scholarly journals An oomycete RXLR effector triggers antagonistic plant hormone crosstalk to suppress host immunity

2019 ◽  
Author(s):  
Ryan Anderson ◽  
Devdutta Deb ◽  
John Withers ◽  
Sheng Yang He ◽  
John McDowell
Keyword(s):  
Plant Immunity ◽  
Effector Proteins ◽  
Type Iii Effectors ◽  
Hormone Crosstalk ◽  
Regulatory Cascade ◽  
Rxlr Effector ◽  
Plant Pathogen Interactions ◽  
Hyaloperonospora Arabidopsidis ◽  
Cell Networks ◽  
Bacterial Type

ABSTRACTUnderstanding the mechanisms through which pathogens alter plant cell networks is essential for understanding plant-pathogen interactions and will inform efforts to reduce crop diseases. Oomycetes secrete diverse effector proteins into plant cells. The mechanisms through which these effectors promote virulence are largely unknown. We show that the HaRxL10 effector protein from the Arabidopsis thaliana pathogen Hyaloperonospora arabidopsidis (Hpa) targets a transcriptional repressor (JAZ3) involved in jasmonic acid (JA) signalling. This manipulation activates a regulatory cascade that inhibits salicylic acid (SA) signalling, which normally restricts Hpa infection. This virulence mechanism is functionally equivalent to but mechanistically distinct from activation of the antagonistic JA-SA hormone crosstalk by the bacterial JA-mimicking toxin coronatine and by bacterial Type III effectors. These results reveal a key role for JAZ3 in plant immunity and emphasize that JA-SA crosstalk is an Achilles’ heel in the plant immune system, vulnerable to manipulation by diverse microbes.

scholarly journals Downy Mildew effector HaRxL21 interacts with the transcriptional repressor TOPLESS to promote pathogen susceptibility

2020 ◽  
Author(s):  
Sarah Harvey ◽  
Priyanka Kumari ◽  
Dmitry Lapin ◽  
Thomas Griebel ◽  
Richard Hickman ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Transcriptional Repression ◽  
Plant Immunity ◽  
Effector Proteins ◽  
Host Susceptibility ◽  
Close Relative ◽  
C Terminus ◽  
Rxlr Effector ◽  
Oomycete Pathogen ◽  
Hyaloperonospora Arabidopsidis

AbstractHyaloperonospora arabidopsidis (Hpa) is an oomycete pathogen causing Arabidopsis downy mildew. Effector proteins secreted from the pathogen into the plant play key roles in promoting infection by suppressing plant immunity and manipulating the host to the pathogen’s advantage. One class of oomycete effectors share a conserved ‘RxLR’ motif critical for their translocation into the host cell. Here we characterize the interaction between an RxLR effector, HaRxL21 (RxL21), and the Arabidopsis transcriptional co-repressor Topless (TPL). We establish that RxL21 and TPL interact via an EAR motif at the C-terminus of the effector, mimicking the host plant mechanism for recruiting TPL to sites of transcriptional repression. We show that this motif, and hence interaction with TPL, is necessary for the virulence function of the effector. Furthermore, we provide evidence that RxL21 uses the interaction with TPL, and its close relative TPL-related 1, to repress plant immunity and enhance host susceptibility to both biotrophic and necrotrophic pathogens.

scholarly journals The RXLR Effector PcAvh1 Is Required for Full Virulence of Phytophthora capsici

2019 ◽  
Vol 32 (8) ◽  
pp. 986-1000 ◽  
Author(s):  
Xiao-Ren Chen ◽  
Ye Zhang ◽  
Hai-Yang Li ◽  
Zi-Hui Zhang ◽  
Gui-Lin Sheng ◽  
...  
Keyword(s):  
Plant Pathogens ◽  
Plant Immunity ◽  
Phytophthora Capsici ◽  
Ectopic Expression ◽  
Plant Cells ◽  
Effector Proteins ◽  
Bell Pepper ◽  
Broad Host Range ◽  
Virus Induced Gene Silencing ◽  
Rxlr Effector

Plant pathogens employ diverse secreted effector proteins to manipulate host physiology and defense in order to foster diseases. The destructive Phytophthora pathogens encode hundreds of cytoplasmic effectors, which are believed to function inside the plant cells. Many of these cytoplasmic effectors contain the conserved N-terminal RXLR motif. Understanding the virulence function of RXLR effectors will provide important knowledge of Phytophthora pathogenesis. Here, we report the characterization of RXLR effector PcAvh1 from the broad–host range pathogen Phytophthora capsici. Only expressed during infection, PcAvh1 is quickly induced at the early infection stages. CRISPR/Cas9-knockout of PcAvh1 in P. capsici severely impairs virulence while overexpression enhances disease development in Nicotiana benthamiana and bell pepper, demonstrating that PcAvh1 is an essential virulence factor. Ectopic expression of PcAvh1 induces cell death in N. benthamiana, tomato, and bell pepper. Using yeast two-hybrid screening, we found that PcAvh1 interacts with the scaffolding subunit of the protein phosphatase 2A (PP2Aa) in plant cells. Virus-induced gene silencing of PP2Aa in N. benthamiana attenuates resistance to P. capsici and results in dwarfism, suggesting that PP2Aa regulates plant immunity and growth. Collectively, these results suggest that PcAvh1 contributes to P. capsici infection, probably through its interaction with host PP2Aa.

