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Author: Tamás Kovács
Internal reviewer: Guido Sessa
Expert reviewer: WANTED!

Class: XopAF
Family: XopAF1, XopAF2
Prototype: AvrXv3 (Xanthomonas euvesicatoria pv. perforans; strain T3)
GenBank ID (XopAF1): AAG18480.1 (218 aa)
RefSeq ID (XopAF1): WP_008577605.1 (218 aa)
RefSeq ID (XopAF2): WP_227479740.1 (286 aa)
Synonym: AvrXv3
3D structure: Unknown

Biological function

How discovered?

AvrXv3 was discovered by genetic screen and cloning and sequencing its encoding gene from Xanthomonas euvesicatoria pv. perforans (Minsavage et al., 1996).

(Experimental) evidence for being a T3E

Signal sequence analysis (Roden et al., 2004).


Induced; PIP box (Astua-Monge et al., 2000).


Expression studies with a fusion of this gene and uidA indicated that avrXv3 is plant inducible and controlled by the hypersensitivity and pathogenicity (hrp) regulatory system. Mutational analysis and transcription activation assays revealed that AvrXv3 has transcription activation activity in yeast, and that the putative domain responsible for that activity is located at the C terminus of the AvrXv3 protein. Agrobacterium tumefaciens-mediated transient expression confirmed the direct role of AvrXv3 in eliciting the hypersensitive response (HR) in tomato NIL 216 and supported the hypothesis that Avr proteins must be present inside the plant host cell to trigger the HR (Astua-Monge et al., 2000). Tomato genes differential expressed during the resistance response triggered by AvrXv3 recognition were identified by microarray analysis (Balaji et al., 2007).


Inside the plant host cell, no further details are available.

Enzymatic function

Unknown. The orthologue HopAF1 is a deaminase, inhibits ethylene biosynthesis (Washington et al., 2016).

Interaction partners

Tomato RxvT3 resistance protein (has not been identified yet).


In xanthomonads

Yes (e.g., X. alfalfae, X. citri, X. translucens) (Washington et al., 2016).

In other plant pathogens/symbionts

Yes (Pseudomonas, Acidovorax, Ralstonia spp.) (Washington et al., 2016).


Astua-Monge G, Minsavage VG, Stall ER, Davis JM, Bonas U, Jones BJ (2000). Resistance of tomato and pepper to T3 strains of Xanthomonas campestris pv. vesicatoria is specified by a plant-inducible avirulence gene. Mol. Plant Microbe Interact. 13: 911-921. DOI: 10.1094/MPMI.2000.13.9.911

Balaji V, Gibly A, Debbie P, Sessa G (2007). Transcriptional analysis of the tomato resistance response triggered by recognition of the Xanthomonas type III effector AvrXv3. Funct. Integr. Genomics 7: 305-3016. DOI:

Minsavage GV, Jones JB, Stall RE (1996). Cloning and sequencing of an avirulence gene (avrRxv3) isolated from Xanthomonas campestris pv. vesicatoria tomato race 3. Phytopathology 86: S15.

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

Washington EJ, Mukhtar MS, Finkel MO, Wan L, Banfield JM, Kieber JJ, Dangl LJ (2016). Pseudomonas syringae type III effector HopAF1 suppresses plant immunity by targeting methionine recycling to block ethylene induction. Proc. Natl. Acad. Sci. USA. 113: E3577-E3586. DOI: 10.1073/pnas.1606322113

Further reading

Gibly A, Bonshtien A, Balaji V, Debbie P, Martin GB, Sessa G (2004). Identification and expression profiling of tomato genes differentially regulated during a resistance response to Xanthomonas campestris pv. vesicatoria. Mol. Plant Microbe Interact. 17: 1212-1222. DOI: 10.1094/MPMI.2004.17.11.1212

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

Timilsina S, Abrahamian P, Potnis N, Minsavage GV, White FF, Staskawicz BJ, Jones JB, Vallad GE, Goss EM (2016). Analysis of sequenced genomes of Xanthomonas perforans identifies candidate targets for resistance breeding in tomato. Phytopathology 106: 1097-1104. DOI: 10.1094/PHYTO-03-16-0119-FI

bacteria/t3e/xopaf.txt · Last modified: 2023/10/03 07:51 by rkoebnik