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  • The EMBO Journal (2007) 26, 1434 - 1443
  • doi:10.1038/sj.emboj.7601575

Published online: 15 February 2007

Pseudomonas syringae pv. tomato hijacks the Arabidopsis abscisic acid signalling pathway to cause disease

Marta de Torres-Zabala1,4, William Truman1,4, Mark H Bennett1, Guillaume Lafforgue1, John W Mansfield1, Pedro Rodriguez Egea2, Laszlo Bögre3 and Murray Grant1,4

  1. Biology Division, Imperial College London, Wye Campus, Wye, UK
  2. Instituto de Biologia Molecular y Celular de Plantas, Universidad Politecnica—CSIC, Camino de Vera, Valencia, Spain
  3. School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK
  4. Present address: School of Biosciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK

Correspondence to:

Murray Grant, School of Biosciences, University of Exeter, Geoffery Pope Building, Stocker Road, Exeter EX4 4QH, UK. Tel.: +44 1392263789; Fax: +44 1392263434; E-mail: M.R.Grant@exeter.ac.uk

Received 18 July 2006; Accepted 4 January 2007

We have found that a major target for effectors secreted by Pseudomonas syringae is the abscisic acid (ABA) signalling pathway. Microarray data identified a prominent group of effector-induced genes that were associated with ABA biosynthesis and also responses to this plant hormone. Genes upregulated by effector delivery share a 42% overlap with ABA-responsive genes and are also components of networks induced by osmotic stress and drought. Strongly induced were NCED3, encoding a key enzyme of ABA biosynthesis, and the abscisic acid insensitive 1 (ABI1) clade of genes encoding protein phosphatases type 2C (PP2Cs) involved in the regulation of ABA signalling. Modification of PP2C expression resulting in ABA insensitivity or hypersensitivity led to restriction or enhanced multiplication of bacteria, respectively. Levels of ABA increased rapidly during bacterial colonisation. Exogenous ABA application enhanced susceptibility, whereas colonisation was reduced in an ABA biosynthetic mutant. Expression of the bacterial effector AvrPtoB in planta modified host ABA signalling. Our data suggest that a major virulence strategy is effector-mediated manipulation of plant hormone homeostasis, which leads to the suppression of defence responses.

  • Keywords:

    • ABA,
    • Arabidopsis thaliana,
    • Pseudomonas syringae,
    • transcriptomics,
    • type III effectors