====== XopX ====== Author: [[https://www.researchgate.net/profile/Lucas_Moriniere|Lucas Morinière]] & [[https://www.researchgate.net/profile/Sohini_Deb|Sohini Deb]]\\ Internal reviewer: Coline Sciallano\\ Expert reviewer: Ramesh V. Sonti Class: XopX\\ Family: XopX\\ Prototype: XopX (//Xanthomonas euvesicatoria// pv. //euvesicatoria//, ex //Xanthomonas campestris// pv. //vesicatoria//; strain 85-10)\\ RefSeq ID: [[https://www.ncbi.nlm.nih.gov/protein/WP_011346212.1|WP_011346212.1]] (699 aa)\\ 3D structure: Unknown ===== Biological function ===== === How discovered? === XopX was discovered through the screening of a genomic cosmid library of //X. euvesicatoria// strain GM98-38 conjugated in //X. campestris// pv. //campestris// that allowed //Xcc// to elicit an //Xcv // cell death-like response when inoculated on //N. benthamiana// (Metz // et al//., 2005). === (Experimental) evidence for being a T3E === Translational fusions of XopX with the calmodulin-dependent adenylate cyclase domain of //Bordetella pertussis// (Cya) were exchanged by simple homologous recombination into the genomic copy of //xopX// of //X. euvesicatoria// strains 85* (constitutive //hrp// expression mutant), 85* Δ//hrcV// (T3SS-defective mutant) and wild-type GM98-38. All Cya fusion strains except 85* Δ//hrcV// still induced cell death response activity in //N. benthamiana//. Moreover, leaf extracts of //N. benthamiana// inoculated with these fusion strains were assayed for cAMP, and only strains with a functional T3SS showed an increase in cAMP levels due to translocation of the Cya reporter protein into the plant (Metz //et al//., 2005). === Regulation === qRT-PCR revealed that transcript levels of 15 out of 18 tested non-TAL effector genes (as well as the regulatory genes //hrpG// and //hrpX//), including //xopX//, were significantly reduced in the //Xanthomonas oryzae// pv. //oryzae// Δ//xrvC// mutant compared with those in the wild-type strain PXO99^A (Liu //et al.//, 2016). === Phenotypes === * XopX was demonstrated to be cytotoxic when expressed in yeast, suggesting it may target a conserved eukaryotic cell process required for cell viability (Salomon //et al//., 2011). * During infection of rice (//Oryza sativa//) with //Xanthomonas oryzae// pv. //oryzae//, XopX was shown to be an inhibitor of rice innate immune response, as it suppresses LipA-induced callose deposition (Sinha //et al//., 2013). * XopX is required for the development of //X. euvesicatoria//- induced symptoms in the bacterial spot disease of tomato (//Solanum lycopersicum//) and pepper (//Capsicum annuum//). Indeed, it promotes ethylene production, and therefore chlorosis and plant cell death during infection by //X. euvesicatoria// of susceptible tomato and in transient expression assays in tobacco. Interestingly, it also suppresses flagellin-induced production of reactive oxygen species (ROS) while promoting the accumulation of pattern-triggered immunity (PTI) gene transcripts (Stork //et al//., 2015). Eventually, the complex behavior of XopX //in planta//, which combines activation and suppression of immunity-related plant responses at the same time, allows to classify this effector with the T3Es that activates the plant ‘default to death and defense’ response (Lindeberg //et al//., 2012; Stork //et al//., 2015). * XopX is required for full virulence in //Xanthomonas ////axonopodis// //pv. manihotis//CIO151 strain//. A Xam// strain deleted for //xopX// showed decreased ability to produce symptoms in leaves of cassava. Also, the// xopX //KO reached more than one log unit lower populations than those observed for the wild‐type strain. This underlies the importance of this effector for disease developement (Medina //et al., //2018). * When expressed in //Pseudomonas