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The HopPtoF Locus of Pseudomonas syringae pv. tomato DC3000 Encodes a Type III Chaperone and a Cognate Effector

May 2004 , Volume 17 , Number  5
Pages  447 - 455

Libo Shan , 1 , 4 Hye-sook Oh , 2 Jianfu Chen , 1 Ming Guo , 3 Jianmin Zhou , 1 James R. Alfano , 3 Alan Collmer , 2 Xu Jia , 4 and Xiaoyan Tang 1

1Department of Plant Pathology, Kansas State University, Manhattan 66506-5502 U.S.A.; 2Department of Plant Pathology, Cornell University, Ithaca, NY 14853-4203 U.S.A.; 3Plant Science Initiative and Department of Plant Pathology, University of Nebraska Lincoln 68588-0660 U.S.A.; 4Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China

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Accepted 12 December 2003.

Type III secretion systes are highly conserved among gram-negative plant and animal pathogenic bacteria. Through the type III secretion system, bacteria inject a number of virulence proteins into the host cells. Analysis of the whole genome sequence of Pseudomonas syringae pv. tomato DC3000 strain identified a locus, named HopPtoF, that is homologous to the avirulence gene locus avrPphF in P. syringae pv. phaseolicola. The HopPtoF locus harbors two genes, ShcFPto and HopFPto, that are preceded by a single hrp box promoter. We present evidence here to show that ShcFPto and HopFPto encode a type III chaperone and a cognate effector, respectively. ShcFPto interacts with and stabilizes the HopFPto protein in the bacterial cell. Translation of HopFPto starts at a rare initiation codon ATA that limits the synthesis of the HopFPto protein to a low level in bacterial cells.

© 2004 The American Phytopathological Society