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Author: Steven J. Roberts
Internal reviewer: Christian Vernière
Expert reviewer: WANTED!

Class: XopAH
Family: XopAH
Prototype: AvrXccC (Xanthomonas campestris pv. campestris; strain 8004)
GenBank ID: ABQ10636.1 (440 aa)
RefSeq ID: WP_011037263.1 (331 aa, perhaps 109 aa too short since the 440-aa version would include a typical N-terminal palmitoylation signal, MGLC)
Synonym: AvrXccC (Xanthomonas campestris pv. campestris), AvrXccFM (Xanthomonas campestris pv. campestris) (Castañeda et al., 2005)
3D structure: Unknown

Biological function

How discovered?

AvrXccC was described during a genome comparison analysis between Xanthomonas citri pv. citri and X. campestris pv. campestris Xcc strain ATCC 33913 = NCPPB 528 (Da Silva et al., 2002) and in a search of annotated genome (Castenada et al., 2005).

(Experimental) evidence for being a T3E

Secreted XopAH (AvrXccC) proteins were detected in culture fluid from Xcc 8004 and hrcV mutant complemented strains but not from the hrcV mutant (Wang et al., 2007). Insertion and deletion mutants affecting the locus (Xcc2109) in the type strain (Xcc 528) resulted in loss of virulence on the host Florida Broad Leaf Mustard (Castañeda et al., 2005).


Promoter activity assays showed that the expression of XopAH (avrXccC) is hrpG/hrpX-dependent (Wang et al., 2007).


This effector is required for full virulence in the susceptible host cabbage (Brassica oleracea) (Wang et al., 2007) and results in avirulence in the resistant host mustard (Brassica napiformis) (Castaneda et al., 2005; He et al., 2007; Wang et al., 2007). The intact AvrB-AvrC domain of AvrXccC8004 is essential and sufficient to elicit defense responses in an Arabidopsis resistant ecotype (Col-0) (Ho et al., 2013).

In the interaction Arabidopsis / Xcc strain 8004, AvrXccC8004 not only presented its avirulence activity to trigger plant defense response but also possessed its virulence activity to manipulate the component involved in the ABA signalling pathway leading to an increase of ABA concentrations (Ho et al., 2013).


XopAH (AvrXccC) is anchored to the plant plasma membrane, and the N‐terminal myristoylation site (amino acids 2–7: GLcaSK) is essential for its localization (Wang et al., 2007).

Enzymatic function

XopAH has a Fido/AvrB domain derived from the fic (cyclic adenosine monophosphate (cAMP)-induced filamentation and doc (death on curing) domains (Kinch et al., 2009). Structural comparisons resulted in the inclusion of similar segments of the T3 effector AvrB from Pseudomonas syringae species (Kinch et al., 2009; White et al., 2009). T3 effectors in the XopAH group could trans-AMPylate plant host proteins. AMPylation represents a posttranslational modification used to stably modify proteins with AMP (Kinch et al., 2009).

Interaction partners

Not known ?


In xanthomonads

In Xanthomonas campestris pv. campestris. XopAH is also present in X. arboricola pv. juglandis within strains causing Walnut Blight but is absent from the strains causing vertical oozing canker (Cesbron et al., 2015).

In other plant pathogens/symbionts

Yes (AvrB Pseudomonas savastanoi, Pseudomonas syringae) (Lee et al., 2004; Desveaux et al., 2007)


Castañeda A, Reddy JD, El-Yacoubi B, Gabriel DW (2005). Mutagenesis of all eight avr genes in Xanthomonas campestris pv. campestris had no detected effect on pathogenicity, but one avr gene affected race specificity. Mol. Plant Microbe Interact. 18: 1306-1317. DOI: 10.1094/MPMI-18-1306

Cesbron S, Briand M, Essakhi S, Gironde S, Boureau T, Manceau C, Fischer-Le Saux M, Jacques MA (2015). Comparative genomics of pathogenic and nonpathogenic strains of Xanthomonas arboricola unveil molecular and evolutionary events linked to pathoadaptation. Front. Plant Sci. 6: 1126. DOI: 10.3389/fpls.2015.01126

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 Santos M, 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: 10.1038/417459a

Desveaux D, Singer AU, Wu AJ, McNulty BC, Musselwhite L, Nimchuk Z, Sondek J, Dangl JL (2007). Type III effector activation via nucleotide binding, phosphorylation, and host target interaction. PLoS Pathog. 3: e48. DOI: 10.1371/journal.ppat.0030048. Erratum in: PLoS Pathog. (2007) 3: e90.

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: 10.1186/gb-2007-8-10-r218

Ho YP, Tan CM, Li MY, Lin H, Deng WL, Yang JY (2013). The AvrB_AvrC Domain of AvrXccC of Xanthomonas campestris pv. campestris is required to elicit plant defense responses and manipulate ABA homeostasis. Mol. Plant Microbe Interact. 26: 419-430. DOI: 10.1094/mpmi-06-12-0164-r

Kinch LN, Yarbrough ML, Orth K, Grishin NV (2009). Fido, a novel AMPylation domain common to Fic, Doc, and AvrB. PLoS One 4: e5818. DOI: 10.1371/journal.pone.0005818

Lee CC, Wood MD, Ng K, Andersen CB, Liu Y, Luginbühl P, Spraggon G, Katagiri F (2004). Crystal structure of the type III effector AvrB from Pseudomonas syringae. Structure 12: 487-494. DOI: 10.1016/j.str.2004.02.013

Qian W, Jia Y, Ren SX, He Y Q, Feng JX, Lu LF, Sun Q, Ying G, Tang DJ, Tang H, Wu W, Hao P, Wang L, Jiang BL, Zeng S, Gu WY, Lu G, Rong L, Tian Y, Yao Z, Fu G, Chen B, Fang R, Qiang B, Chen Z, Zhao GP, Tang JL, He C (2005). Comparative and functional genomic analyses of the pathogenicity of phytopathogen Xanthomonas campestris pv. campestris. Genome Res. 15: 757-767. DOI: 10.1101/gr.3378705

Wang L, Tang X, He C (2007). The bifunctional effector AvrXccC of Xanthomonas campestris pv. campestris requires plasma membrane-anchoring for host recognition. Mol. Plant Pathol. 8: 491-501. DOI: 10.1111/j.1364-3703.2007.00409.x

White FF, Potnis N, Jones JB, Koebnik R (2009). The type III effectors of Xanthomonas. Mol. Plant Pathol. 10: 749-766. DOI: 10.1111/j.1364-3703.2009.00590.x

bacteria/t3e/xopah.txt · Last modified: 2023/10/03 07:52 by rkoebnik