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The type III effector RipB from Ralstonia solanacearum RS1000 acts as a major avirulence factor in Nicotiana benthamiana and other Nicotiana species.

ABSTRACT: Ralstonia solanacearum is the causal agent of bacterial wilt in solanaceous crops. This pathogen injects approximately 70 effector proteins into plant cells via the Hrp type III secretion system in an early stage of infection. To identify an as-yet-unidentified avirulence factor possessed by the Japanese tobacco-avirulent strain RS1000, we transiently expressed RS1000 effectors in Nicotiana benthamiana leaves and monitored their ability to induce effector-triggered immunity (ETI). The expression of RipB strongly induced the production of reactive oxygen species and the expressions of defence-related genes in N. benthamiana. The ripB mutant of RS1002, a nalixidic acid-resistant derivative of RS1000, caused wilting symptoms in N. benthamiana. A pathogenicity test using R. solanacearum mutants revealed that the two already known avirulence factors RipP1 and RipAA contribute in part to the avirulence of RS1002 in N. benthamiana. The Japanese tobacco-virulent strain BK1002 contains mutations in ripB and expresses a C-terminal-truncated RipB that lost the ability to induce ETI in N. benthamiana, indicating a fine-tuning of the pathogen effector repertoire to evade plant recognition. RipB shares homology with Xanthomonas XopQ, which is recognized by the resistance protein Roq1. The RipB-induced resistance against R. solanacearum was abolished in Roq1-silenced plants. These findings indicate that RipB acts as a major avirulence factor in N. benthamiana and that Roq1 is involved in the recognition of RipB.

SUBMITTER: Nakano M

PROVIDER: S-EPMC6715614 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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The type III effector RipB from Ralstonia solanacearum RS1000 acts as a major avirulence factor in Nicotiana benthamiana and other Nicotiana species.

Nakano Masahito M Mukaihara Takafumi T

Molecular plant pathology 20190620 9

Ralstonia solanacearum is the causal agent of bacterial wilt in solanaceous crops. This pathogen injects approximately 70 effector proteins into plant cells via the Hrp type III secretion system in an early stage of infection. To identify an as-yet-unidentified avirulence factor possessed by the Japanese tobacco-avirulent strain RS1000, we transiently expressed RS1000 effectors in Nicotiana benthamiana leaves and monitored their ability to induce effector-triggered immunity (ETI). The expression ...[more]

PMID: 31218811

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Project description:The plant pathogen Ralstonia solanacearum possesses two genes encoding a trehalose-6-phosphate synthase (TPS), an enzyme of the trehalose biosynthetic pathway. One of these genes, named ripTPS, was found to encode a protein with an additional N-terminal domain which directs its translocation into host plant cells through the type 3 secretion system. RipTPS is a conserved effector in the R. solanacearum species complex, and homologues were also detected in other bacterial plant pathogens. Functional analysis of RipTPS demonstrated that this type 3 effector synthesizes trehalose-6-phosphate and identified residues essential for this enzymatic activity. Although trehalose-6-phosphate is a key signal molecule in plants that regulates sugar status and carbon assimilation, the disruption of ripTPS did not alter the virulence of R. solanacearum on plants. However, heterologous expression assays showed that this effector specifically elicits a hypersensitive-like response on tobacco that is independent of its enzymatic activity and is triggered by the C-terminal half of the protein. Recognition of this effector by the plant immune system is suggestive of a role during the infectious process.Ralstonia solanacearum, the causal agent of bacterial wilt disease, infects more than two hundred plant species, including economically important crops. The type III secretion system plays a major role in the pathogenicity of this bacterium, and approximately 70 effector proteins have been shown to be translocated into host plant cells. This study provides the first description of a type III effector endowed with a trehalose-6-phosphate synthase enzymatic activity and illustrates a new mechanism by which the bacteria may manipulate the plant metabolism upon infection. In recent years, trehalose-6-phosphate has emerged as an essential signal molecule in plants, connecting plant metabolism and development. The finding that a bacterial pathogen could induce the production of trehalose-6-phosphate in plant cells further highlights the importance of this metabolite in multiple aspects of the molecular physiology of plants.

Dataset Information

The type III effector RipB from Ralstonia solanacearum RS1000 acts as a major avirulence factor in Nicotiana benthamiana and other Nicotiana species.

Publications

The type III effector RipB from Ralstonia solanacearum RS1000 acts as a major avirulence factor in Nicotiana benthamiana and other Nicotiana species.

Similar Datasets

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