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Author: Harrold van den Burg
Internal reviewer: Jakub Pečenka
Expert reviewer: Zoe Dubrow

Class: XopO
Family: XopO
Prototype: XopO (Xanthomonas euvesicatoria pv. euvesicatoria, ex Xanthomonas campestris pv. vesicatoria; strain 85-10)
GenBank ID: AAV74207.1 (220 aa)
RefSeq ID: WP_011346566.1 (211 aa)
3D structure: Unknown

Biological function

How discovered?

XopO was identified in a genetic screen, using a Tn5-based transposon construct harboring the coding sequence for the HR-inducing domain of AvrBs2, but devoid of the effectors' T3SS signal, that was randomly inserted into the genome of X. campestris pv. vesicatoria (Xcv)strain 85-10. The XopO::AvrBs2 fusion protein triggered a Bs2-dependent hypersensitive response (HR) in pepper leaves (Roden et al., 2004).

(Experimental) evidence for being a T3E

Type III-dependent secretion was confirmed using a calmodulin-dependent adenylate cyclase reporter assay, with a ΔhrpF mutant strain serving as negative control (Roden et al., 2004).


XopO was found to be regulated by HrpG using HrpG* (Roden et al., 2004). XopO contains a PIP box sequence 31bp upstream of the -10 promoter motif (Koebnik et al., 2006).


  • Roden et al. did not find significant growth defects of a Xcv ΔxopO mutant in susceptible pepper and tomato leaves (Roden et al., 2004).
  • XopO from Xcv 85-10 inhibits cell death in N. benthamiana (Teper et al., 2015).
  • XopO suppresses X. euvesicatoria-induced chlorosis in leaves of susceptible tomato (Teper et al., 2015).
  • XopO failed to inhibit expression of the reporter gene FRK1 in response to application of a PAMP, i.e. flg22 peptide (Popov et al., 2016).
  • Based on whole genome sequences of X. euvesicatoria strains, it was concluded that the xopO gene has suffered from mutational inactivation by at least four different events, suggesting that selection pressure favors loss of xopO function in this pathogen (Barak et al., 2016).



Enzymatic function


Interaction partners

XopO was shown to interact with tomato 14-3-3 (TFT) proteins (Dubrow et al., 2018).


In xanthomonads

Yes, in some xanthomonads (e.g., X. euvesicatoria, X. oryzae) (Lang et al., 2019). XopO is a differential T3E gene between Xoo and Xoc (Hajri et al., 2012).

In other plant pathogens/symbionts

Yes, e.g. homologs (AvrRps4 and HopK1) in Pseudomonas syringae (Li et al., 2014).


Barak JD, Vancheva T, Lefeuvre P, Jones JB, Timilsina S, Minsavage GV, Vallad GE, Koebnik R (2016) Whole-genome sequences of Xanthomonas euvesicatoria strains clarify taxonomy and reveal a stepwise erosion of type 3 effectors. Front Plant Sci. 7: 1805. DOI: 10.3389/fpls.2016.01805

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: 10.1094/MPMI-02-18-0048-R

Hajri A, Brin C, Zhao S, David P, Feng JX, Koebnik R, Szurek B, Verdier V, Boureau T, Poussier S (2012). Multilocus sequence analysis and type III effector repertoire mining provide new insights into the evolutionary history and virulence of Xanthomonas oryzae. Mol. Plant Pathol. 13: 288-302. DOI: 10.1111/j.1364-3703.2011.00745.x

Koebnik R, Krüger A, Thieme F, Urban A, Bonas U (2006). Specific binding of the Xanthomonas campestris pv. vesicatoria AraC-type transcriptional activator HrpX to plant-inducible promoter boxes. J. Bacteriol. 188: 7652-7660. DOI: 10.1128/JB.00795-06

Lang JM, Pérez-Quintero AL, Koebnik R, DuCharme E, Sarra S, Doucoure H, Keita I, Ziegle J, Jacobs JM, Oliva R, Koita O, Szurek B, Verdier V, Leach JE (2019). A pathovar of Xanthomonas oryzae infecting wild grasses provides insight into the evolution of pathogenicity in rice agroecosystems. Front. Plant Sci. 10: 507. DOI: 10.3389/fpls.2019.00507

Li G, Froehlich JE, Elowsky C, Msanne J, Ostosh AC, Zhang C, Awada T, Alfano JR, (2014). Distinct Pseudomonas type-III effectors use a cleavable transit peptide to target chloroplasts. Plant J. 77: 310–321. DOI: 10.1111/tpj.12396

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: 10.1094/MPMI-07-16-0137-R

Roden JA, Belt B, Ross JB, Tachibana T, Vargas J, Mudgett MB (2004). A genetic screen to isolate type III effectors translocated into pepper cells during Xanthomonas infection. Proc. Natl. Acad. Sci. USA 101: 16624-16629. DOI: 10.1073/pnas.0407383101

Sohn KH, Zhang Y, Jones JD (2009). The Pseudomonas syringae effector protein, AvrRPS4, requires in planta processing and the KRVY domain to function. Plant J. 57: 1079-1091. DOI: 10.1111/j.1365-313X.2008.03751.x FIXME Information needs to be added to the profile.

Teper D, Sunitha S, Martin GB, Sessa G (2015). Five Xanthomonas type III effectors suppress cell death induced by components of immunity-associated MAP kinase cascades. Plant Signal. Behav. 10: e1064573. DOI: 10.1080/15592324.2015.1064573

bacteria/t3e/xopo.txt · Last modified: 2023/05/24 08:23 by rkoebnik