====== The Type III Effector XopJ6 from //Xanthomonas// ======

Author: [[https://www.researchgate.net/profile/Laurent-Noel-3|Laurent Noël]]\\
Reviewer: [[https://www.researchgate.net/profile/Ralf_Koebnik|Ralf Koebnik]]

Class: XopJ\\
Family: XopJ6\\
Prototype: XopJ6 (//Xanthomonas campestris //pv. //campestris//; strain CN06)\\
RefSeq ID: [[https://www.ncbi.nlm.nih.gov/protein/WP_196765268.1|WP_196765268.1]] (471 aa)\\
3D structure: Unknown

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

=== How discovered? ===

XopJ6 was initially identified in //Xanthomonas campestris //pv. //campestris //as a homolog of //Ralstonia pseudosolanacearum //, the presence of which correlated with induction of an hypersensitive response (HR) on //Brassacia oleracea// cv. clovis F1 (Lauber //et al//., 2024).
=== (Experimental) evidence for being a T3E ===

  * XopJ6 is a homolog of PopP2, with 35% overall sequence identity with a good conservation of the acetyltransferase domain (Lauber //et al//., 2024).
  * //xopJ6//  induces HR on cauliflower in a type III secretion-dependent-manner (Lauber //et al//., 2024).
  * In Arabidopsis, XopJ6 effector-triggered immunity (ETI) is mediated by two nuclear proteins RRS1 and RPS4 (Lauber //et al//., 2024).
  * No direct experimental demonstration for translocation.

=== Genomic organization ===

//xopJ6//  is present on a ca. 9-kb transposable element named Tn//6714//. It was found in multiple identical copies, likely due to recent transposition events (Lauber //et al//., 2024). Many //Xanthomonas campestris //pv. //campestris //strains do not contain any// xopJ6 //gene and are still potent and adapted pathogenic strains (Lauber //et al//., 2024).

=== Regulation ===

//xopJ6//  promoters possess a PIP-box motif (Lauber //et al//., 2024). Expression of //xopJ6//  is induced in the //hrp//-inducing medium MME or by the //hrpG//* gain-of-function allele of //hrpG//  in a //hrpG//- and //hrpX//-dependent manner (Lauber //et al//., 2024). Copy number variation of //xopJ6//  results in variable levels of transcription.

=== Phenotypes ===

  * //xopJ6//  induces an hypersensitive response and ETI on the cauliflower (Brassica oleracea) cv. Clovis F1 (Lauber //et al//., 2024).
  * //xopJ6//  induces ETI in //Arabidopsis thaliana//  in an RRS1-R- and RPS4-dependent manner (Lauber //et al//., 2024).
  * //xopJ6 //delivered by //Pseudomonas fluorescens//  Pfo-1 induces HR in //Arabidopsis thaliana//  in an RRS1-R-, EDS1- and RPS4-dependent manner (Lauber //et al//., 2024).
  * //xopJ6//  is able to dampen flg22-induced PTI responses in //Nicotiana benthamiana //  (Lauber //et al//., 2024)//.//
  * //xopJ6//  quantitatively contributes to //Xanthomonas campestris//  pv. //campestris//  pathogenicity in susceptible accessions Col-0 and Sf-2 of Arabidopsis: //xopJ6//  mutants are less virulent while those overexpressing //xopJ6//  are more virulent (Lauber //et al//., 2024).
=== Localization ===

XopJ6-CFP has a nucleo-cytoplasmic localization upon //Agrobacterium//-mediated expression in //N. benthamiana//  (Lauber //et al//., 2024).

=== Enzymatic function ===

Recombinant XopJ6 purified from //E. coli //encodes an acetyl transferase able to acetylate Arabidopsis WRKY22 (Lauber //et al//., 2024).

=== Interaction partners ===

  * XopJ6 interacts with RRS1-R WRKY domain in yeast two-hybrid experiments (Lauber //et al//., 2024).
  * XopJ6 interacts with Arabidopdis RRS1-R resistance protein and WRKY22 transcription factor (Lauber //et al//., 2024).
  * A single AA substituion (N382K) abolishes interaction with Arabidopsis WRKY22 and RRS1-R and is required for ETI in Arabidopsis and cauliflower (Lauber //et al//., 2024).
  * WT XopJ6 and XopJ6<sup>N382K</sup>   both suppress Flg22 ROS burst in a WRKY-independent manner (Lauber //et al//., 2024).

===== Conservation =====

=== In xanthomonads ===

By 2024, xopJ6 has only been detected in //Xanthomonas campestris// pv. //campestris// (Lauber //et al//., 2024) and in //Xanthomonas translucens// pv. //graminis//.
=== In other plant pathogens/symbionts ===

XopJ6 is a homolog of the type III effector PopP2 from //Rastonia pseudosolanacearum//. Homologs are also present in strains of //Collimonas// and //Duganella//.

===== References =====

Lauber E, González-Fuente M, Escouboué M, Vicédo C, Luneau JS, Pouzet C, Jauneau A, Gris C, Zhang ZM, Pichereaux C, Carrère S, Deslandes L, Noël LD (2024). Bacterial host adaptation through sequence and structural variations of a single type III effector gene. iScience 27: 109224. DOI: [[https://doi.org/10.1016/j.isci.2024.109224|10.1016/j.isci.2024.109224]]