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Cécile Segonzac,김완희,Hyelim Jeon,Kee Hoon Sohn 한국분자세포생물학회 2023 Molecules and cells Vol.46 No.11
The plant defense responses to microbial infection are tightly regulated and integrated with the developmental program for optimal resources allocation. Notably, the defense- associated hormone salicylic acid (SA) acts as a promoter of flowering while several plant pathogens actively target the flowering signaling pathway to promote their virulence or dissemination. Ralstonia pseudosolanacearum inject tens of effectors in the host cells that collectively promote bacterial proliferation in plant tissues. Here, we characterized the function of the broadly conserved R. pseudosolanacearum effector RipL, through heterologous expression in Arabidopsis thaliana . RipL-expressing transgenic lines presented a delayed flowering, which correlated with a low expression of flowering regulator genes. Delayed flowering was also observed in Nicotiana benthamiana plants transiently expressing RipL. In parallel, RipL promoted plant susceptibility to virulent strains of Pseudomonas syringae in the effector-expressing lines or when delivered by the type III secretion system. Unexpectedly, SA accumulation and SA-dependent immune signaling were not significantly affected by RipL expression. Rather, the RNA-seq analysis of infected RipL-expressing lines revealed that the overall amplitude of the transcriptional response was dampened, suggesting that RipL could promote plant susceptibility in an SA-independent manner. Further elucidation of the molecular mechanisms underpinning RipL effect on flowering and immunity may reveal novel effector functions in host cells.
Dhar, Souvik,Kim, Hyoujin,Segonzac, Cecile,Lee, Ji-Young Korean Society for Molecular and Cellular Biology 2021 Molecules and cells Vol.44 No.11
When perceiving microbe-associated molecular patterns (MAMPs) or plant-derived damage-associated molecular patterns (DAMPs), plants alter their root growth and development by displaying a reduction in the root length and the formation of root hairs and lateral roots. The exogenous application of a MAMP peptide, flg22, was shown to affect root growth by suppressing meristem activity. In addition to MAMPs, the DAMP peptide PEP1 suppresses root growth while also promoting root hair formation. However, the question of whether and how these elicitor peptides affect the development of the vascular system in the root has not been explored. The cellular receptors of PEP1, PEPR1 and PEPR2 are highly expressed in the root vascular system, while the receptors of flg22 (FLS2) and elf18 (EFR) are not. Consistent with the expression patterns of PEP1 receptors, we found that exogenously applied PEP1 has a strong impact on the division of stele cells, leading to a reduction of these cells. We also observed the alteration in the number and organization of cells that differentiate into xylem vessels. These PEP1-mediated developmental changes appear to be linked to the blockage of symplastic connections triggered by PEP1. PEP1 dramatically disrupts the symplastic movement of free green fluorescence protein (GFP) from phloem sieve elements to neighboring cells in the root meristem, leading to the deposition of a high level of callose between cells. Taken together, our first survey of PEP1-mediated vascular tissue development provides new insights into the PEP1 function as a regulator of cellular reprogramming in the Arabidopsis root vascular system.
