A protein phosphatase 2C, responsive to the bacterial effector AvrRpm1 but not to the AvrB effector, regulates defense responses in Arabidopsis.
Using a proteomics approach, a PP2C-type phosphatase (renamed PIA1, for PP2C induced by AvrRpm1) was identified that accumulates following infection by Pseudomonas syringae expressing the type III effector AvrRpm1, and subsequent activation of the corresponding plant NB-LRR disease resistance protein RPM1. No accumulation of PIA1 protein was seen following infection with P. syringae expressing AvrB, another type III effector that also activates RPM1, although PIA transcripts were observed. Accordingly, mutation of PIA1 resulted in enhanced RPM1 function in response to P. syringae pathover tomato (Pto) DC3000 (avrRpm1) but not to Pto DC3000 (avrB). Thus, PIA1 is a protein marker that distinguishes AvrRpm1- and AvrB-dependent activation of RPM1. AvrRpm1-induced expression of the pathogenesis-related genes PR1, PR2 and PR3, and salicylic acid accumulation were reduced in two pia1 mutants. By contrast, expression of other defense-related genes, including PR5 and PDF1.2 (plant defensin), was elevated in unchallenged pia1 mutants. Hence, PIA1 is required for AvrRpm1-induced responses, and confers dual (both positive and negative) regulation of defense gene expression.
Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany.
Ivy
I
Widjaja
Ines
I
Lassowskat
Gerit
G
Bethke
Lennart
L
Eschen-Lippold
Hoang-Hoa
HH
Long
Kai
K
Naumann
Jeffery L
JL
Dangl
Dierk
D
Scheel
Justin
J
Lee
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D015180:Electrophoresis, Gel, Two-Dimensional; D054884:Host-Pathogen Interactions; D007113:Immunity, Innate / Q000235:genetics; D013058:Mass Spectrometry; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D030821:Plants, Genetically Modified; D000071636:Protein Phosphatase 2C; D040901:Proteomics; D044224:Pseudomonas syringae / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction
D029681:Arabidopsis Proteins; C100931:AvrB protein, Pseudomonas syringae; C502082:AvrRpm1 protein, Pseudomonas syringae; D001426:Bacterial Proteins; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C