Author: Steven J. Roberts
Internal reviewer: Christian Vernière
Expert reviewer:

Class: XopAH
Family: XopAH
Prototype: XopAH (AvrXccC) (Xanthomonas campestris pv. campestris strain 8004 - Qian et al., 2005)
RefSeq ID: ABQ10636.1 (440 aa) (gene EF529437.1 1323 bp)
3D structure: Unknown

AvrXccC was described during a genome comparison analysis between Xanthomonas citri pv. citri and X. campestris pv. campestris Xcc strain ATCC 33913 = NCPPB 528 (Da Silva et al., 2002) and in a search of annotated genome (Castenada et al., 2005).

Secreted XopAH (AvrXccC) proteins were detected in culture fluid from Xcc 8004 and hrcV mutant complemented strains but not from the hrcV mutant (Wang et al., 2007). Insertion and deletion mutants affecting the locus (Xcc2109) in the type strain (Xcc 528) resulted in loss of virulence on the host Florida Broad Leaf Mustard (Castenada et al., 2005).

Promoter activity assays showed that the expression of XopAH (avrXccC) is hrpG/hrpX-dependent (Wang et al., 2007).

This effector is required for full virulence in the susceptible host cabbage (Brassica oleracea) (Wang et al., 2007) and results in avirulence in the resistant host mustard (Brassica napiformis) (Castenada et al., 2005; He et al., 2007; Wang et al., 2007). The intact AvrB-AvrC domain of AvrXccC₈₀₀₄ is essential and sufficient to elicit defense responses in an Arabidopsis resistant ecotype (Col-0) (Ho et al., 2013).

In the interaction Arabidopsis / Xcc strain 8004, AvrXccC₈₀₀₄ not only presented its avirulence activity to trigger plant defense response but also possessed its virulence activity to manipulate the component involved in the ABA signalling pathway leading to an increase of ABA concentrations (Ho et al., 2013).

XopAH (AvrXccC) is anchored to the plant plasma membrane, and the N‐terminal myristoylation site (amino acids 2–7: GLcaSK) is essential for its localization (Wang et al., 2007).

XopAH has a Fido/AvrB domain derived from the fic (cyclic adenosine monophosphate (cAMP)-induced filamentation and doc (death on curing) domains (Kinch et al., 2009). Structural comparisons resulted in the inclusion of similar segments of the T3 effector AvrB from Pseudomonas syringae species (Kinch et al., 2009; White et al., 2009). T3 effectors in the XopAH group could trans-AMPylate plant host proteins. AMPylation represents a posttranslational modification used to stably modify proteins with AMP (Kinch et al., 2009).

Not known ?

In Xanthomonas campestris pv. campestris. XopAH is also present in X. arboricola pv. juglandis within strains causing Walnut Blight but is absent from the strains causing vertical oozing canker (Cesbron et al., 2015).

Yes (AvrB Pseudomonas savastanoi, Pseudomonas syringae)

Castenada A, Reddy JD, El-Yacoubi B, Gabriel DW (2005). Mutagenesis of all eight avr genes in Xanthomonas campestris pv. campestris had no detected effect on pathogenicity, but one avr gene affected race specificity. Mol. Plant-Microbe Interact. 18: 1306-1317. DOI: 10.1094/MPMI-18-1306.

Cesbron, S., Briand, M., Essakhi, S., Gironde, S., Boureau, T., Manceau, C., Fischer-Le Saux, M., and Jacques, M. A. 2015.</font><font 10.5pt/inherit;;inherit;;inherit>Comparative genomics of pathogenic and nonpathogenic strains of CKGE_TMP_i Xanthomonas arboricola CKGE_TMP_i unveil molecular and evolutionary events linked to pathoadaptation. Frontiers in Plant Science 6:1126.

