====== The Type III Effector XopE2 from //Xanthomonas// ======

Author: [[https://www.researchgate.net/profile/Jaime_Cubero|Jaime Cubero]]\\
Internal reviewer: [[https://www.researchgate.net/profile/Eran_Bosis|Eran Bosis]]\\
Expert reviewer: [[https://www.researchgate.net/profile/Ralf_Koebnik|Ralf Koebnik]]

Class: XopE\\
Family: XopE2\\
Prototype: XCV2280 (//Xanthomonas euvesicatoria// pv. //euvesicatoria//, ex //Xanthomonas campestris// pv. //vesicatoria//; strain 85-10)\\
GenBank ID: [[https://www.ncbi.nlm.nih.gov/protein/CAJ23957.1|CAJ23957.1]] (358 aa)\\
RefSeq ID: [[https://www.ncbi.nlm.nih.gov/protein/WP_011347479.1|WP_011347479.1]] (358 aa)\\
Synonym: AvrXacE3 (//Xanthomonas citri// pv. //citri//); AvrXccE1 (//Xanthomonas campestris// pv. //campestris//)\\
3D structure: Myristoylation motif at the extreme N terminus (Thieme //et al.//, 2007).

===== Biological function =====

=== How discovered? ===

XopE2 was first identified by sequence homology searches (da Silva //et al//., 2002 (XACb0011); Thieme //et al//. 2005; Thieme //et al//., 2007).
=== (Experimental) evidence for being a T3E ===

XopE2 fused to the AvrBs3 reporter was shown to translocate into plant cells in an //hrpF//-dependent manner (Thieme //et al//., 2007).
=== Regulation ===

XopE2 from //X. euvesicatoria// was found to be regulated by HrpG and HrpX, its promoter contains a PIP BOX and it is coregulated with the T3 secretion machinery (Thieme //et al//., 2007).
=== Phenotypes ===

  * XopE2 shows an avirulence activity in //Solanum pseudocapsicum//  (Thieme //et al.//, 2007).
  * //Agrobacterium//  mediated transient expression of XopE2 shows avirulence activity in the ornamental plant //S. pseudocapsicum//  (Lin //et al//., 2011).
  * XopE2 proteins were shown to be capable of suppressing the hypersensitive response (HR) of //Nicotiana//  spp. induced by HopPsyA of //P. syringae //pv. //syringae//  61 and the reaction occurs within the plant cells after their delivery by TTSS (Lin //et al//., 2011).
  * XopE2 inhibits growth of yeast cells in the presence of sodium chloride and caffeine (Salomon //et al//., 2011).
  * Expression of XopE2 in yeast affects the yeast cell wall and the endoplasmic reticulum stress response (Bosis //et al//., 2011).
  * XopE2 appears to promote wall-bound invertase activity in pepper leaves (Sonnewald //et al.//, 2011).
  * XopE2 mutants grow to equivalent titers as wild type //X. euvesicatoria//  in tomato leaves indicating that is not required for bacterial multiplication in planta. XopE2 together with XopE1 and XopO may function redundantly to inhibit //X//. //euvesicatoria//  induced chlorosis in tomato leaves (Dubrow //et al//., 2018).
  * XopE2 inhibits the activation of a PTI-inducible promoter by the bacterial peptide elf18 in //Arabidopsis //protoplasts and by flg22 in tomato protoplasts. This effector inhibits flg22-induced callose deposition //in planta //and enhanced disease symptoms caused by attenuated //Pseudomonas syringae//  bacteria (Popov //et al//., 2016).
  * XopE2//<sub>Xcc</sub> //  was found to trigger immune responses in //Arabidopsis//  via an unidentified activator of the salicylic acid signaling pathway (Huang //et al.//, 2024).
  * Proper subcellular localization of XopE2//<sub>Xcc</sub> //  to the plant plasma membrane via its N-myristoylation motif is required to induce expression of defense response-associated genes in //Arabidopsis//  (Huang //et al.//, 2024)

=== Localization ===

XopE2 fused to GFP in a binary vector under control of the Cauliflower mosaic virus 35S promoter expressed in //Nicotiana benthamiana//  leaves, using //Agrobacterium//-mediated gene transfer, allowed to localize XopE2::GFP confined to the periphery of the cells and not detectable in the nucleus or in the cytoplasm. Localization of the XopE2::GFP to the plasma membrane of //N. benthamiana //mesophyll cells could be confirmed by immunocytochemistry (Thieme //et al//., 2007). The N-myristoylation motif is essential for the subcellular localization to the plant plasma membrane of XopE2//<sub>Xcc</sub> //  (Huang //et al.//, 2024).

