====== The Type III Effector XopBA from //Xanthomonas// ======

Author: [[https://www.researchgate.net/profile/Ralf-Koebnik|Ralf Koebnik]]\\
Internal reviewer: Anna Passelergue

Class: XopBA\\
Family: XopBA\\
Prototype: XopBA<sub>//Xee//66b</sub> (//Xanthomonas euvesicatoria// pv. //euvesicatoria//; strain 66b)\\
RefSeq ID: [[https://www.ncbi.nlm.nih.gov/protein/WP_227478587.1|WP_227478587.1]] (500 aa)\\
3D structure: Unknown

===== Biological function =====

=== How discovered? ===

XopBA<sub>//Xee//66b</sub> 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<sub>//Xga//LMG727</sub>, was discovered as an ORF that is encoded downstream of a PIP box and a properly spaced ‐10 promoter motif (TTCGB‐N<sub>15</sub> ‐TTCGB‐N<sub>30–32</sub> ‐YANNNT) (Passelergue, 2025)
=== (Experimental) evidence for being a T3E ===

XopBA<sub>//Xga//LMG727</sub> was shown to have a functional type III secretion signal using a reporter fusion with AvrBs1 (Zhao //et al.//, 2013; Passelergue, 2025).
=== Regulation ===

The presence of a PIP box and a properly spaced ‐10 promoter motif (TTCGB‐N<sub>15</sub> ‐TTCGB‐N<sub>30–32</sub> ‐YANNNT) suggests that the //xopBA<sub>Xga</sub> // <sub>LMG727</sub> //<sup> </sup>  // 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: [[https://doi.org/10.1128/JB.00795-06|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: [[https://doi.org/10.1128/IAI.00244-17|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: [[https://doi.org/10.1128/JB.186.15.5101-5115.2004|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: [[https://doi.org/10.1128/jb.178.12.3462-3469.1996|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: [[https://doi.org/10.1094/mpmi-9-0704|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: [[https://doi.org/10.1007/s11274-012-1229-5|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).