Sohn, Kee Hoon,Segonzac, Cé,cile,Rallapalli, Ghanasyam,Sarris, Panagiotis F.,Woo, Joo Yong,Williams, Simon J.,Newman, Toby E.,Paek, Kyung Hee,Kobe, Bostjan,Jones, Jonathan D. G. Public Library of Science 2014 PLoS genetics Vol.10 No.10
<▼1><P>Plant nucleotide-binding leucine-rich repeat (NB-LRR) disease resistance (R) proteins recognize specific “avirulent” pathogen effectors and activate immune responses. NB-LRR proteins structurally and functionally resemble mammalian Nod-like receptors (NLRs). How NB-LRR and NLR proteins activate defense is poorly understood. The divergently transcribed Arabidopsis <I>R</I> genes, <I>RPS4</I> (resistance to <I>Pseudomonas syringae</I> 4) and <I>RRS1</I> (resistance to <I>Ralstonia solanacearum</I> 1), function together to confer recognition of <I>Pseudomonas</I> AvrRps4 and <I>Ralstonia</I> PopP2. <I>RRS1</I> is the only known recessive NB-LRR <I>R</I> gene and encodes a WRKY DNA binding domain, prompting suggestions that it acts downstream of RPS4 for transcriptional activation of defense genes. We define here the early RRS1-dependent transcriptional changes upon delivery of PopP2 <I>via Pseudomonas</I> type III secretion. The Arabidopsis <I>slh1</I> (<I>sensitive to low humidity 1</I>) mutant encodes an RRS1 allele (RRS1<SUP>SLH1</SUP>) with a single amino acid (leucine) insertion in the WRKY DNA-binding domain. Its poor growth due to constitutive defense activation is rescued at higher temperature. Transcription profiling data indicate that RRS1<SUP>SLH1</SUP>-mediated defense activation overlaps substantially with AvrRps4- and PopP2-regulated responses. To better understand the genetic basis of RPS4/RRS1-dependent immunity, we performed a genetic screen to identify <I><U>su</U>ppressor of</I><U>s</U>l<U>h</U>1 <I><U>i</U>mmunity</I> (<I>sushi</I>) mutants. We show that many <I>sushi</I> mutants carry mutations in <I>RPS4</I>, suggesting that RPS4 acts downstream or in a complex with RRS1. Interestingly, several mutations were identified in a domain C-terminal to the RPS4 LRR domain. Using an <I>Agrobacterium</I>-mediated transient assay system, we demonstrate that the P-loop motif of RPS4 but not of RRS1<SUP>SLH1</SUP> is required for RRS1<SUP>SLH1</SUP> function. We also recapitulate the dominant suppression of RRS1<SUP>SLH1</SUP> defense activation by wild type RRS1 and show this suppression requires an intact RRS1 P-loop. These analyses of RRS1<SUP>SLH1</SUP> shed new light on mechanisms by which NB-LRR protein pairs activate defense signaling, or are held inactive in the absence of a pathogen effector.</P></▼1><▼2><P><B>Author Summary</B></P><P>How plant NB-LRR resistance proteins and the related mammalian Nod-like receptors (NLRs) activate defense is poorly understood. Plant and animal immune receptors can function in pairs. Two Arabidopsis nuclear immune receptors, RPS4 and RRS1, confer recognition of the unrelated bacterial effectors, AvrRps4 and PopP2, and activate defense. Using delivery of PopP2 into Arabidopsis leaf cells <I>via Pseudomonas</I> type III secretion, we define early transcriptional changes upon RPS4/RRS1-dependent PopP2 recognition. We show an auto-active allele of RRS1, RRS1<SUP>SLH1</SUP>, triggers transcriptional reprogramming of defense genes that are also reprogrammed by AvrRps4 or PopP2 in an RPS4/RRS1-dependent manner. To discover genetic requirements for RRS1<SUP>SLH1</SUP> auto-activation, we conducted a suppressor screen. Many <I>suppressor of</I> slh1 <I>immunity</I> (<I>sushi</I>) mutants that are impaired in RRS1<SUP>SLH1</SUP>-mediated auto-activation carry loss-of-function mutations in RPS4. This suggests that RPS4 functions as a signaling component together with or downstream of RRS1-activated immunity, in contrast to earlier hypotheses, significantly advancing our understanding of how immune receptors activate defense in plants.</P></▼2>
Tackling multiple bacterial diseases of Solanaceae with a handful of immune receptors
Ho Bang Kim,최지현,Cécile Segonzac 한국원예학회 2022 Horticulture, Environment, and Biotechnology Vol.63 No.2
Every year, despite the use of chemicals, signifi cant crop loss is caused by pathogenic microbes. Plant innate resistance to pathogens depends on two sets of genetically encoded immune receptors that sense invaders and trigger signaling cascades leading to reinforcement of physical barriers and production of various antimicrobial compounds. In the past 30 years, the molecular cloning and characterization of plant immune receptors have deepened our understanding of the plant immune system and more importantly, have provided means to improve crop protection against devastating pathogens. Here, we review the molecular characterization of selected immune receptors that can detect multiple species of bacterial pathogens through an expanded recognition range, or through the detection of conserved pathogen activities or host targets. These recent structural and molecular insights about the activation of immune receptors provide the necessary framework to design their concomitant deployment in crops, in order to lower selective pressure on pathogen populations and prevent evasion from recognition. Hence, these few immune receptors emerge as high potential genetic resources to provide durable and environmentally safe protection against important bacterial diseases of solanaceous crops.
