Structural and functional analysis of the type III secretion system from Pseudomonas fluorescens Q8r1-96.
Pseudomonas fluorescens Q8r1-96 represents a group of rhizosphere strains responsible for the suppressiveness of agricultural soils to take-all disease of wheat. It produces the antibiotic 2,4-diacetylphloroglucinol and aggressively colonizes the roots of cereal crops. In this study, we analyzed the genome of Q8r1-96 and identified a type III protein secretion system (T3SS) gene cluster that has overall organization similar to that of the T3SS gene cluster of the plant pathogen Pseudomonas syringae. We also screened a collection of 30 closely related P. fluorescens strains and detected the T3SS genes in all but one of them. The Q8r1-96 genome contained ropAA and ropM type III effector genes, which are orthologs of the P. syringae effector genes hopAA1-1 and hopM1, as well as a novel type III effector gene designated ropB. These type III effector genes encoded proteins that were secreted in culture and injected into plant cells by both P. syringae and Q8r1-96 T3SSs. The Q8r1-96 T3SS was expressed in the rhizosphere, but mutants lacking a functional T3SS were not altered in their rhizosphere competence. The Q8r1-96 type III effectors RopAA, RopB, and RopM were capable of suppressing the hypersensitive response and production of reactive oxygen species, two plant immune responses.
Mavrodi
Dmitri V
DV
Department of Plant Pathology, Washington State University, Pullman, Washington 99164-6430, USA. thomashow@wsu.edu
Joe
Anna
A
Mavrodi
Olga V
OV
Hassan
Karl A
KA
Weller
David M
DM
Paulsen
Ian T
IT
Loper
Joyce E
JE
Alfano
James R
JR
Thomashow
Linda S
LS
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002876:Chromosomes, Bacterial; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D009154:Mutation; D017856:Phosphotransferases (Phosphate Group Acceptor); D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology / Q000517:prevention & control; D018517:Plant Roots / Q000382:microbiology; D011551:Pseudomonas fluorescens / Q000145:classification* / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D012988:Soil Microbiology; D014908:Triticum / Q000382:microbiology
D001426:Bacterial Proteins; D017856:Phosphotransferases (Phosphate Group Acceptor); C059169:polyphosphate AMP phosphotransferase