Author: Alexandre B. de Menezes
Internal reviewer: Katarina Gašić
Expert reviewer:

Class: XopJ
Family: XopJ5
Prototype: AvrXccB (Xanthomonas campestris pv. campestris; strain ATCC 33913)
RefSeq ID: NP_639077 (235 aa)
Synonym: AvrXccB
3D structure: Unknown

In Arabidopsis, AvrXccB (aka XopJ5) targets putative S- adenosyl-L-methionine-dependent methyltransferase (SAM-MT) (Liu et al., 2017).

Original discovery was through bioinformatic predictions and comparative genomics of Xanthomonas axonopodis pv. citri (Xac) and Xanthomonas campestris pv. campestris (Xcc) (da Silva et al., 2002). XopJ5 (AvrXccB) was also identified in Xcc strain 8004 as a candidate T3E due to the presence of a plant-inducible promoter (PIP) box in its gene, XC_3802 (Jiang et al., 2009).

AvrXccB, fused to a HA tag, was shown to be secreted into culture supernatants by Western blot analysis using an anti‐haemagglutinin (HA) antibody. In contrast, a T3E-defective mutant was not capable of secreting this effector (Liu et al., 2017).

The xopE1 _Xcc8004 gene (avrXccB) contains a PIP box and was shown to be controlled by hrpG and hrpX (Rongqi et al., 2006; Jiang et al., 2009).

• AvrXccB (XopJ5_Xcc8004) is not required for full virulence and growth of Xcc in the host plant Chinese radish (Jiang et al., 2009).
• XopJ5 was found to be associated with variations in disease symptoms when testing a set of 45 X. campestris pv. campestris strains on two Arabidopsis natural accessions (Guy et al., 2013).
• Experimental evidence using heterologous expression of avrXccB suggests that this protein is involved in the suppression of plant immunity. Immunity suppression in Arabidopsis involved multiple mechanisms: ectopic expression of avrXccB reduced flg22-induced callose deposition and ROS production, while avrXccB expression in Arabidopsis protoplasts inhibited the promoter activity of resistance gene NHO1. Heterologous expression of avrXccB led to an increase in the in-planta population of Xcc B186 and Pst DC300 in Arabidopsis. Conversely, avrXccB mutants were compromised in their ability to inhibit MAMP-induced immunity (callose deposition, ROS production and defence-related genes in Arabidopsis protoplasts) (Liu et al., 2017).

Plant plasma membrane, confirmed experimentally through GFP-tagged AvrXccB expression in transgenic Arabidopsis. The putative N ‐myristoylation motif is essential for its localization (Thieme et al., 2007; Liu et al., 2017).

Cysteine protease/acetyltransferase (putative) (Liu et al., 2017). Point mutations in the catalytic triad (conserved with other YopJ-like proteins which also function as protease/acetyltransferases) compromised NOH1 promoter activity and were deprived of their abilities to suppress flg22-induced callose deposition and ROS production (Liu et al., 2017).

AvrXccB interacts with S ‐adenosyl‐L‐methionine‐dependent methyltransferases SAM‐MT1 and SAM‐MT2 in Arabidopsis. Interaction with SAM-MT1 in Arabidopsis occurs through SAM-MT1's C-terminal domain. AvrXccB-SAM-MT1 interaction was determined experimentally using in-vitro pull-down assays and Co-IP assays (Liu et al., 2017).

Yes. YopJ-like effectors such as AvrBsT in Xcv or Xcc, XopJ in Xcv.

Yes. YopJ-like effectors HopZ1a in P. syringae and Pop2 in R. solanacearum.

da Silva AC, Ferro JA, Reinach FC, Farah CS, Furlan LR, Quaggio RB, Monteiro-Vitorello CB, Van Sluys MA, Almeida NF, Alves LM, do Amaral AM, Bertolini MC, Camargo LE, Camarotte G, Cannavan F, Cardozo J, Chambergo F, Ciapina LP, Cicarelli RM, Coutinho LL, Cursino-Santos JR, El-Dorry H, Faria JB, Ferreira AJ, Ferreira RC, Ferro MI, Formighieri EF, Franco MC, Greggio CC, Gruber A, Katsuyama AM, Kishi LT, Leite RP, Lemos EG, Lemos MV, Locali EC, Machado MA, Madeira AM, Martinez-Rossi NM, Martins EC, Meidanis J, Menck CF, Miyaki CY, Moon DH, Moreira LM, Novo MT, Okura VK, Oliveira MC, Oliveira VR, Pereira HA, Rossi A, Sena JA, Silva C, de Souza RF, Spinola LA, Takita MA, Tamura RE, Teixeira EC, Tezza RI, Trindade dos Santos M, Truffi D, Tsai SM, White FF, Setubal JC, Kitajima JP (2002). Comparison of the genomes of two Xanthomonas pathogens with differing host specificities. Nature 417: 459-463. DOI: 10.1038/417459a

Guy E, Genissel A, Hajri A, Chabannes M, David P, Carrere S, Lautier M, Roux B, Boureau T, Arlat M, Poussier S, Noël LD (2013). Natural genetic variation of Xanthomonas campestris pv. campestris pathogenicity on Arabidopsis revealed by association and reverse genetics. mBio 4: e00538-12. DOI: 10.1128/mBio.00538-12. Erratum in: MBio (2013) 4: e00978-13.

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: 10.1094/mpmi-22-11-1401

Liu L, Wang Y, Cui F, Fang A, Wang S, Wang J, Wei C, Li S, Sun W (2017). The type III effector AvrXccB in Xanthomonas campestris pv. campestris targets putative methyltransferases and suppresses innate immunity in Arabidopsis. Mol. Plant Pathol. 18: 768-782. DOI: 10.1111/mpp.12435

Rongqi X, Xianzhen L, Hongyu W, Bole J, Kai L, Yongqiang H, Jiaxuan F, Jiliang T (2006). Regulation of eight avr by hrpG and hrpX in Xanthomonas campestris pv. campestris and their role in pathogenicity. Prog. Nat. Sci. 16: 1288-1294. DOI: 10.1080/10020070612330143

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