Author: Katarina Gašić
Internal reviewer:
Expert reviewer:

Class: XopJ
Family: XopJ4
Prototype: AvrXv4 (Xanthomonas euvesicatoria pv. perforans, ex Xanthomonas campestris pv. vesicatoria; race T3strain 91-118)
RefSeq ID: WP_008572727.1 (359 aa)
Synonym: AvrXv4
3D structure: Unknown

To ascertain if X. campestris pv. vesicatoria (Xcv) translocates AvrXv4 via the hrp-encoded TTSS into plant cells during infection, the calmodulin-dependent adenylate cyclase domain (Cya) of Bordetella pertussis cyclolysin as a sensitive reporter protein was employed. It was constructed a translational C-terminal fusion of the Cya reporter to the mature AvrXv4 protein (359 amino acids [aa]) (AvrXv4-Cya) and to the first 100 aa residues of AvrXv4 (AvrXv4_1-100-Cya). Cya enzymatic activity requires eukaryotic calmodulin for the production of cAMP. Therefore, the Cya reporter protein produced in the bacterium must be translocated into the eukaryotic cell to be activated (Roden et al., 2004). Results of experiments showed that Xcv secretes AvrXv4 via the Hrp TTSS and translocates it directly through the cell wall into the interior of the plant cell. Furthermore, the N-terminal 100 aa of AvrXv4 are sufficient to target the type III-dependent secretion and translocation of the Cya reporter to plant cells (Roden et al., 2004).

Presence of a PIP box (TTCGC-N15-TTCGC) (Astua-Monge et al., 2000).

AvrXv4 is an avirulence protein in Xcv strain 91-118 that induces an XV4-dependent HR in the wild tomato relative Lycopersicon pennellii (Roden et al., 2004). AvrXv4-dependent HR also is elicited in Nicotiana benthamiana plants when they are infected with Xanthomonas strains expressing untagged AvrXv4 and HA-tagged AvrXv4-HA (Roden et al., 2004). AvrXv4 recognition by resistant plants requires a functional protease catalytic core, the domain that is conserved in all of the putative YopJ-like cysteine proteases. AvrXv4 expression in planta leads to a reduction in SUMO-modified proteins, demonstrating that AvrXv4 possesses SUMO isopeptidase activity. YopJ-like effector AvrXv4 encodes a type III SUMO protease effector that is active in the cytoplasmic compartment of plant cells (Roden et al., 2004).

AvrXv4 is localized to the plant cytoplasm (Roden et al., 2004).

Because in planta expression of AvrXv4 from X. campestris pv. vesicatoria leads to a reduction of SUMO-conjugated plant proteins, AvrXv4 presumably acts as a SUMO protease on yet unknown plant target proteins (Roden et al., 2004).

Yes (Xanthomonas perforans) (Astua-Monge et al., 2000; Roden et al., 2004; Timilsina et al., 2016).

Yes (Ralstonia solanacearum) (Lavie et al., 2002).

Astua-Monge G, Minsavage GV, Stall RE, Vallejos CE, Davis MJ, Jones JB (2000). Xv4-avrXv4: a new gene-for-gene interaction identified between Xanthomonas campestris pv. vesicatoriarace T3 and wild tomato relative Lycopersicon pennellii. Mol. Plant Microbe Interact. 13: 1346-1355. DOI: 10.1094/MPMI.2000.13.12.1346

Lavie M, Shillington E, Eguiluz C, Grimsley N, Boucher C (2002). PopP1, a new member of the YopJ/AvrRxv family of type III effector proteins, acts as a host-specificity factor and modulates aggressiveness of Ralstonia solanacearum. Mol. Plant Microbe Interact. 15: 1058-1068. DOI: 10.1094/MPMI.2002.15.10.1058

Roden J, Eardley L, Hotson A, Cao Y, Mudgett, MB (2004). Characterization of the Xanthomonas AvrXv4 effector, a SUMO protease translocated into plant cells. Mol. Plant Microbe. Interact. 17: 633-643. DOI: 10.1094/MPMI.2004.17.6.633

Timilsina S, Abrahamian P, Potnis N, Minsavage GV, White FF, Staskawicz BJ, Jones JB, Vallad GE, Goss EM (2016). Analysis of sequenced genomes of Xanthomonas perforans identifies candidate targets for resistance breeding in tomato. Phytopathology 106: 1097-1104. DOI: 10.1094/PHYTO-03-16-0119-FI