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). === Phenotypes === Ectopic expression of the distant homolog in E. coli, EspW, results in formation of unique membrane protrusions (Sandu et al., 2017) === Localization === 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). === Enzymatic function === The distant homolog in E. coli, EspW, modulates actin dynamics in a Rac1-dependent manner (Sandu et al., 2017). === Interaction partners === 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). ===== Conservation ===== === In xanthomonads === 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) === In other plant pathogens/symbionts === Yes (e.g., Pseudomonas spp., Erwinia spp., Robbsia andropogonis, Acidovorax/Paracidovorax spp.) ===== References ===== 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 ===== Acknowledgements ===== This fact sheet is based upon work from COST Action CA16107 EuroXanth, supported by COST (European Cooperation in Science and Technology).