Open AccessThe gene coding for the Hrp pilus structural protein is required for type III secretion of Hrp and Avr proteins in Pseudomonas syringae pv. tomato
Author(s) -
Wensheng Wei,
Anne E. Plovanich-Jones,
Wen-Ling Deng,
Qingxu Jin,
Alan Collmer,
Hsiou-Chen Huang,
Sheng Yang He
Publication year - 2000
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.040570097
Subject(s) - pilus , secretion , operon , biology , type three secretion system , gene , pseudomonas syringae , mutant , effector , microbiology and biotechnology , gene cluster , transport protein , genetics , virulence , biochemistry
Bacterial surface appendages called pili often are associated with DNA and/or protein transfer between cells. The exact function of pili in the transfer process is not understood and is a matter of considerable debate. The Hrp pilus is assembled by the Hrp type III protein secretion system of Pseudomonas syringae pv. tomato (Pst) strain DC3000. In this study, we show that the hrpA gene, which encodes the major subunit of the Hrp pilus, is required for secretion of putative virulence proteins, such as HrpW and AvrPto. In addition, the hrpA gene is required for full expression of genes that encode regulatory, secretion, and effector proteins of the type III secretion system. hrpA-mediated gene regulation apparently is through effect on the mRNA level of two previously characterized regulatory genes, hrpR and hrpS. Ectopic expression of the hrpRS gene operon restored gene expression, but not protein secretion, in the hrpA mutant. Three single amino acid mutations at the HrpA carboxyl terminus were identified that affect the secretion or regulatory function of the HrpA protein. These results define an essential role of the Hrp pilus structural gene in protein secretion and coordinate regulation of the type III secretion system in Pst DC3000.