title: Clavibacter michiganensis subsp. michiganensis Vatr1 and Vatr2 Transcriptional Regulators Are Required for Virulence in Tomato.
abstract: The plant pathogen Clavibacter michiganensis subsp. michiganensis (Cmm) is a Gram-positive bacterium responsible for wilt and canker disease of tomato. While disease development is well characterized and diagnosed, molecular mechanisms of Cmm virulence are poorly understood. Here, we identified and characterized two Cmm transcriptional regulators, Vatr1 and Vatr2, that are involved in pathogenicity of Cmm. Vatr1 and Vatr2 belong to TetR and MocR families of transcriptional regulators, respectively. Mutations in their corresponding genes caused attenuated virulence, with the Δvatr2 mutant showing a more dramatic effect than Δvatr1. While both mutants grew well in vitro and reached a high titer in planta, they caused reduced wilting and canker development in infected plants compared with the wild-type bacterium. They also led to a reduced expression of the ethylene-synthesizing tomato enzyme ACC-oxidase compared with wild-type Cmm and to reduced ethylene production in the plant. Transcriptomic analysis of wild-type Cmm and the two mutants under infection-mimicking conditions revealed that Vatr1 and Vatr2 regulate expression of virulence factors, membrane and secreted proteins, and signal transducing proteins. A 70% overlap between the sets of genes positively regulated by Vatr1 and Vatr2 suggests that these transcriptional regulators are on the same molecular pathway responsible for Cmm virulence.
authors.affiliation: 1 Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Alon
authors.initials: A
authors.lastname: Savidor
authors.affiliation: 2 Department of Plant Pathology and Weed Research, ARO, the Volcani Center, Bet Dagan 50250, Israel.
authors.forename: Laura
authors.initials: L
authors.lastname: Chalupowicz
authors.affiliation: 1 Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Doron
authors.initials: D
authors.lastname: Teper
authors.affiliation: 1 Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel.|3 Department of Genetechnology/Microbiology, Faculty of Biology, University of Bielefeld, 33501 Bielefeld, Germany.
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Gartemann
authors.affiliation: 3 Department of Genetechnology/Microbiology, Faculty of Biology, University of Bielefeld, 33501 Bielefeld, Germany.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Eichenlaub
authors.affiliation: 2 Department of Plant Pathology and Weed Research, ARO, the Volcani Center, Bet Dagan 50250, Israel.
authors.forename: Shulamit
authors.initials: S
authors.lastname: Manulis-Sasson
authors.affiliation: 1 Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Isaac
authors.initials: I
authors.lastname: Barash
authors.affiliation: 1 Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Guido
authors.initials: G
authors.lastname: Sessa