fluorescens //55 (//Pf //55), a non‐pathogenic bacterium capable of eliciting PTI (callose deposit) in //Arabidopsis //Col‐0 plants, XopX is not able to reduce callose deposit, suggesting in these conditions, the effector is not able to suppress PTI. Using the same heterologuous system, XopX is not able to suppress the HR triggered by Pf 55 HopA1 on tobacco, suggesting that is these conditions, XopX do not act as an ETI suppressor. (Medina //et al//., 2018). * When transiently expressed in //N. benthamiana by Agrobacterium tumefaciens//–mediated expression system, XopX from //X. oryzae //pv. //oryzicola// cause the nonhost HR at approximately 2 days (Li// et al., //2015). * //A ∆xopX// mutant strain of //Xanthomonas phaseoli //pv. //manihotis// (aka //Xanthomonas axonopodis //pv. //manihotis//) showed reduced growth //in planta// and delayed spread through the vasculature system of cassava (Mutka et al.//, 2016). // * //Agrobacterium//- mediated transient expression of both //Xanthomonasoryzae //pv.//oryzae//XopQ and XopX in rice cells resulted in induction of rice immune responses. These immune responses were not observed when either protein was individually expressed in rice cells. XopQ-XopX induced rice immune responses were not observed with a XopX mutant that is defective in 14-3-3 binding (Deb //et al.//, 2020). * A screen for //Xanthomonas oryzae//pv.// oryzae// effectors which can suppress XopQ-XopX induced rice immune responses, led to the identification of five effectors, namely XopU, XopV, XopP, XopG and AvrBs2, that could individually suppress these immune responses. These results suggest a complex interplay of //Xanthomonas //T3SS effectors in suppression of both pathogen-triggered immunity and effector-triggered immunity to promote virulence on rice (Deb //et al.//, 2020). * XopX(ACD57163) is one among the five classes of virulence genes found to be upregulated in the//Xanthomonas oryzae//pv.//oryzae//MAI1 strain during infection.//xopX//was up-regulated at both 3 and 6 dai(Soto-Suárez //et al.//, 2010). * The //xopX// gene contributes to the virulence of //Xanthomonas campestris// pv. //vesicatoria //on hosts pepper and tomato. XopX targets the innate immune response, resulting in enhanced plant disease susceptibility (Metz //et al////.//, 2005). * A //Xanthomonas campestris //pv.//vesicatoria////xopX //mutant strain could not induce cell death response in//N. benthamiana//, and could be complemented back to cell death response on//N. benthamiana//in trans with plasmid subclones of//xopX//(Metz// et al//.//, //2005). === Localization === //Xanthomonas oryzae //pv. //oryzae //XopX wild-type protein localizes mostly to the nucleus, but is also present to a lesser extent in the peripheral cytoplasm. However, the XopX S193A and XopX S477A mutants of XopX, that are defective in binding to the rice 14-3-3 proteins GF14d and GF14e, were found to be unable to localize to the nucleus, and were mostly observed in the cytoplasm (Deb //et al.//, 2020). === Enzymatic function === Unknown. === Interaction partners === * It has been suggested that XopX-triggering of plant cell death response was dependent on another cofactor delivered by the T3SS, yet still unknown (Metz //et al.//, 2005). * The //Xanthomonas oryzae //pv. //oryzae //XopX interacts with two of the eight rice 14-3-3 proteins, GF14d and GF14e. Mutants of XopX that are defective in 14-3-3 binding are also defective in suppression of immune responses, suggesting that interaction with 14-3-3 proteins is required for suppression of host innate immunity (Deb //et al.//, 2020). * Yeast two-hybrid, bimolecular fluorescence complementation (BiFC) and co-IP assays indicate that the //Xanthomonas oryzae //pv.// oryzae// XopX interacts with the type III effector XopQ (Deb//et al.