A Bacterial Tyrosine Phosphatase Inhibits Plant Pattern Recognition Receptor Activation
Macho, Alberto P.,Schwessinger, Benjamin,Ntoukakis, Vardis,Brutus, Alexandre,Segonzac, Cé,cile,Roy, Sonali,Kadota, Yasuhiro,Oh, Man-Ho,Sklenar, Jan,Derbyshire, Paul,Lozano-Durá,n, Rosa,Mal American Association for the Advancement of Scienc 2014 Science Vol.343 No.6178
<P><B>Move and Countermove</B></P><P>Receptors on plant cell surfaces are tuned to recognize molecular patterns associated with pathogenic bacteria. <B>Macho <I>et al.</I></B> (p. 1509; published online 13 March) found that activation of one of these receptors in <I>Arabidopsis</I> results in phosphorylation of a specific tyrosine residue, which in turn triggers the plant's immune response to the phytopathogen <I>Pseudomonas syringae. P. syringae</I> counters by secreting a specifically targeted phosphatase, thus stalling the plant's immune response.</P>
A Plant Immune Receptor Detects Pathogen Effectors that Target WRKY Transcription Factors
Sarris, Panagiotis F.,Duxbury, Z.,Huh, S.,Ma, Y.,Segonzac, C.,Sklenar, J.,Derbyshire, P.,Cevik, V.,Rallapalli, G.,Saucet, Simon B.,Wirthmueller, L.,Menke, Frank L.H.,Sohn, K.,Jones, Jonathan D.G. Cell Press ; MIT Press 2015 Cell Vol.161 No.5
Defense against pathogens in multicellular eukaryotes depends on intracellular immune receptors, yet surveillance by these receptors is poorly understood. Several plant nucleotide-binding, leucine-rich repeat (NB-LRR) immune receptors carry fusions with other protein domains. The Arabidopsis RRS1-R NB-LRR protein carries a C-terminal WRKY DNA binding domain and forms a receptor complex with RPS4, another NB-LRR protein. This complex detects the bacterial effectors AvrRps4 or PopP2 and then activates defense. Both bacterial proteins interact with the RRS1 WRKY domain, and PopP2 acetylates lysines to block DNA binding. PopP2 and AvrRps4 interact with other WRKY domain-containing proteins, suggesting these effectors interfere with WRKY transcription factor-dependent defense, and RPS4/RRS1 has integrated a ''decoy'' domain that enables detection of effectors that target WRKY proteins. We propose that NB-LRR receptor pairs, one member of which carries an additional protein domain, enable perception of pathogen effectors whose function is to target that domain.
Whole Genome Enabled Phylogenetic and Secretome Analyses of Two Venturia nashicola Isolates
Maxim Prokchorchik,Kyungho Won,Yoonyoung Lee,Cé,cile Segonzac,Kee Hoon Sohn 한국식물병리학회 2020 Plant Pathology Journal Vol.36 No.1
Venturia nashicola is a fungal pathogen causing scab disease in Asian pears. It is particularly important in the Northeast Asia region where Asian pears are intensively grown. Venturia nashicola causes disease in Asian pear but not in European pear. Due to the highly restricted host range of Venturia nashicola, it is hypothesized that the small secreted proteins deployed by the pathogen are responsible for the host determination. Here we report the whole genome based phylogenetic analysis and predicted secretomes for V. nashicola isolates. We believe that our data will provide a valuable information for further validation and functional characterization of host determinants in V. nashicola.