scholarly journals Intra-strain elicitation and suppression of plant immunity by Ralstonia solanacearum type-III effectors in Nicotiana benthamiana

2019 ◽  
Author(s):  
Yuying Sang ◽  
Wenjia Yu ◽  
Haiyan Zhuang ◽  
Yali Wei ◽  
Lida Derevnina ◽  
...  
Keyword(s):  
Immune System ◽  
Immune Responses ◽  
Ralstonia Solanacearum ◽  
Plant Immunity ◽  
Plant Cells ◽  
Effector Proteins ◽  
Type Iii Effectors ◽  
Plant Immune System ◽  
Successful Infection ◽  
Genes Encoding

AbstractEffector proteins delivered inside plant cells are powerful weapons for bacterial pathogens, but this exposes the pathogen to potential recognition by the plant immune system. Therefore, the effector repertoire of a given pathogen must be balanced for a successful infection. Ralstonia solanacearum is an aggressive pathogen with a large repertoire of secreted effectors. One of these effectors, RipE1, is conserved in most R. solanacearum strains sequenced to date. In this work, we found that RipE1 triggers immunity in N. benthamiana, which requires the immune regulator SGT1, but not EDS1 or NRCs. Interestingly, RipE1-triggered immunity induces the accumulation of salicylic acid (SA) and the overexpression of several genes encoding phenylalanine-ammonia lyases (PALs), suggesting that the unconventional PAL-mediated pathway is responsible for the observed SA biosynthesis. Surprisingly, RipE1 recognition also induces the expression of jasmonic acid (JA)-responsive genes and JA biosynthesis, suggesting that both SA and JA may act cooperatively in response to RipE1. Finally, we found that RipE1 expression leads to the accumulation of glutathione in plant cells, which precedes the activation of immune responses. R. solanacearum encodes another effector, RipAY, which is known to inhibit immune responses by degrading cellular glutathione. Accordingly, we show that RipAY inhibits RipE1-triggered immune responses. This work shows a strategy employed by R. solanacearum to counteract the perception of its effector proteins by the plant immune system.

scholarly journals A Phytophthora effector recruits a host cytoplasmic transacetylase into nuclear speckles to enhance plant susceptibility

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Haiyang Li ◽  
Haonan Wang ◽  
Maofeng Jing ◽  
Jinyi Zhu ◽  
Baodian Guo ◽  
...  
Keyword(s):  
Root Rot ◽  
Plant Immunity ◽  
Phytophthora Sojae ◽  
Host Immunity ◽  
Effector Proteins ◽  
Nuclear Speckles ◽  
Rxlr Effector ◽  
Plant Susceptibility

Oomycete pathogens secrete host cell-entering effector proteins to manipulate host immunity during infection. We previously showed that PsAvh52, an early-induced RxLR effector secreted from the soybean root rot pathogen, Phytophthora sojae, could suppress plant immunity. Here, we found that PsAvh52 is required for full virulence on soybean and binds to a novel soybean transacetylase, GmTAP1, in vivo and in vitro. PsAvh52 could cause GmTAP1 to relocate into the nucleus where GmTAP1 could acetylate histones H2A and H3 during early infection, thereby promoting susceptibility to P. sojae. In the absence of PsAvh52, GmTAP1 remained confined to the cytoplasm and did not modify plant susceptibility. These results demonstrate that GmTAP1 is a susceptibility factor that is hijacked by PsAvh52 in order to promote epigenetic modifications that enhance the susceptibility of soybean to P. sojae infection.

scholarly journals The Proteasome Acts as a Hub for Plant Immunity and Is Targeted by Pseudomonas Type III Effectors

2016 ◽  
Vol 172 (3) ◽  
pp. 1941-1958 ◽  
Author(s):  
Suayib Üstün ◽  
Arsheed Sheikh ◽  
Selena Gimenez-Ibanez ◽  
Alexandra Jones ◽  
Vardis Ntoukakis ◽  
...  
Keyword(s):  
Plant Immunity ◽  
Type Iii Effectors ◽  
Type Iii

scholarly journals Multiple Candidate Effectors from the Oomycete Pathogen Hyaloperonospora arabidopsidis Suppress Host Plant Immunity

2011 ◽  
Vol 7 (11) ◽  
pp. e1002348 ◽  
Author(s):  
Georgina Fabro ◽  
Jens Steinbrenner ◽  
Mary Coates ◽  
Naveed Ishaque ◽  
Laura Baxter ◽  
...  
Keyword(s):  
Host Plant ◽  
Plant Immunity ◽  
Oomycete Pathogen ◽  
Hyaloperonospora Arabidopsidis

scholarly journals Deciphering the mode of action and host recognition of bacterial type III effectors

