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Author: Jose Gadea
Internal reviewer: Saul Burdman
Expert reviewer: WANTED!

Class: XopAQ
Family: XopAQ
Prototype: XGA_2091 (Xanthomonas hortorum pv. gardneri, ex. Xanthomonas gardneri; strain 101 = ATCC 19865)
GenBank ID: EGD19295.1 (95 aa)
RefSeq ID: WP_233366621.1 (93 aa)
3D structure: Unknown

Biological function

How discovered?

XopAQ was predicted to be a type 3 effector based on homology to Rip6/11, a type 3 effector from Ralstonia solanacearum (Potnis et al., 2011).

(Experimental) evidence for being a T3E

A functional screen to isolate Ralstonia solanacearum genes encoding proteins translocated into plant cells revealed that the genes rip6 and rip11 encode two new translocated proteins. XopAQ is 60% identical to Rip6 and Rip11. BlastP alignment between XopAQ and Rip6 indicates that the homology is spanned along the whole protein, including the N-terminal part, suggesting that the functional motif that drives translocation in Rip6 is conserved in XopAQ. Translocation assays using a strain deleted in the hpaB gene of Ralstonia indicates that Rip6 and Rip11 requires HpaB for their effective translocation into plant cells via the Hrp-T3SS (Mukaihara et al., 2010). However, to the best of our knowledge, no functional translocation assay has been performed for Xanthomonas XopAQ.


The coding sequence of xopAQ from X. gardneri was found 68 bps downstream of a perfect PIP box (Potnis et al., 2011). Similarly, in X. arboricola the xopAQ gene has a putative plant-inducible promoter box (PIP-BOX) sequence, 67 bp upstream of the TATA box (Garita-Cambronero, 2016). The xopAQX. citri pv. citri 306 and X. citri pv. citri Aw 12879 (restricted to Mexican lime) were grown in XVM2 (a medium that is known to induce expression of hrp genes and several effector genes in Xanthomonas sp.), as compared with nutrient broth (NB). However, no differential expression was observed for this gene among these two strains (Jalan et al., 2013).




CSS-Palm suite reveals potential myristoylation/palmitoylation motifs for XopAQ, suggesting that the protein could be targeted to the cytoplasmic membrane (Barak et al., 2016). This targeting is facilitated by a simple sequence motif at the N terminus of the polypeptide chain.

Enzymatic function

Unknown. No known motifs are found in the Rip6 and Rip11 proteins of Ralstonia (Mukaihara et al., 2010). No motifs are found in the X. gardneri protein neither (Prosite analysis).

Interaction partners



In xanthomonads

Yes. The effector is widely present in the most agressive citrus canker-causing X.citri A strains but also in the AW strain (narrow host range) (Escalon et al., 2013; Garita-Cambronero et al., 2019), and also in the milder X. fuscans B strain, but not in the X. fuscans C strain, whic is restricted to C. aurantifoli (Dalio et al., 2017). Present in Xanthomonas gardneri but not in some strains of X. perforans nor X. euvesicatoria strains affecting pepper and tomato (Potnis et al., 2011; Schwartz et al., 2015; Vancheva et al., 2015; Jibrin et al., 2018). Two paralogs of XopAQ are present in strains 66b and LMG 918 of X. euvesicatoria, but not present in other LMG strains, 83b, 85-10, or X. euvesicatoria pv. rosa (Barak et al., 2016). Present in pathogenic but not in non-pathogenic X. arboricola pv. pruni (Garita-Cambronero et al., 2016, 2019). Absent in the related X. juglandis or X. corylina (Garita-Cambronero et al., 2018). Also present in X. citri pv. viticola (Schwartz et al., 2015) and other X. citri pathovars (blastp analysis). X. phaseolis and X. populi, among others, posess putative genes encoding proteins with moderate homology to XopAQ based on Blastp analysis.

In other plant pathogens/symbionts

Yes (Ralstonia).


