====== The Type III Effector XopAL1 from //Xanthomonas// ======

Author: [[https://www.researchgate.net/profile/Matthieu_Arlat|Matthieu Arlat]]\\
Internal reviewer: [[https://www.researchgate.net/profile/Joana_Costa12|Joana Costa]], Anna Passelergue\\
Expert reviewer: [[https://www.researchgate.net/profile/Ralf_Koebnik|Ralf Koebnik]]

Class: XopAL\\
Family: XopAL1\\
Prototype: XC_2995/XopXccE1 (//Xanthomonas campestris// pv. //campestris//; strain 8004) (Jiang //et al.//, 2009)\\
GenBank ID: [[https://www.ncbi.nlm.nih.gov/protein/AAY50043.1|AAY50043.1]] (332 aa)\\
RefSeq ID: [[https://www.ncbi.nlm.nih.gov/protein/WP_274360846.1|WP_274360846.1]] (305 aa)\\
3D structure: Unknown

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

=== How discovered? ===

XopAL1 (XC_2995) was first identified in //X. campestris// pv. //campestris// (//Xcc//) strain 8004 as a candidate type III secreted (T3S)-effector due to the presence of a plant-inducible promoter (PIP) box in its gene, XC_2995 (Jiang //et al.//, 2009).

The homolog in //Xanthomonas translucens// pv. //translucens// strain DSM 18974 (BFP94_RS19935) 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 type III secreted effector (T3E) ===

Construction of a chimeric protein between the N-terminal region of XC_2995 (XopAL1) and a truncated AvrBS1 protein (AvrBS1<sub>59-445</sub>). The chimeric gene was introduced by conjugation into Xcc8004 ∆AvrBS1 mutant or derivative of this strain mutated in //hrpF// or //hpaB// genes. The transconjugants were tested for HR elicitation on pepper ECW-10R (Jiang //et al//., 2009). These experiments suggest that the N-terminal part of XopAL1 is able to allow the translocation of the chimeric protein into pepper cells in an Hrp-dependent manner.

The homolog in //X. translucens// pv. //translucens// strain DSM 18974 (BFP94_RS19935) was shown to have a functional type III secretion signal using a reporter fusion with AvrBs1 (Zhao //et al.//, 2013; Passelergue, 2025).
=== Regulation ===

The expression of //xopAL1// gene was shown to be positively regulated by //hrpX// (Jiang //et al//., 2009) and //hrpG// (Jiang //et al//., 2009; Roux //et al//., 2015). Presence of a PIP box (Jiang //et al//., 2009; Bogdanove //et al//., 2013; Roux //et al//., 2015).

The presence of a PIP box and a properly spaced ‐10 promoter motif (TTCGB‐N15 ‐TTCGB‐N30–32 ‐YANNNT) suggests that the //xopAL1// gene of //X. translucens// pv. //translucens// strain DSM 18974 (BFP94_RS19935) is under control of HrpG and HrpX (Wengelnik & Bonas, 1996; Wengelnik et al., 1996; Koebnik et al., 2006).
=== Phenotypes ===

XopAL1<sub>//Xcc//8004</sub> is required for full virulence and growth of //X. campestris// pv. //campestris// in the host plant Chinese radish (Jiang //et al.//, 2009).
=== Localization ===

Unknown.

=== Enzymatic function ===

Unknown.

=== Interaction partners ===

Unknown.