2010 ◽  
Vol 37 (10) ◽  
pp. 926 ◽  
Author(s):  
Selena Gimenez-Ibanez ◽  
Dagmar R. Hann ◽  
John P. Rathjen
Keyword(s):  
Mode Of Action ◽  
Pathogenic Bacteria ◽  
Plant Immunity ◽  
Plant Defence ◽  
Host Recognition ◽  
Type Iii Effectors ◽  
Host Cytoplasm ◽  
Host Plasma Membrane ◽  
Defence Responses ◽  
Bacterial Effectors

Plant pathogenic bacteria adhere to cell walls and remain external to the cell throughout the pathogenic lifecycle, where they elicit host immunity through host plasma membrane localised receptors. To be successful pathogens, bacteria must suppress these defence responses, which they do by secreting a suite of virulence effector molecules into the host cytoplasm. However, effectors themselves can act as elicitors after perception by intracellular host immune receptors, thus, re-activating plant immunity. Bacterial effectors generally target host molecules through specific molecular activities to defeat plant defence responses. Although effectors can be used as tools to elucidate components of plant immunity, only a handful of these molecular targets are known and much remains to be learnt about effector strategies for bacterial pathogenicity. This review highlights recent advances in our understanding of the mode of action of bacterial effectors, which in the future will lead to improvements in agriculture.

scholarly journals Bridging the Gap: Type III Secretion Systems in Plant-Beneficial Bacteria

2022 ◽  
Vol 10 (1) ◽  
pp. 187
Author(s):  
Antoine Zboralski ◽  
Adrien Biessy ◽  
Martin Filion
Keyword(s):  
Type Iii Secretion ◽  
Plant Pathogens ◽  
Plant Immunity ◽  
Effector Proteins ◽  
Secretion Systems ◽  
Beneficial Bacteria ◽  
Living Plant ◽  
Pseudomonas Spp ◽  
Type Iii ◽  
Type Iii Secretion Systems

Type III secretion systems (T3SSs) are bacterial membrane-embedded nanomachines translocating effector proteins into the cytoplasm of eukaryotic cells. They have been intensively studied for their important roles in animal and plant bacterial diseases. Over the past two decades, genome sequencing has unveiled their ubiquitous distribution in many taxa of Gram-negative bacteria, including plant-beneficial ones. Here, we discuss the distribution and functions of the T3SS in two agronomically important bacterial groups: the symbiotic nodule-forming nitrogen-fixing rhizobia and the free-living plant-beneficial Pseudomonas spp. In legume-rhizobia symbiosis, T3SSs and their cognate effectors play important roles, including the modulation of the plant immune response and the initiation of the nodulation process in some cases. In plant-beneficial Pseudomonas spp., the roles of T3SSs are not fully understood, but pertain to plant immunity suppression, biocontrol against eukaryotic plant pathogens, mycorrhization facilitation, and possibly resistance against protist predation. The diversity of T3SSs in plant-beneficial bacteria points to their important roles in multifarious interkingdom interactions in the rhizosphere. We argue that the gap in research on T3SSs in plant-beneficial bacteria must be bridged to better understand bacteria/eukaryotes rhizosphere interactions and to support the development of efficient plant-growth promoting microbial inoculants.

scholarly journals Genome context influences evolutionary flexibility of nearly identical type III effectors in two phytopathogenic Pseudomonads

2021 ◽  
Author(s):  
David A Baltrus ◽  
Qian Feng ◽  
Brian H Kvitko
Keyword(s):  
Pseudomonas Syringae ◽  
Evolutionary Dynamics ◽  
Effector Proteins ◽  
In Planta ◽  
Genomic Context ◽  
Type Iii Effectors ◽  
Type Iii ◽  
Genome Context ◽  
The Impact ◽  
Multiple Type

Integrative Conjugative Elements (ICEs) are replicons that can insert and excise from chromosomal locations in a site specific manner, can conjugate across strains, and which often carry a variety of genes useful for bacterial growth and survival under specific conditions. Although ICEs have been identified and vetted within certain clades of the agricultural pathogen Pseudomonas syringae, the impact of ICE carriage and transfer across the entire P. syringae species complex remains underexplored. Here we identify and vet an ICE (PmaICE-DQ) from P. syringae pv. maculicola ES4326, a strain commonly used for laboratory virulence experiments, demonstrate that this element can excise and conjugate across strains, and contains loci encoding multiple type III effector proteins. Moreover, genome context suggests that another ICE (PmaICE-AOAB) is highly similar in comparison with and found immediately adjacent to PmaICE-DQ within the chromosome of strain ES4326, and also contains multiple type III effectors. Lastly, we present passage data from in planta experiments that suggests that genomic plasticity associated with ICEs may enable strains to more rapidly lose type III effectors that trigger R-gene mediated resistance in comparison to strains where nearly isogenic effectors are not present in ICEs. Taken together, our study sheds light on a set of ICE elements from P. syringae pv. maculicola ES4326 and highlights how genomic context may lead to different evolutionary dynamics for shared virulence genes between strains.

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