Defining essential processes in plant pathogenesis with Pseudomonas syringae pv. tomato DC3000 disarmed polymutants and a subset of key type III effectors

Abstract

Pseudomonas syringae pv. tomato DC3000 and its derivatives cause disease in tomato, Arabidopsis and Nicotiana benthamiana. The primary virulence factors include a repertoire of 29 effector proteins injected into plant cells by the type III secretion system and the phytotoxin coronatine. The complete repertoire of effector genes and key coronatine biosynthesis genes have been progressively deleted and minimally reassembled to reconstitute basic pathogenic ability in N. benthamiana, and in Arabidopsis plants that have mutations in target genes that mimic effector actions. This approach and molecular studies of effector activities and plant immune system targets have highlighted a small subset of effectors that contribute to essential processes in pathogenesis. Most notably, HopM1 and AvrE1 redundantly promote an aqueous apoplastic environment, and AvrPtoB and AvrPto redundantly block early immune responses, two conditions that are sufficient for substantial bacterial growth in planta. In addition, disarmed DC3000 polymutants have been used to identify the individual effectors responsible for specific activities of the complete repertoire and to more effectively study effector domains, effector interplay and effector actions on host targets. Such work has revealed that AvrPtoB suppresses cell death elicitation in N. benthamiana that is triggered by another effector in the DC3000 repertoire, highlighting an important aspect of effector interplay in native repertoires. Disarmed DC3000 polymutants support the natural delivery of test effectors and infection readouts that more accurately reveal effector functions in key pathogenesis processes, and enable the identification of effectors with similar activities from a broad range of other pathogens that also defeat plants with cytoplasmic effectors.

Suppression of PAMP-triggered immunity (PTI) by effector proteins synthesized by phytopathogens and delivered into cells of infected plant

“…W badaniach laboratoryjnych, szczepem najczęściej wykorzystywanym jest P. syringae pv. tomato DC3000 syntetyzujący zestaw 29 białek efektorowych, które pod względem charakterystyki biochemicznej oraz sposobu ingerowania w funkcjonowanie białek docelowych w funkcjonowanie białek docelowych są najlepiej przebadanymi efektorami [23,30,79]. Poszczególne gatunki i patogenne szczepy bakterii z rodzaju Xanthomonas zakażają około 120 roślin jednoliściennych i 270 dwuliściennych, ale w badaniach białek efektorowych wykorzystuje się kilka szczepów, takich jak: Xoo (X. oryzae pv.…”

Characterization of a Versatile Plant Growth-Promoting Rhizobacterium Pseudomonas mediterranea Strain S58

“…The pathogen P. syringae induced type III secretion system (T3SS)-dependent cell death in non-host plants [45]. Some T3SS effector and Harpin proteins contributed to cell death [45]. An in-depth investigation of the proteomes of P. mediterranea S58 using all T3SS components revealed that it did not contain any T3SS homologs that included effector and Harpin proteins, which are identical to the findings in other P. corrugata and P. mediterranea isolates [39].…”

“…We need to note that strain S58 triggered cell death in tobacco (Figure 8a), which was confirmed by up-regulated expressions of NbHin-1 and NbHsr203J, two typical cell death marker genes (Figure 8c). The pathogen P. syringae induced type III secretion system (T3SS)-dependent cell death in non-host plants [45]. Some T3SS effector and Harpin proteins contributed to cell death [45].…”

Loss of wbpL disrupts O‐polysaccharide synthesis and impairs virulence of plant‐associated Pseudomonas strains

“…Therefore, initial amplification of bacteria within the plant might be delayed until the pathogen can overcome defence responses, e.g. with type III‐secreted effectors like AvrPtoB and AvrPto, and eventually cause disease (Macho and Zipfel, ; Wei and Collmer, ). Additionally, OPS‐deficient mutants could be more sensitive to plant antimicrobial metabolites.…”