A family of bacterial cysteine protease type III effectors utilizes acylation-dependent and -independent strategies to localize to plasma membranes.
Bacterial phytopathogens employ a type III secretion system to deliver effector proteins into the plant cell to suppress defense pathways; however, the molecular mechanisms and subcellular localization strategies that drive effector function largely remain a mystery. Here, we demonstrate that the plant plasma membrane is the primary site for subcellular localization of the Pseudomonas syringae effector AvrPphB and five additional cysteine protease family members. AvrPphB and two AvrPphB-like effectors, ORF4 and NopT, autoproteolytically process following delivery into the plant cell to expose embedded sites for fatty acylation. Host-dependent lipidation of these three effectors directs plasma membrane localization and is required for the avirulence activity of AvrPphB. Surprisingly, the AvrPphB-like effectors RipT, HopC1, and HopN1 utilize an acylation-independent mechanism to localize to the cellular plasma membrane. Although some AvrPphB-like effectors employ acylation-independent localization strategies, others hijack the eukaryotic lipidation machinery to ensure plasma membrane localization, illustrating the diverse tactics employed by type III effectors to target specific subcellular compartments.
Departments of Pharmacology, Cellular and Molecular Medicine, and Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0721, USA.
Robert H
RH
Dowen
James L
JL
Engel
Feng
F
Shao
Joseph R
JR
Ecker
Jack E
JE
Dixon
D000215:Acylation; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology*; D003001:Cloning, Molecular; D003360:Cosmids; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005822:Genetic Vectors; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D044224:Pseudomonas syringae / Q000201:enzymology*; D012231:Rhizobium / Q000201:enzymology; D012241:Rhodopseudomonas / Q000201:enzymology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D003546:Cysteine Endopeptidases