===== Conservation =====

=== In xanthomonads ===

Yes, //X. campestris//, //X. translucens//, //X. arboricola// (Cesbron //et al//., 2015)

But also in //X. graminis// and //X. hortorum//.
=== In other plant pathogens/symbionts ===

//Acidovorax// spp., //Ralstonia solanacearum// (RipE2; Peeters //et al//., 2013), //Erwinia amylovora// (Eop3; Nissinen //et al//., 2007, HopX1<sub>Ea</sub>; Bocsanczy //et al//., 2012), //Pseudomonas// spp.
===== References =====

Bocsanczy AM, Schneider DJ, DeClerck GA, Cartinhour S, Beer SV (2012). HopX1 in //Erwinia amylovora// functions as an avirulence protein in apple and is regulated by HrpL. J. Bacteriol. 194: 553-560. DOI: [[https://doi.org/10.1128/JB.05065-11|10.1128/JB.05065-11]]

Bogdanove AJ, Koebnik R, Lu H, Furutani A, Angiuoli SV, Patil PB, Van Sluys MA, Ryan RP, Meyer DF, Han SW, Aparna G, Rajaram M, Delcher AL, Phillippy AM, Puiu D, Schatz MC, Shumway M, Sommer DD, Trapnell C, Benahmed F, Dimitrov G, Madupu R, Radune D, Sullivan S, Jha G, Ishihara H, Lee SW, Pandey A, Sharma V, Sriariyanun M, Szurek B, Vera-Cruz CM, Dorman KS, Ronald PC, Verdier V, Dow JM, Sonti RV, Tsuge S, Brendel VP, Rabinowicz PD, Leach JE, White FF, Salzberg SL (2011). Two new complete genome sequences offer insight into host and tissue specificity of plant pathogenic //Xanthomonas// spp. J. Bacteriol. 193: 5450-64. DOI: [[https://doi.org/10.1128/JB.05262-11|10.1128/JB.05262-11]]

Cesbron S, Briand M, Essakhi S, Gironde S, Boureau T, Manceau C, Saux MF, Jacques MA (2015). Comparative genomics of pathogenic and nonpathogenic strains of //Xanthomonas arboricola// unveil molecular and evolutionary events linked to pathoadaptation. Front. Plant Sci. 6:1126. DOI: [[http://doi.org/10.3389/fpls.2015.01126|10.3389/fpls.2015.01126]]

Jiang W, Jiang BL, Xu RQ, Huang JD, Wei HY, Jiang GF, Cen WJ, Liu J, Ge YY, Li GH, Su LL, Hang XH, Tang DJ, Lu GT, Feng JX, He YQ, Tang JL (2009). Identification of six type III effector genes with the PIP box in //Xanthomonas campestris// pv. //campestris// and five of them contribute individually to full pathogenicity. Mol. Plant Microbe Interact. 22: 1401-1411. DOI: [[https://doi.org/10.1094/MPMI-22-11-1401|10.1094/MPMI-22-11-1401]]

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]]

Nissinen RM, Ytterberg AJ, Bogdanove AJ, VAN Wijk KJ, Beer SV (2007). Analyses of the secretomes of //Erwinia amylovora// and selected hrp mutants reveal novel type III secreted proteins and an effect of HrpJ on extracellular harpin levels. Mol. Plant Pathol. 8: 55-67. DOI: [[https://doi.org/10.1111/j.1364-3703.2006.00370.x|10.1111/j.1364-3703.2006.00370.x]]

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.

Peeters N, Carrère S, Anisimova M, Plener L, Cazalé AC, Genin S (2013). Repertoire, unified nomenclature and evolution of the Type III effector gene set in the //Ralstonia solanacearum// species complex. BMC Genomics 14: 859. DOI: [[https://doi.org/10.1186/1471-2164-14-859|10.1186/1471-2164-14-859]]

Roux B, Bolot S, Guy E, Denancé N, Lautier M, Jardinaud MF, Fischer-Le Saux M, Portier P, Jacques MA, Gagnevin L, Pruvost O, Lauber E, Arlat M, Carrère S, Koebnik R, Noël LD (2015). Genomics and transcriptomics of //Xanthomonas campestris// species challenge the concept of core type III effectome. BMC Genomics 16: 975. DOI: [[https://doi.org/10.1186/s12864-015-2190-0|10.1186/s12864-015-2190-0]]

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).