//, 2020). === Conservation === **In xanthomonads** Yes, xopX homologs can be found in almost every sequenced //Xanthomonas// spp. strain, except //X. albilineans// and //X. sacchari//, making it an ancient //Xanthomonas// core T3E (Stork //et al.//, 2015). **In other plant pathogens/symbionts ** Related proteins (query cover > 80% and percent identity > 50 %) can be detected in several unclassified Burkholderiales (//Xylophilus ampelinus, Rivibacter// sp., //Rhizobacter //sp., //Mitsuaria //sp.) and in the Comamonadaceae (//Hydrogenophaga taeniospiralis//). === References === Deb S, Ghosh P, Patel HK, Sonti RV (2020). Interaction of the Xanthomonas effectors XopQ and XopX results in induction of rice immune responses. Plant J. 104: 332-350. DOI: [[https://doi.org/10.1111/tpj.14924|10.1111/tpj.14924]] Li S, Wang Y, Wang S, Fang A, Wang J, Liu L, Zhang K, Mao Y, Sun W (2015). The type III effector AvrBs2 in //Xanthomonas oryzae //pv. //oryzicola //suppresses rice immunity and promotes disease development. Mol. Plant Microbe Interact. 28: 869-880. DOI: [[https://doi.org/10.1094/MPMI-10-14-0314-R|10.1094/MPMI-10-14-0314-R]] Lindeberg M, Cunnac S, Collmer A (2012). Pseudomonassyringae type III effector repertoires: last words in endless arguments. Trends Microbiol. 20: 199-208. DOI: [[https://doi.org/10.1016/j.tim.2012.01.003|10.1016/j.tim.2012.01.003]] Liu Y, Long J, Shen D, Song C (2016). //Xanthomonas oryzae //pv. //oryzae //requires H-NS-family protein XrvC to regulate virulence during rice infection. FEMS Microbiol. Lett. 363: fnw067. DOI: [[https://doi.org/10.1093/femsle/fnw067|10.1093/femsle/fnw067]] Medina CA, Reyes PA, Trujillo CA, Gonzalez JL, Bejarano DA, Montenegro NA, Jacobs JM, Joe A, Restrepo S, Alfano JR, Bernal A (2018). The role of type III effectors from //Xanthomonas axonopodis //pv. //manihotis// in virulence and suppression of plant immunity. Mol. Plant Pathol. 19: 593-606. DOI: [[https://doi.org/10.1111/mpp.12545|10.1111/mpp.12545]] Metz M, Dahlbeck D, Morales CQ, Sady BA, Clark ET, Staskawicz BJ (2005). The conserved// Xanthomonas campestris// pv. //vesicatoria //effector protein XopX is a virulence factor and suppresses host defense in //Nicotiana benthamiana//. Plant J. 41: 801-814. DOI: [[https://doi.org/10.1111/j.1365-313X.2005.02338.x|10.1111/j.1365-313X.2005.02338.x]] Mutka AM, Fentress SJ, Sher JW, Berry JC, Pretz C, Nusinow DA, Bart R (2016). Quantitative, image-based phenotyping methods provide insight into spatial and temporal dimensions of plant disease. Plant Physiol. 172: 650-660. DOI: [[https://doi.org/10.1104/pp.16.00984|10.1104/pp.16.00984]] Salomon D, Dar D, Sreeramulu S, Sessa G (2011). Expression of //Xanthomonas campestris// pv. //vesicatoria// type III effectors in yeast affects cell growth and viability. Mol. Plant. Microbe Interact. 24: 305-314. DOI: [[https://doi.org/10.1094/MPMI-09-10-0196|10.1094/MPMI-09-10-0196]] Sinha D, Gupta MK, Patel HK, Ranjan A, Sonti RV (2013). Cell wall degrading enzyme induced rice innate immune responses are suppressed by the type 3 secretion system effectors XopN, XopQ, XopX and XopZ of //Xanthomonas oryzae //pv. //oryzae//. PLoS One 8: e75867. DOI: [[https://doi.org/10.1371/journal.pone.0075867|10.1371/journal.pone.0075867]] Soto-Suárez M, Bernal D, González C, Szurek B, Guyot R, Tohme J, Verdier V. In planta gene expression analysis of //Xanthomonas oryzae //pathovar //oryzae//, African strain MAI1. BMC Microbiol. 2010 Jun 11;10:170. DOI: 10.1186/1471-2180-10-170. Stork W, Kim JG, Mudgett MB (2015). Functional analysis of plant defense suppression and activation by the Xanthomonas core type III effector XopX. Mol. Plant. Microbe Interact. 28: 180-194. DOI: [[https://doi.org/10.1094/MPMI-09-14-0263-R|10.1094/MPMI-09-14-0263-R]]