=== Enzymatic function ===

XopE2 belongs to the HopX effector family, which are part of the transglutaminase superfamily (Nimchuk //et al//., 2007).

=== Interaction partners ===

XopE2 was found to physically interact with tomato 14-3-3 (TFT) proteins. XopE2 is phosphorylated at multiple residues //in planta //for maximal binding to TFT10 (Dubrow //et al//., 2018).

===== Conservation =====

**In xanthomonads**

Yes (//e.g.//, //X. citri, X. campestris, X. phaseoli, X. alfalfa, X. euvesicatoria//).

=== In other plant pathogens/symbionts ===

Yes (//Pseudomonas//, //Ralstonia//).

===== References =====

Assis RAB, Polloni LC, Patané JSL, Thakur S, Felestrino ÉB, Diaz-Caballero J, Digiampietri LA, Goulart LR, Almeida NF, Nascimento R, Dandekar AM, Zaini PA, Setubal JC, Guttman DS, Moreira LM (2017). Identification and analysis of seven effector protein families with different adaptive and evolutionary histories in plant-associated members of the //Xanthomonadaceae//. Sci. Rep. 7: 16133. DOI: [[https://doi.org/10.1038/s41598-017-16325-1|10.1038/s41598-017-16325-1]]

Bosis E, Salomon D, Sessa G (2011). A simple yeast-based strategy to identify host cellular processes targeted by bacterial effector proteins. PLoS One 6: e27698. DOI: [[https://dx.doi.org/10.1371/journal.pone.0027698|10.1371/journal.pone.0027698]]

da Silva AC, Ferro JA, Reinach FC, Farah CS, Furlan LR, Quaggio RB, Monteiro-Vitorello CB, Van Sluys MA, Almeida NF, Alves LM, do Amaral AM, Bertolini MC, Camargo LE, Camarotte G, Cannavan F, Cardozo J, Chambergo F, Ciapina LP, Cicarelli RM, Coutinho LL, Cursino-Santos JR, El Dorry H, Faria JB, Ferreira AJ, Ferreira RC, Ferro MI, Formighieri EF, Franco MC, Greggio CC, Gruber A, Katsuyama AM, Kishi LT, Leite RP, Lemos EG, Lemos MV, Locali EC, Machado MA, Madeira AM, Martinez-Rossi NM, Martins EC, Meidanis J, Menck CF, Miyaki CY, Moon DH, Moreira LM, Novo MT, Okura VK, Oliveira, MC, Oliveira VR, Pereira HA, Rossi A, Sena JA, Silva C, de Souza RF, Spinola LA,Takita MA, Tamura RE, Teixeira EC, Tezza RI, Trindade dos SM, Truffi D, Tsai, SM, White FF, Setubal JC, Kitajima JP (2002). Comparison of the genomes of two //Xanthomonas// pathogens with differing host specificities. Nature 417: 459-463. DOI: [[https://doi.org/10.1038/417459a|10.1038/417459a]]

Dubrow Z, Sunitha S, Kim JG, Aakre CD, Girija AM, Sobol G, Teper D, Chen YC, Ozbaki-Yagan N, Vance H, Sessa G, Mudgett MB (2018). Tomato 14-3-3 proteins are required for //Xv3// disease resistance and interact with a subset of //Xanthomonas euvesicatoria// effectors. Mol. Plant Microbe Interact. 31: 1301-1311. DOI: [[https://doi.org/10.1094/MPMI-02-18-0048-R|10.1094/MPMI-02-18-0048-R]]

