Author: Anna Passelergue
Internal reviewer: Ralf Koebnik

Class: XopJ
Family: XopJ8
Prototype: FZ025_RS03100 (Xanthomonas hyacinthi, strain CFBP 1156)
GenBank ID: QGY75705.1 (362 aa)
RefSeq ID: WP_104559054.1 (362 aa).
3D structure: Unknown

XopJ8 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). Additional evidence came from the presence of conserved myristoylation and palmitoylation signals at the N terminus (Nimchuk et al., 2000; Thieme et al., 2007). The protein was also predicted as a type III effector by Effectidor II, a pan-genomic AI-based algorithm for the prediction of type III secretion system effectors (Wagner et al., 2025). The prototype gene in X. hyacinthi strain CFBP 1156 is flanked by two IS3-family insertion sequences.

XopJ8 was shown to have a functional type III secretion signal using a reporter fusion with AvrBs1 (Zhao et al., 2013).

The presence of a PIP box and a properly spaced ‐10 promoter motif (TTCGB‐N₁₅ ‐TTCGB‐N_30–32 ‐YANNNT) suggests that the xopJ8 gene is under control of HrpG and HrpX (Wengelnik & Bonas, 1996; Wengelnik et al., 1996; Koebnik et al., 2006).

Unknown.

The presence of conserved myristoylation and palmitoylation signals at the N terminus suggests that the protein is localized to the plasma membrane in the plant host cell (Nimchuk et al., 2000; Thieme et al., 2007).

Unknown.

Unknown.

Yes (e.g., X. citri, frameshifted versions of the gene exist in X. graminis pv. graminis).

Yes (e.g., Pseudomonas syringae, Ralstonia ssp.].

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

Nimchuk Z, Marois E, Kjemtrup S, Leister RT, Katagiri F, Dangl JL (2000). Eukaryotic fatty acylation drives plasma membrane targeting and enhances function of several type III effector proteins from Pseudomonas syringae. Cell 101: 353-363. DOI: 10.1016/s0092-8674(00)80846-6

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.

Thieme F, Szczesny R, Urban A, Kirchner O, Hause G, Bonas U (2007). New type III effectors from Xanthomonas campestris pv. vesicatoria trigger plant reactions dependent on a conserved N-myristoylation motif. Mol. Plant Microbe Interact. 20: 1250-1261. DOI: 10.1094/MPMI-20-10-1250

Wagner N, Baumer E, Lyubman I, Shimony Y, Bracha N, Martins L, Potnis N, Chang JH, Teper D, Koebnik R, Pupko T (2025). Effectidor II: a pan-genomic AI-based algorithm for the prediction of type III secretion system effectors. Bioinformatics 41: btaf272. DOI: 10.1093/bioinformatics/btaf272

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).