The Type III Secreted Effector DspE Is Required Early in Solanum tuberosum Leaf Infection by Pectobacterium carotovorum to Cause Cell Death, and Requires Wx(3–6)D/E Motifs

Abstract

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.

Show me your secret(ed) weapons: a multifaceted approach reveals a wide arsenal of type III‐secreted effectors in the cucurbit pathogenic bacterium Acidovorax citrulli and novel effectors in the Acidovorax genus

“…The main objective of this study was to significantly advance the current knowledge about the arsenal of T3Es of A. citrulli . Among well‐investigated plant pathogenic bacteria, the pools of T3Es vary from only few effectors in phytopathogenic bacteria from the Enterobacteriaceae family (Hogan et al , ; Nissinen et al , ) to approximately 20–40 in most strains of P. syringae and Xanthomonas spp. (Büttner and Bonas, ; Chang et al , ; Kvitko et al , ; O'Brien et al , ; Schechter et al , ; Teper et al , ; White et al , ) and an average of over 75 in R. solanacearum isolates (Deslandes and Genin, ; Peeters et al , ).…”

The Pseudomonas viridiflava phylogroups in the P. syringae species complex are characterized by genetic variability and phenotypic plasticity of pathogenicity‐related traits

“…Our results reflect findings from the potato soft rot pathogen Pectobacterium carotovorum subsp. carotovorum in which the only effector secreted during pathogenicity is DspE, a protein similar to AvrE (Hogan et al ., ). We speculate that the soft rot P. viridiflava and P. carotovorum strains do not require a wide range of T3SS genes to suppress host immune responses since AvrE, likely in conjunction with pectolytic enzymes, is likely to be sufficient to induce disease symptoms.…”

Pseudomonas syringae Effector Avirulence Protein E Localizes to the Host Plasma Membrane and Down-Regulates the Expression of the NONRACE-SPECIFIC DISEASE RESISTANCE1/HARPIN-INDUCED1-LIKE13 Gene Required for Antibacterial Immunity in Arabidopsis

“…All AvrE family effectors examined, including AvrE from Pst DC3000, Water-Soaking E (WtsE) from Pantoea stewartii, Disease-specific protein A (DspA)/E from Erwinia amylovora, and DspE from Pectobacterium carotovorum, are strong inducers of water soaking and/or cell death when expressed in host or nonhost plants (Frederick et al, 2001;Boureau et al, 2006;Ham et al, 2006Ham et al, , 2008Ham et al, , 2009Degrave et al, 2008;Kim et al, 2011;Hogan et al, 2013). Conversely, deletion of avrE family genes delays or abolishes this ability (Bogdanove et al, 1998;Frederick et al, 2001;Badel et al, 2006;Ham et al, 2006).…”