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

Author: [[https://www.researchgate.net/profile/Ralf-Koebnik|Ralf Koebnik]]\\
Expert reviewer: **WANTED!**

Class: XopBB\\
Family: XopBB\\
Prototype: ELAGFFLI_02299 (//Xanthomonas ////hortorum// pv. //pelargonii//; strain 305)

GenBank ID: [[https://www.ncbi.nlm.nih.gov/protein/CAD0333498.1|CAD0333498]] (332 aa)\\
RefSeq ID: [[https://www.ncbi.nlm.nih.gov/protein/WP_251761698.1|WP_251761698.1]] (220 aa, corresponding to the C-terminal domain)\\
3D structure:

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

=== How discovered? ===

XopBB was discovered using a machine-learning approach for the prediction of T3Es (Wagner //et al.//, 2022, 2023).
=== (Experimental) evidence for being a T3E ===

To examine the translocation of the predicted T3E, a reporter system based on the delivery of a truncated form of the //Xanthomonas euvesicatoria //T3E AvrBs2 (amino acids 62–574) into susceptible plant cells was utilized. AvrBs2<sub>62–574</sub> lacks the type 3 translocation signal, but is sufficient to elicit a hypersensitive response (HR) in plants expressing the //Bs2// resistance gene. A fusion of the XopBB ORF, including 24 bp upstream of its ATG start codon, with AvrBs2<sub>62–574</sub> elicited HR response in the pepper line ECW20R, which encodes a functional //Bs2// resistance gene (Wagner //et al.//, 2023).
=== Regulation ===

The //xopBB// gene contains a perfect PIP box in its promoter region and is likely co-regulated with the T3SS under control of HrpG and HrpX (Wagner //et al.//, 2023).
=== Phenotypes ===

Unknown.

=== Localization ===

Unknown.

=== Enzymatic function ===

Unknown.

=== Interaction partners ===

Unknown.

===== Conservation =====

=== In xanthomonads ===

Yes, //X. arboricola// and //X. hydrangeae// (Wagner //et al.//, 2023).
=== In other plant pathogens/symbionts ===

Yes, in species of //Acidovorax // (e.g. //A. avenae//, //A. citrulli//, //A. oryzae//) (Wagner //et al.//, 2023). XopBB is distantly related to HopF2 (syn. AvrPphF) from the //Pseudomonas syringae// species complex, e.g. //P. amygdali//, //P. cannabina// (ca. 30 % amino acid sequence identity).

===== References =====

Wagner N, Avram O, Gold-Binshtok D, Zerah B, Teper D, Pupko T (2022). Effectidor: an automated machine-learning-based web server for the prediction of type-III secretion system effectors. Bioinformatics 38: 2341-2343. DOI: [[https://doi.org/10.1093/bioinformatics/btac087|10.1093/bioinformatics/btac087]]

Wagner N, Ben-Meir D, Teper D, Pupko T (2023). Complete genome sequence of an Israeli isolate of //Xanthomonas hortorum// pv. //pelargonii// strain 305 and novel type III effectors identified in //Xanthomonas//. Front. Plant Sci. 14: 1155341. DOI: [[https://doi.org/10.3389/fpls.2023.1155341|10.3389/fpls.2023.1155341]]