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

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

Escalon A, Javegny S, Vernière C, Noël LD, Vital K, Poussier S, Hajri A, Boureau T, Pruvost O, Arlat M, Gagnevin L (2013). Variations in type III effector repertoires, pathological phenotypes and host range of Xanthomonas citri pv. citri pathotypes. Mol. Plant. Pathol. 14: 483-96. DOI: 10.1111/mpp.12019

Ferreira MASV, Bonneau S, Briand M, Cesbron S, Portier P, Darrasse A, Gama MAS, Barbosa MAG, Mariano RLR, Souza EB, Jacques MA (2009). Xanthomonas citri pv. viticola affecting grapevine in Brazil: Emergence of a successful monomorphic pathogen. Front. Plant Sci. 10: 489. DOI: 10.3389/fpls.2019.00489

Garita-Cambronero J (2016). Genómica comparativa de cepas de Xanthomonas arborícola asociadas a Prunus ssp. Caracterización de los procesos de infección de la mancha bacteriana de frutales de hueso y almendro. Doctoral Thesis, Universidad Politécnica de Madrid, Spain. PDF:

Garita-Cambronero J, Palacio-Bielsa A, Cubero J (2018). Xanthomonas arboricola pv. pruni, causal agent of bacterial spot of stone fruits and almond: its genomic and phenotypic characteristics in the X. arboricola species context. Mol. Plant Pathol. 19: 2053-2065. DOI: 10.1111/mpp.12679

Garita-Cambronero J, Palacio-Bielsa A, López MM, Cubero J (2016). Comparative genomic and phenotypic characterization of pathogenic and non-pathogenic strains of Xanthomonas arboricola reveals insights into the infection process of bacterial spot disease of stone fruits. PLoS One 11: e0161977. DOI: 10.1371/journal.pone.0161977

Garita-Cambronero J, Sena-Vélez M, Ferragud E, Sabuquillo P, Redondo C, Cubero J (2019). Xanthomonas citri subsp. citri and Xanthomonas arboricola pv. pruni: Comparative analysis of two pathogens producing similar symptoms in different host plants. PLoS One 14: e0219797. DOI: 10.1371/journal.pone.0219797

Jalan N, Kumar D, Andrade MO, Yu F, Jones JB, Graham JH, White FF, Setubal JC, Wang N (2013). Comparative genomic and transcriptome analyses of pathotypes of Xanthomonas citri subsp. citri provide insights into mechanisms of bacterial virulence and host range. BMC Genomics 14: 551. DOI: 10.1186/1471-2164-14-551

Jibrin MO, Potnis N, Timilsina S, Minsavage GV, Vallad GE, Roberts PD, Jones JB, Goss EM (2018). Genomic inference of recombination-mediated evolution in Xanthomonas euvesicatoria and X. perforans. Appl. Environ. Microbiol. 84: e00136-18. DOI: 10.1128/AEM.00136-18

Mukaihara T, Tamura N, Iwabuchi M (2010). Genome-wide identification of a large repertoire of Ralstonia solanacearum type III effector proteins by a new functional screen. Mol. Plant Microbe Interact. 23: 251-262. 10.1094/MPMI-23-3-0251

Potnis N, Krasileva K, Chow V, Almeida NF, Patil PB, Ryan RP, Sharlach M, Behlau F, Dow JM, Momol M, White FF, Preston JF, Vinatzer BA, Koebnik R, Setubal JC, Norman DJ, Staskawicz BJ, Jones JB (2011). Comparative genomics reveals diversity among xanthomonads infecting tomato and pepper. BMC Genomics 12: 146. DOI: 10.1186/1471-2164-12-146

Schwartz AR, Potnis N, Timilsina S, Wilson M, Patané J, Martins J Jr, Minsavage GV, Dahlbeck D, Akhunova A, Almeida N, Vallad GE, Barak JD, White FF, Miller SA, Ritchie D, Goss E, Bart RS, Setubal JC, Jones JB, Staskawicz BJ (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

Vancheva T, Lefeuvre P, Bogatzevska N, Moncheva P, Koebnik R (2015). Draf genome sequences of two Xanthomonas euvesicatoria strains from the Balkan Peninsula. Genome Announc. 3: e01528-14. DOI: 10.1128/genomeA.01528-14

bacteria/t3e/xopaq.txt · Last modified: 2023/10/03 07:55 by rkoebnik