plant signal salicylic acid shuts down expression of the vir regulon and activates quormone-quenching genes in Agrobacterium

Agrobacterium tumefaciens is capable of transferring and integrating an oncogenic T-DNA (transferred DNA) from its tumor-inducing (Ti) plasmid into dicotyledonous plants. This transfer requires that the virulence genes (vir regulon) be induced by plant signals such as acetosyringone in an acidic env...

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Published in:Proceedings of the National Academy of Sciences - PNAS 2007-07, Vol.104 (28), p.11790-11795
Main Authors: Yuan, Ze-Chun, Edlind, Merritt P, Liu, Pu, Saenkham, Panatda, Banta, Lois M, Wise, Arlene A, Ronzone, Erik, Binns, Andrew N, Kerr, Kathleen, Nester, Eugene W
Format: Article
Language:English
Subjects:
4-Butyrolactone - analogs & derivatives
4-Butyrolactone - metabolism
4-Butyrolactone - physiology
Acids
Agrobacterium
Agrobacterium tumefaciens
Arabidopsis - genetics
Arabidopsis - metabolism
Arabidopsis - microbiology
Arabidopsis thaliana
Bacteria
Bacteriology
Biological Sciences
crown galls
Deoxyribonucleic acid
disease resistance
DNA
Down-Regulation - genetics
gene expression regulation
Gene Expression Regulation, Bacterial - physiology
Gene Expression Regulation, Plant - physiology
Genes
host-pathogen relationships
Infections
lactonase
lactones
metabolism
microbial genetics
N-acylhomoserine lactone
Operons
Plant tumor inducing plasmids
plant tumors
Plants
Plasmids
protein kinases
Regulon
Regulon - genetics
resistance mechanisms
Rhizobium - genetics
Rhizobium - metabolism
Rhizobium - pathogenicity
salicylic acid
Salicylic Acid - metabolism
Salicylic Acid - pharmacology
Signal Transduction - genetics
Signal Transduction - physiology
Tumors
vir genes
VirA kinase
Virulence - genetics
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Summary:Agrobacterium tumefaciens is capable of transferring and integrating an oncogenic T-DNA (transferred DNA) from its tumor-inducing (Ti) plasmid into dicotyledonous plants. This transfer requires that the virulence genes (vir regulon) be induced by plant signals such as acetosyringone in an acidic environment. Salicylic acid (SA) is a key signal molecule in regulating plant defense against pathogens. However, how SA influences Agrobacterium and its interactions with plants is poorly understood. Here we show that SA can directly shut down the expression of the vir regulon. SA specifically inhibited the expression of the Agrobacterium virA/G two-component regulatory system that tightly controls the expression of the vir regulon including the repABC operon on the Ti plasmid. We provide evidence suggesting that SA attenuates the function of the VirA kinase domain. Independent of its effect on the vir regulon, SA up-regulated the attKLM operon, which functions in degrading the bacterial quormone N-acylhomoserine lactone. Plants defective in SA accumulation were more susceptible to Agrobacterium infection, whereas plants overproducing SA were relatively recalcitrant to tumor formation. Our results illustrate that SA, besides its well known function in regulating plant defense, can also interfere directly with several aspects of the Agrobacterium infection process.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0704866104