Da Silva, A. C., Ferro, J. A., Reinach, F. C., Farah, C. S., Furlan, L. R., Quaggio, R. B., Monteiro-Vitorello, C. B., Van Sluys, M. A., Almeida, N. F., Alves, L. M., Do Amaral, A. M., Bertolini, M. C., Camargo, L. E., Camarotte, G., Cannavan, F., Cardozo, J., Chambergo, F., Ciapina, L. P., Cicarelli, R. M., Coutinho, L. L., Cursino-Santos, J. R., El-Dorry, H., Faria, J. B., Ferreira, A. J., Ferreira, R. C., Ferro, M. I., Formighieri, E. F., Franco, M. C., Greggio, C. C., Gruber, A., Katsuyama, A. M., Kishi, L. T., Leite, R. P., Lemos, E. G., Lemos, M. V., Locali, E. C., Machado, M. A., Madeira, A. M., Martinez-Rossi, N. M., Martins, E. C., Meidanis, J., Menck, C. F., Miyaki, C. Y., Moon, D. H., Moreira, L. M., Novo, M. T., Okura, V. K., Oliveira, M. C., Oliveira, V. R., Pereira, H. A., Rossi, A., Sena, J. A., Silva, C., De Souza, R. F., Spinola, L. A., Takita, M. A., Tamura, R. E., Teixeira, E. C., Tezza, R. I., Trindade dos Santos, M., Truffi, D., Tsai, S. M., White, F. F., Setubal, J. C., and Kitajima, J. P. 2002. Comparison of the genomes of two Xanthomonas pathogens with differing host specificities. Nature 417: 459-463. DOI: 10.1038/417459a

He, Y. Q., Zhang, L., Jiang, B. L., Zhang, Z. C., Xu, R. Q., Tang, D. J., Qin, J., Jiang, W., Zhang, X., Liao, J., Cao, J. R., Zhang, S. S., Wei, M. L., Liang, X. X., Lu, G. T., Feng, J. X., Chen, B., Cheng, J., and Tang, J. L. 2007. Comparative and functional genomics reveals genetic diversity and determinants of host specificity among reference strains and a large collection of Chinese isolates of the phytopathogen Xanthomonas campestris pv. campestris. Genome Biology 8: R218. DOI: 10.1186/gb-2007-8-10-r218

Ho, Y. P., Tan, C. M., Li, M. Y., Lin, H., Deng, W. L., and Yang, J. Y. 2013. The AvrB_AvrC Domain of AvrXccC of Xanthomonas campestris pv. campestris Is Required to Elicit Plant Defense Responses and Manipulate ABA Homeostasis. Mol. Plant-Microbe Interact. 26: 419-430. DOI: 10.1094/mpmi-06-12-0164-r

Kinch, L. N., Yarbrough, M. L., Orth, K., and Grishin, N. V. 2009. Fido, a Novel AMPylation Domain Common to Fic, Doc, and AvrB. Plos One 4: e5818. DOI: 10.1371/journal.pone.0005818

Qian W, Jia Y, Ren SX, He Y Q, Feng JX, Lu LF, Sun Q, Ying G, Tang DJ, Tang H, Wu W, Hao P, Wang L, Jiang BL, Zeng S, Gu WY, Lu G, Rong L, Tian Y, Yao Z, Fu G, Chen B, Fang R, Qiang B, Chen Z, Zhao GP, Tang JL and He C (2005). Comparative and functional genomic analyses of the pathogenicity of phytopathogen Xanthomonas campestris pv. campestris. Genome Research 15: 757-767. DOI: 10.1101/gr.3378705.

Wang L, Tang X, He C (2007). The bifunctional effector AvrXccC of Xanthomonas campestris pv. campestris requires plasma membrane-anchoring for host recognition. Mol. Plant Pathol. 8: 491-501. DOI: 10.1111/j.1364-3703.2007.00409.x.

White, F. F., Potnis, N., Jones, J. B., and Koebnik, R. 2009. The type III effectors of Xanthomonas. Mol. Plant Pathol. 10: 749-766. DOI: 10.1111/j.1364-3703.2009.00590.x