Huang J, Zhou H, Zhou M, Li N, Jiang B, He Y (2024). Functional analysis of type III effectors in //Xanthomonas campestris// pv. //campestris// reveals distinct roles in modulating //Arabidopsis// innate immunity. Pathogens 13: 448. DOI: [[https://doi.org/10.3390/pathogens13060448|10.3390/pathogens13060448]]

Lin RH, Peng CW, Lin YC, Peng HL, Huang HC (2011). The XopE2 effector protein of //Xanthomonas campestris// pv. vesicatoria is involved in virulence and in the suppression of the hypersensitive response. Bot. Stud. 52: 55-72. [[https://www.researchgate.net/publication/286363598_The_XopE2_effector_protein_of_Xanthomonas_campestris_pv_vesicatoria_is_involved_in_virulence_and_in_the_suppression_of_the_hypersensitive_response|Link]]

Nimchuk ZL, Fisher EJ, Desvaux D, Chang JH, Dangl JL (2007). The HopX (AvrPphE) family of //Pseudomonas syringae// type III effectors require a catalytic triad and a novel N-terminal domain forfunction. Mol. Plant Microbe Interact. 20: 346-357. DOI: [[https://doi.org/10.1094/MPMI-20-4-0346|10.1094/MPMI-20-4-0346]]

Popov G, Fraiture M, Brunner F, Sessa G (2016). Multiple //Xanthomonas euvesicatoria// type III effectors inhibit flg22-triggered immunity. Mol. Plant Microbe Interact. 29: 651-660. DOI: [[https://doi.org/10.1094/MPMI-07-16-0137-R|10.1094/MPMI-07-16-0137-R]]

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|0.1094/MPMI-09-10-0196]]

Sonnewald S, Priller JP, Schuster J, Glickmann E, Hajirezaei MR, Siebig S, Mudgett MB, Sonnewald U (2012). Regulation of cell wall-bound invertase in pepper leaves by //Xanthomonas campestris// pv. //vesicatoria// type three effectors. PLoS One 7: e51763. DOI: [[https://dx.doi.org/10.1371/journal.pone.0051763|10.1371/journal.pone.0051763]]

Thieme F, Koebnik R, Bekel T, Berger C, Boch J, Büttner D, Caldana C, Gaigalat L, Goesmann A, Kay S, Kirchner O, Lanz C, Linke B, McHardy AC, Meyer F, Mittenhuber G, Nies DH, Niesbach-Klösgen U, Patschkowski T, Rückert C, Rupp O, Schneiker S, Schuster SC, Vorhölter F, Weber E, Pühler A, Bonas U, Bartels D, Kaiser O (2005). Insights into genome plasticity and pathogenicity of the plant pathogenic bacterium //Xanthomonas campestris// pv. vesicatoria revealed by the complete genome sequence. J. Bacteriol. 187: 7254-7266. DOI: [[https://doi.org/10.1128/JB.187.21.7254-7266.2005|10.1128/JB.187.21.7254-7266.2005]]

Thieme F, Szczesny R, Urban A, Kirchner O, Hause G, Bonas U (2007). New type III effectors from //Xanthomonas campestris// pv. vesicatoria trigger plant reactions dependent on a conserved N-myristoylation motif. Mol Plant Microbe Interact. 20: 1250-1261. DOI: [[https://doi.org/10.1094/MPMI-20-10-1250|10.1094/MPMI-20-10-1250]]

===== Further reading =====

He YQ, Zhang L, Jiang BL, Zhang ZC, Xu RQ, Tang DJ, Qin J, Jiang W, Zhang X, Liao J, Cao JR, Zhang SS, Wei ML, Liang XX, Lu GT, Feng JX, Chen B, Cheng J, Tang JL (2007). Comparative and functional genomics reveals genetic diversity and determinants of host specificity among reference strains and a large collection of Chinese isolates of the phytopathogen //Xanthomonas campestris//  pv. //campestris//. Genome Biol. 8: R218. DOI: [[https://doi.org/10.1186/gb-2007-8-10-r218|10.1186/gb-2007-8-10-r218]]

===== Acknowledgements =====

This fact sheet is based upon work from COST Action CA16107 EuroXanth, supported by COST (European Cooperation in Science and Technology).