RESUMO
Pectobacterium species are enterobacterial plant-pathogens that cause soft rot disease in diverse plant species. Unlike hemi-biotrophic plant pathogenic bacteria, the type III secretion system (T3SS) of Pectobacterium carotovorum subsp. carotovorum (P. carotovorum) appears to secrete only one effector protein, DspE. Previously, we found that the T3SS regulator HrpL and the effector DspE are required for P. carotovorum pathogenesis on leaves. Here, we identified genes up-regulated by HrpL, visualized expression of dspE in leaves, and established that DspE causes host cell death. DspE required its full length and WxxxE-like motifs, which are characteristic of the AvrE-family effectors, for host cell death. We also examined expression in plant leaves and showed that hrpL is required for the expression of dspE and hrpN, and that the loss of a functional T3SS had unexpected effects on expression of other genes during leaf infection. These data support a model where P. carotovorum uses the T3SS early in leaf infection to initiate pathogenesis through elicitation of DspE-mediated host cell death.
Assuntos
Proteínas de Bactérias/genética , Cromossomos Bacterianos/química , Regulação Bacteriana da Expressão Gênica , Interações Hospedeiro-Patógeno , Pectobacterium carotovorum/genética , Solanum tuberosum/microbiologia , Fatores de Virulência/genética , Agrobacterium tumefaciens/genética , Agrobacterium tumefaciens/metabolismo , Motivos de Aminoácidos , Arabidopsis/microbiologia , Proteínas de Bactérias/metabolismo , Morte Celular , Ilhas Genômicas , Dados de Sequência Molecular , Pectobacterium carotovorum/metabolismo , Pectobacterium carotovorum/patogenicidade , Células Vegetais/metabolismo , Células Vegetais/microbiologia , Células Vegetais/patologia , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , Alinhamento de Sequência , Fatores de Tempo , Nicotiana/microbiologia , Fatores de Virulência/metabolismoRESUMO
Pectobacterium species are necrotrophic bacterial pathogens that cause soft rot diseases in potatoes and several other crops worldwide. Gene expression data identified Pectobacterium carotovorum subsp. carotovorum budB, which encodes the α-acetolactate synthase enzyme in the 2,3-butanediol pathway, as more highly expressed in potato tubers than potato stems. This pathway is of interest because volatiles produced by the 2,3-butanediol pathway have been shown to act as plant growth promoting molecules, insect attractants, and, in other bacterial species, affect virulence and fitness. Disruption of the 2,3-butanediol pathway reduced virulence of P. c. subsp. carotovorum WPP14 on potato tubers and impaired alkalinization of growth medium and potato tubers under anaerobic conditions. Alkalinization of the milieu via this pathway may aid in plant cell maceration since Pectobacterium pectate lyases are most active at alkaline pH.