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Author: Jaime Cubero
Internal reviewer: Eran Bosis
Expert reviewer: Adriana Bernal

Class: XopE
Family: XopE4
Prototype: XAUC_31730 (Xanthomonas fuscans pv. aurantifolii)
GenBank ID: EFF46466.1 (388 aa - likely too long)
RefSeq ID: WP_244170787.1 (367 aa)
3D structure: unknown

Biological function

How discovered?

XopE4 was first identified by sequence homology searches (Moreira et al., 2010).

(Experimental) evidence for being a T3E

Homology to other XopE effectors.




The gene sequence of xopE4 is similar to XopE2 (avrXacE3), but due to its low amino acid sequence identity (31%) was considered a different effector that can discriminate between X. citri and X. fuscans pv. aurantifolii strains, both causing citrus bacterial canker (Moreira et al., 2010; Dalio et al., 2017). Disease symptoms caused by Xanthomonas axonopodis pv. manihotis mutant strains deleted for xopE4 are similar to those caused by the wild-type strain. Moreover, using heterologous systems XopE4 was unable to suppress (PAMP)-triggered immunity (PTI) but showed weak ability to suppress effector-triggered immunity (ETI) (Medina et al., 2018).


As XopE4 does not have a predicted myristoylation site, suggesting that it may not be targeted to the cell membrane as the other XopE family member (Moreira et al., 2010).

Enzymatic function

XopE4 belongs to the HopX effector family, which are part of the transglutaminase superfamily (Nichmuk et al., 2007).

Interaction partners

Not known.


In xanthomonads

Yes (e.g., X. axonopodis).

XopE4 is also present in X. fragariae (Vandroemme et al., 2013) and it is not very conserved among X. perforans strains (Schwartz et al., 2015).

In other plant pathogens/symbionts



Dalio RJD, Magalhães DM, Rodrigues CM, Arena GD, Oliveira TS, Souza-Neto RR, Picchi SC, Martins PMM, Santos PJC, Maximo HJ, Pacheco IS, De Souza AA, Machado MA (2017). PAMPs, PRRs, effectors and R-genes associated with citrus-pathogen interactions. Ann. Bot. 119: 749-774. DOI: 10.1093/aob/mcw238.

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: 10.1111/mpp.12545.

Moreira LM, Almeida NF Jr, Potnis N, Digiampietri LA, Adi SS, Bortolossi JC, da Silva AC, da Silva AM, de Moraes FE, de Oliveira JC, de Souza RF, Facincani AP, Ferraz AL, Ferro MI, Furlan LR, Gimenez DF, Jones JB, Kitajima EW, Laia ML, Leite RP Jr, Nishiyama MY, Rodrigues Neto J, Nociti LA, Norman DJ, Ostroski EH, Pereira HA Jr, Staskawicz BJ, Tezza RI, Ferro JA, Vinatzer BA, Setubal JC. (2010). Novel insights into the genomic basis of citrus canker based on the genome sequences of two strains of Xanthomonas fuscans subsp. aurantifolii. BMC Genomics 11: 238. DOI: 10.1186/1471-2164-11-238.

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: 10.1094/MPMI-20-4-0346.

Schwartz, A. R., Potnis, N., Timilsina, S., Wilson, M., Patané, J., Martins Jr, J., & Vallad, G. E. (2015). Phylogenomics of Xanthomonas field strains infecting pepper and tomato reveals diversity in effector repertoires and identifies determinants of host specificity. Front. Microbiol. 6: 535. DOI: 10.3389/fmicb.2015.00535

Vandroemme, J., Cottyn, B., Baeyen, S., De Vos, P., & Maes, M. (2013). Draft genome sequence of Xanthomonas fragariae reveals reductive evolution and distinct virulence-related gene content. BMC Genomics 14: 829. DOI: 10.1186/1471-2164-14-829

bacteria/t3e/xope4.txt · Last modified: 2023/05/24 08:28 by rkoebnik