A conserved type III effector RipB is recognized in tobacco and contributes to Ralstonia solanacearum virulence in susceptible host plants

Cao, Peng; Chen, Jialan; Wang, Rongbo; Zhao, Ming; Zhang, Shuangxi; An, Yuyan; Liu, Peiqing; ZHANG, Mei-xiang

doi:10.1016/j.bbrc.2022.09.062

Cited by 7 publications

(6 citation statements)

References 32 publications

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“…Based on these data, we can speculate that in non-stressed pepper plants, due to the silencing of Ca16R, no immunity is activated; however, when the plants are challenged by RSI, the upregulated Ca16R activates SA immunity. These results are consistent with those of a previous study which found that 14-3-3s including SlTFT4 and SlTFT7 in tomato are targeted by effectors from R. solanacearum [20], indicating that multiple 14-3-3s might be involved in plant immunity against R. solanacearum. The immune response of plants is produced by a large amount of transcription reprogramming [37].…”

Section: Ca16r Acts Positively In Pepper Immunity Against Rsisupporting

confidence: 93%

“…14-3-3 proteins have been found to be involved in the regulation of plant immunity [9][10][11][12][13][14] by targeting NLRs [15], MAPKKKs [9,14,15], substrates of CDPKs [16], RIN4 and GCN4 [17], and transcription factors such as GRAS proteins (by regulating its stability) [18]. Their roles as crucial regulators in plant immunity is reflected in their frequent attack or hijacking by pathogen effectors to weaken plant immune responses or increase pathogen virulence [10,[19][20][21][22][23][24]. However, the roles of 14-3-3 proteins in plant immunity and the underlying mechanisms are not fully understood.…”

Section: Introductionmentioning

confidence: 99%

“…Both CaWRKY40 and CabZIP63 are modulated by other regulatory proteins post-translationally, for example, to activate pepper immunity, CaWRKY40 is regulated by CaWRKY28 [28] and CabZIP63 is modulated by CaASR1, an abscisic acid-, stress-, and ripening-inducible protein [33]. In addition, it has recently been found that the 14-3-3 proteins SlTFT4 and SlTFT7 have been targeted by R. solanacearum type III effectors to suppress host immunity [19,20], implying that 14-3-3 proteins might be involved in pepper immunity against R. solanacearum. However, no 14-3-3 protein has been found to play a role in pepper immunity against R. solanacearum.…”

Section: Introductionmentioning

confidence: 99%

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A 14-3-3 Protein Ca16R Acts Positively in Pepper Immunity against Ralstonia solanacearum by Interacting with CaASR1

Yang,

Wan,

Cheng

et al. 2024

Plants

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Although 14-3-3 proteins have been implicated in plant growth, development, and stress response, their roles in pepper immunity against R. solanacearum remain poorly understood. In this study, a 14-3-3-encoding gene in pepper, Ca16R, was found to be upregulated by R. solanacearum inoculation (RSI), its silencing significantly reduced the resistance of pepper plants to RSI, and its overexpression significantly enhanced the resistance of Nicotiana benthamiana to RSI. Consistently, its transient overexpression in pepper leaves triggered HR cell death, indicating that it acts positively in pepper immunity against RSI, and it was further found to act positively in pepper immunity against RSI by promoting SA but repressing JA signaling. Ca16R was also found to interact with CaASR1, originally using pull-down combined with a spectrum assay, and then confirmed using bimolecular fluorescence complementation (BiFC) and a pull-down assay. Furthermore, we found that CaASR1 transient overexpression induced HR cell death and SA-dependent immunity while repressing JA signaling, although this induction and repression was blocked by Ca16R silencing. All these data indicate that Ca16R acts positively in pepper immunity against RSI by interacting with CaASR1, thereby promoting SA-mediated immunity while repressing JA signaling. These results provide new insight into mechanisms underlying pepper immunity against RSI.

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Section: Ca16r Acts Positively In Pepper Immunity Against Rsisupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A 14-3-3 Protein Ca16R Acts Positively in Pepper Immunity against Ralstonia solanacearum by Interacting with CaASR1

Yang,

Wan,

Cheng

et al. 2024

Plants

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“…An effector typically promotes infection in susceptible hosts but triggers defense when recognized in certain hosts harboring the corresponding resistance genes. RipB from R. solanacearum serves as an avirulence determinant in N. benthamiana and is recognized by the resistance protein Roq1 (Cao et al., 2022; Nakano & Mukaihara, 2019b; Thomas et al., 2020). To access the suitability of the TMV‐GFP system for identifying avirulence effectors, we re‐evaluated RipB using this system.…”

Section: Resultsmentioning

confidence: 99%

A robust high‐throughput functional screening assay for plant pathogen effectors using the TMV‐GFP vector

