-Rhodococcus fascians interaction.
abstract: The phytopathogenic actinomycete Rhodococcus fascians drives its host to form a nutrient-rich niche by secreting a mixture of cytokinins that triggers plant cell division and shoot formation. The discrepancy between the relatively low amount of secreted cytokinins and the severe impact of R. fascians infection on plant development has puzzled researchers for a long time. Polyamine and transcript profiling of wild-type and cytokinin receptor mutant plants revealed that the bacterial cytokinins directly stimulated the biosynthesis of plant putrescine by activating arginine decarboxylase expression. Pharmacological experiments showed that the increased levels of putrescine contributed to the severity of the symptoms. Thus, putrescine functions as a secondary signal that impinges on the cytokinin-activated pathway, amplifying the hormone-induced changes that lead to the formation of a leafy gall. Exogenous putrescine and treatment with polyamine biosynthesis inhibitors combined with transcript and polyamine analyses of wild-type and mutant plants indicated that the direct target of both the bacterial cytokinins and plant putrescine was the expression of D3-type cyclins. Hence, the activated d-type cyclin/retinoblastoma/E2F transcription factor pathway integrates both external and internal hormonal signals, stimulating mitotic cell divisions and inducing pathological plant organogenesis.
authors: Department of Plant Biotechnology and Genetics, Ghent University, 9052 Ghent, Belgium.
authors: Elisabeth
authors: E
authors: Stes
authors: Stefania
authors: S
authors: Biondi
authors: Marcelle
authors: M
authors: Holsters
authors: Danny
authors: D
authors: Vereecke
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000494:pharmacology; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D054884:Host-Pathogen Interactions / Q000187:drug effects; D007700:Kinetics; D008954:Models, Biological; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000166:cytology / Q000187:drug effects / Q000382:microbiology; D011700:Putrescine / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012240:Rhodococcus / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D029681:Arabidopsis Proteins; C496944:CycD3 protein, Arabidopsis; D016213:Cyclins; D003583:Cytokinins; D012333:RNA, Messenger; C030965:alpha-(difluoromethyl)arginine; D001120:Arginine; D002262:Carboxy-Lyases; C019722:arginine decarboxylase; D011700:Putrescine