CMM-TOMATO INTERACT

Investigating molecular determinants involved in the interaction between Clavibacter michiganensis pv. michiganensis and tomato

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 Obiettivo del progetto (Objective)

'The Gram-positive bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) is the causative agent of wilt and canker disease of tomato that is responsible for heavy damages to agricultural tomato crops worldwide. The molecular mechanisms underlying successful Cmm infection of tomato are poorly understood. Like other plants, tomato possesses an innate immunity system for detection of pathogen-associated molecular patterns (PAMPs), motifs found in conserved molecules of potential invading pathogens. Recognition of PAMPs occurs through transmembrane pattern recognition receptors (PRRs) and results in activation of basal defense responses. Preliminary studies in the Sessa lab indicated that Cmm expresses an extracellular proteinaceous PAMP(s), which is recognized by tomato cells and induces typical basal defenses. Central goal of this proposal is to investigate how tomato plants sense invading Cmm bacteria to activate a first line of defense, and how Cmm overcomes this basal defense responses and develops a successful infection. To this aim, physiological assays will be used to characterize basal defense responses induced by Cmm in tomato plants and suspension-cultured cells. In addition, biochemical and analytical methods will be employed to isolate and identify Cmm proteins with PAMP activity. A proteomics approach based on multi-dimensional protein identification technology (MudPIT) will be used to identify secreted Cmm proteins. Follow up activities will identify among the secreted proteins virulence determinants and possibly PAMP activities. Finally, a screen of Cmm-induced tomato genes based on virus-induced gene silencing (VIGS) techniques will identify tomato proteins involved in recognition of Cmm PAMP(s) and downstream signaling pathways. Together, this investigation will lead to characterization of tomato defense responses activated by Cmm and to the identification of central players in the Cmm-tomato interaction'

Introduzione (Teaser)

Modern agriculture often reverts to molecular studies to understand the interaction between plants and parasites in order to eradicate them. An EU-funded effort is using proteomics to delineate the infection process of tomato plants by the bacterium Clavibacter michiganensis subsp. michiganensis (Cmm).

Descrizione progetto (Article)

Tomato crops worldwide are being threatened by wilt and canker disease caused by the gram-positive Cmm bacterium. The molecular mechanisms underlying successful Cmm infection of tomato are, however, poorly understood.

To study this interaction between the Cmm bacterium and the tomato, the CMM-Tomato Interact project is following a proteomics approach. Scientists have analysed the proteins from tomato plants infected with the wild type and the endophytic Cmm strains and have compared them to the protein levels of control plants.

Thousands of proteins have so far been identified of both host and parasite origin and have helped project partners draw a picture of the infection process. Results indicate that the plant is capable of sensing the invading bacterium and mounts a basal defense response, which most of the times is inadequate to clear the invading parasite.

Project scientists found an important determinant of disease symptom development in tomato, namely the Aminocyclopropanecarboxylate (ACC) oxidase enzyme. ACC is implicated in the biosynthesis of ethylene which is used by plants for fruit ripening.

From the bacterial perspective, data show that the Cmm bacterium is capable of monitoring the plant conditions, transducing signals and secreting hydrolytic enzymes aimed at degrading plant components. Two putative transcription regulators have also been identified that are involved in the Cmm bacterial infectivity.

The identification of such Cmm virulence proteins, combined with the discovery of tomato proteins important for Cmm defense, have the potential to lead to the development of tomato varieties with less susceptibility to Cmm. This will reduce tomato crop losses and boost agriculture-related economies.