Cao,

Shi,

Zhang

et al. 2024

The Plant Journal

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SUMMARYUncovering the function of phytopathogen effectors is crucial for understanding mechanisms of pathogen pathogenicity and for improving our ability to protect plants from diseases. An increasing number of effectors have been predicted in various plant pathogens. Functional characterization of these effectors has become a major focus in the study of plant–pathogen interactions. In this study, we designed a novel screening system that combines the TMV (tobacco mosaic virus)‐GFP vector and Agrobacterium‐mediated transient expression in the model plant Nicotiana benthamiana. This system enables the rapid identification of effectors that interfere with plant immunity. The biological function of these effectors can be easily evaluated by observing the GFP fluorescence signal using a UV lamp within just a few days. To evaluate the TMV‐GFP system, we initially tested it with well‐described virulence and avirulence type III effectors from the bacterial pathogen Ralstonia solanacearum. After proving the accuracy and efficiency of the TMV‐GFP system, we successfully screened a novel virulence effector, RipS1, using this approach. Furthermore, using the TMV‐GFP system, we reproduced consistent results with previously known cytoplasmic effectors from a diverse array of pathogens. Additionally, we demonstrated the effectiveness of the TMV‐GFP system in identifying apoplastic effectors. The easy operation, time‐saving nature, broad effectiveness, and low technical requirements of the TMV‐GFP system make it a promising approach for high‐throughput screening of effectors with immune interference activity from various pathogens.

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“…Recently, Yu et al (2022) found that RipAC inhibits pattern-triggered immunity by targeting E3 ubiquitin ligase plant U-box 4 (PUB4). Furthermore, core effector RipB acts as a major avirulence factor in Nicotiana species and suppresses the basal defense in susceptible hosts to promote pathogen infection ( Nakano and Mukaihara, 2019 ; Cao et al, 2022 ). In addition, the nuclear-localized effectors RipAB and RipX are involved in plant immune response ( Zheng et al, 2019 ; Sun et al, 2020 ).…”

Section: Resultsmentioning

confidence: 99%

Proposal to classify Ralstonia solanacearum phylotype I strains as Ralstonia nicotianae sp. nov., and a genomic comparison between members of the genus Ralstonia

Liu

Zhang

et al. 2023

Front. Microbiol.

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A Gram-negative, aerobic, rod-shaped, motile bacterium with multi-flagella, strain RST, was isolated from bacterial wilt of tobacco in Yuxi city of Yunnan province, China. The strain contains the major fatty acids of C16:0, summed feature 3 (C16:1ω7c and/or C16:1ω6c), and summed feature 8 (C18:1ω7c and/or C18:1ω6c). The polar lipid profile of strain RST consists of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and unidentified aminophospholipid. Strain RST contains ubiquinones Q-7 and Q-8. 16S rRNA gene sequence (1,407 bp) analysis showed that strain RST is closely related to members of the genus Ralstonia and shares the highest sequence identities with R. pseudosolanacearum LMG 9673T (99.50%), R. syzygii subsp. indonesiensis LMG 27703T (99.50%), R. solanacearum LMG 2299T (99.28%), and R. syzygii subsp. celebesensis LMG 27706T (99.21%). The 16S rRNA gene sequence identities between strain RST and other members of the genus Ralstonia were below 98.00%. Genome sequencing yielded a genome size of 5.61 Mbp and a G + C content of 67.1 mol%. The genomic comparison showed average nucleotide identity (ANIb) values between strain RST and R. pseudosolanacearum LMG 9673T, R. solanacearum LMG 2299T, and R. syzygii subsp. indonesiensis UQRS 627T of 95.23, 89.43, and 91.41%, respectively, and the corresponding digital DNA–DNA hybridization (dDDH) values (yielded by formula 2) were 66.20, 44.80, and 47.50%, respectively. In addition, strains belonging to R. solanacearum phylotype I shared both ANIb and dDDH with strain RST above the species cut-off values of 96 and 70%, respectively. The ANIb and dDDH values between the genome sequences from 12 strains of R. solanacearum phylotype III (Current R. pseudosolanacearum) and those of strain RST were below the species cut-off values. Based on these data, we concluded that strains of phylotype I, including RST, represent a novel species of the genus Ralstonia, for which the name Ralstonia nicotianae sp. nov. is proposed. The type strain of Ralstonia nicotianae sp. nov. is RST (=GDMCC 1.3533T = JCM 35814T).

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A conserved type III effector RipB is recognized in tobacco and contributes to Ralstonia solanacearum virulence in susceptible host plants

Cited by 7 publications

References 32 publications

A 14-3-3 Protein Ca16R Acts Positively in Pepper Immunity against Ralstonia solanacearum by Interacting with CaASR1

A 14-3-3 Protein Ca16R Acts Positively in Pepper Immunity against Ralstonia solanacearum by Interacting with CaASR1

A robust high‐throughput functional screening assay for plant pathogen effectors using the TMV‐GFP vector

Proposal to classify Ralstonia solanacearum phylotype I strains as Ralstonia nicotianae sp. nov., and a genomic comparison between members of the genus Ralstonia

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