Functional analysis of Hyaloperonospora arabidopsidis RXLR effectors.
The biotrophic plant pathogen Hyaloperonospora arabidopsidis produces a set of putative effector proteins that contain the conserved RXLR motif. For most of these RXLR proteins the role during infection is unknown. Thirteen RXLR proteins from H. arabidopsidis strain Waco9 were analyzed for sequence similarities and tested for a role in virulence. The thirteen RXLR proteins displayed conserved N-termini and this N-terminal conservation was also found in the 134 predicted RXLR genes from the genome of H. arabidopsidis strain Emoy2. To investigate the effects of single RXLR effector proteins on plant defense responses, thirteen H. arabidopsidis Waco9 RXLR genes were expressed in Arabidopsis thaliana. Subsequently, these plants were screened for altered susceptibility to the oomycetes H. arabidopsidis and Phytophthora capsici, and the bacterial pathogen Pseudomonas syringae. Additionally, the effect of the RXLR proteins on flg22-triggered basal immune responses was assessed. Multifactorial analysis of results collated from all experiments revealed that, except for RXLR20, all RXLR effector proteins tested affected plant immunity. For RXLR9 this was confirmed using a P. syringae ΔCEL-mediated effector delivery system. Together, the results show that many H. arabidopsidis RXLR effectors have small effects on the plant immune response, suggesting that suppression of host immunity by this biotrophic pathogen is likely to be caused by the combined actions of effectors.
Plant-Microbe Interactions, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands; Centre for BioSystems Genomics, Wageningen, The Netherlands.
Michiel J C
MJ
Pel
Plant-Microbe Interactions, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
Paul C A
PC
Wintermans
Plant-Microbe Interactions, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
Adriana
A
Cabral
Ecology and Biodiversity, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
Bjorn J M
BJ
Robroek
Centre for BioSystems Genomics, Wageningen, The Netherlands; Theoretical Biology and Bioinformatics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
Michael F
MF
Seidl
Department of Plant-Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, Germany.
Jaqueline
J
Bautor
Department of Plant-Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, Germany.
Jane E
JE
Parker
Plant-Microbe Interactions, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands; Centre for BioSystems Genomics, Wageningen, The Netherlands.
Guido
G
Van den Ackerveken
Plant-Microbe Interactions, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands; Centre for BioSystems Genomics, Wageningen, The Netherlands.
Corné M J
CM
Pieterse
D017360:Arabidopsis / Q000235:genetics*; D054884:Host-Pathogen Interactions; D009868:Oomycetes / Q000472:pathogenicity*; D010935:Plant Diseases / Q000382:microbiology*; D057865:Plant Immunity / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics*; D014774:Virulence
D010940:Plant Proteins