Author: Ralf Koebnik
Internal reviewer: Anna Passelergue

Class: XopBA
Family: XopBA
Prototype: XopBA_Xee66b (Xanthomonas euvesicatoria pv. euvesicatoria; strain 66b)
RefSeq ID: WP_227478587.1 (500 aa)
3D structure: Unknown

XopBA_Xee66b was discovered by homology to HopW/HopPmaA in Pseudomonas syringae (70% aa sequence identity) and EspW in Escherichia coli (30% aa sequence identity) (Stavrinides & Guttman, 2004; Sandu et al., 2017).

The homolog in Xanthomonas graminis pv. arrhenatheri strain LMG 727 with 77% sequence identity (KM317_RS05475), XopBA_XgaLMG727, was discovered as an ORF that is encoded downstream of a PIP box and a properly spaced ‐10 promoter motif (TTCGB‐N₁₅ ‐TTCGB‐N_30–32 ‐YANNNT) (Passelergue, 2025)

XopBA_XgaLMG727 was shown to have a functional type III secretion signal using a reporter fusion with AvrBs1 (Zhao et al., 2013; Passelergue, 2025).

The presence of a PIP box and a properly spaced ‐10 promoter motif (TTCGB‐N₁₅ ‐TTCGB‐N_30–32 ‐YANNNT) suggests that the xopBA_{Xga LMG727} gene is under control of HrpG and HrpX (Wengelnik & Bonas, 1996; Wengelnik et al., 1996; Koebnik et al., 2006).

Ectopic expression of the distant homolog in E. coli, EspW, results in formation of unique membrane protrusions (Sandu et al., 2017)

The distant homolog in E. coli, EspW, and Kif15 colocalized in cotransfected cells, while ectopically expressed Kif15 localized to the actin pedestals following EHEC infection (Sandu et al., 2017).

The distant homolog in E. coli, EspW, modulates actin dynamics in a Rac1-dependent manner (Sandu et al., 2017).

The distant homolog in E. coli, EspW, was found to interact with the motor protein Kif15 in a yeast two-hybrid screen (Sandu et al., 2017).

Yes (e.g., X. euvesicatoria, X. axonopodis, X. campestris, X. vasicola, X. citri, X. phaseoli, X. arboricola, X. graminis, X. transclucens, X. hortorum, X. populi, X. bromi, X. nasturtii, X. hyacinthi)

Yes (e.g., Pseudomonas spp., Erwinia spp., Robbsia andropogonis, Acidovorax/Paracidovorax spp.)

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

Passelergue A (2025). Discovery of eight type III effector genes harboring the PIP box in clade-I xanthomonads. Master's thesis, Université de Montpellier, France.

Sandu P, Crepin VF, Drechsler H, McAinsh AD, Frankel G, Berger CN (2017). The enterohemorrhagic Escherichia coli effector EspW triggers actin remodeling in a Rac1-dependent manner. Infect. Immun. 85: e00244-17. doi: 10.1128/IAI.00244-17

Stavrinides J, Guttman DS (2004). Nucleotide sequence and evolution of the five-plasmid complement of the phytopathogen Pseudomonas syringae pv. maculicola ES4326. J. Bacteriol. 186: 5101-5115. doi: 10.1128/JB.186.15.5101-5115.2004

Wengelnik K, Bonas U (1996). HrpXv, an AraC-type regulator, activates expression of five of the six loci in the hrp cluster of Xanthomonas campestris pv. vesicatoria. J. Bacteriol. 178: 3462-3469. DOI: 10.1128/jb.178.12.3462-3469.1996

Wengelnik K, Van den Ackerveken G, Bonas U (1996). HrpG, a key hrp regulatory protein of Xanthomonas campestris pv. vesicatoria is homologous to two-component response regulators. Mol. Plant Microbe Interact. 9: 704-712. DOI: 10.1094/mpmi-9-0704

Zhao S, Mo WL, Wu F, Tang W, Tang JL, Szurek B, Verdier V, Koebnik R, Feng JX (2013). Identification of non-TAL effectors in Xanthomonas oryzae pv. oryzae Chinese strain 13751 and analysis of their role in the bacterial virulence. World J. Microbiol. Biotechnol. 29: 733-744. DOI: 10.1007/s11274-012-1229-5

This fact sheet is based upon work from COST Action CA16107 EuroXanth, supported by COST (European Cooperation in Science and Technology).