Author: Ralf Koebnik
Internal reviewer: Anna Passelergue

Class: XopW
Families: XopW1, XopW2, XopW3, XopW4, XopW5
Prototype: XOO0037 (XopW1) (Xanthomonas oryzae pv. oryzae; strain T7174), G4Q83_RS22690 (XopW2) (Xanthomonas theicola; strain CFBP 4691), AB8814_02550 (XopW3) (Xanthomonas hydrangeae; strain NCPPB 4692), LYZ81_10440 (XopW4) (Xanthomonas hortorum; strain BP5178), C8F00_2046 (XopW5) (Xanthomonas vasicola; strain BLS185)
GenBank ID: XopW1BAE66792.1 (204 aa), XopW2QNH27166.1 (85 aa), XopW3XDZ21859.1 (196 aa), XopW4MCE4362839.1 (227 aa), XopW5TCK49608.1 (228 aa)
RefSeq ID: XopW1WP_228329674.1 (203 aa), XopW2WP_211288317.1 (176 aa), XopW3WP_205393482.1 (196 aa), XopW4WP_233380913.1 (227 aa), XopW5WP_230597584.1 (228 aa)
3D structure: Unknown

XopW1 was discovered via genome-wide screening for effector candidates in X. oryzae pv. oryzae (Xoo) strain MAFF 311018 in accordance with three criteria: i) ORF encoding proteins homologous to effectors of P. syringae strains and X. campestris pv. vesicatoria, ii) HrpX regulons preceded by two cis elements (Plant Induced Promoter, PIP; and -10 box-like motif) or iii) proteins with an N-terminal amino acid composition similar to known effectors (more than 10% of Ser in the first 50 amino aa, no Asp or Glu residues in the first 12 aa, and an aliphatic amino acid or Pro at the third or fourth position) (Furutani et al., 2009).

XopW2 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).

TT3S-dependent translocation of XopW1 has been shown by a calmodulin-dependent adenylate cyclase reporter assay (Furutani et al., 2009). XopW1 and XopW2 were confirmed/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 xopW2 gene is under control of HrpG and HrpX (Wengelnik & Bonas, 1996; Wengelnik et al., 1996; Koebnik et al., 2006).

Unknown.

Unknown.

Unknown.

Unknown.

XopW1: Yes (e.g., X. oryzae, X.prunicola, X. euvesicatoria, X. axonopodis pv. nakataecorchori)
XopW2: Yes (e.g., X. theicola)
XopW3: Yes (e.g., X. hydrangeae, X. arboricola, X. populi)
XopW4: Yes (e.g., X. hortorum, X. campestris pv. badrii)
XopW5: Yes (e.g., X. vasicola)

XopW1: No
XopW2: Remote homolog in Ralstonia ssp. (Effector candidate Rs_T3E_Hyp7)
XopW3: Remote homolog in Ralstonia ssp. (Effector candidate Rs_T3E_Hyp7)
XopW4: No
XopW5: No

Furutani A, Takaoka M, Sanada H, Noguchi Y, Oku T, Tsuno K, Ochiai H, Tsuge S (2009). Identification of novel type III secretion effectors in Xanthomonas oryzae pv. oryzae. Mol. Plant Microbe Interact. 22: 96-106. DOI: 10.1094/MPMI-22-1-0096

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.

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).