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Molecular Diagnosis and Diversity for Regulated Xanthomonas
Bacterial virulence factors
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Class: XopB
Family: XopB
Prototype: XopB (Xanthomonas euvesicatoria pv. euvesicatoria aka Xanthomonas campestris pv. vescicatoria; strain 85-10)
RefSeq ID: WP_039417318.1
3D structure: unknown
Biological function
How discovered? XopB was discovered in a cDNA-AFLP screen.[1]
(Experimental) evidence for being a T3E: A chimeric protein consisting of a C-terminally truncated XopB where the last 52 residues (5 kDa) were replaced by the triple c-myc epitope (5 kDa) was secreted into culture supernatants of a strain with a constitutively active form of hrpG in a type III secretion-dependent manner.[1] XopB belongs to translocation class B.[3]
Regulation: The xopB gene was shown to be expressed in a hrpG- and hrpX-dependent manner.[1] Presence of a PIP and ‐10 box (TTCGB‐N15 ‐TTCGB‐N30–32 ‐YANNNT).[3]
Phenotypes: A deletion of xopB did not affect pathogenicity or bacterial growth in plants.[1] Later it was found that XopB contributes to disease symptoms and bacterial growth.[3] When expressed in yeast, XopB attenuated cell proliferation.[2] XopB caused a fast and confluent cell death when transiently expressed in the nonhost Nicotiana benthamiana leaves, whereas its expression in host tomato leaves did not result in a visible phenotype, even 7 days after agroinfiltration.[2] XopB suppresses pathogen‐associated molecular pattern (PAMP)‐triggered plant defense gene expression and inhibits cell death reactions induced by different T3Es, thus suppressing defense responses related to both PAMP‐triggered immunity (PTI) and effector‐triggered immunity (ETI).[3] Interestingly, a XopB point mutant derivative was defective in the suppression of ETI‐related responses, but still interfered with vesicle trafficking and was only slightly affected with regard to the suppression of defense gene induction, suggesting that XopB‐mediated suppression of PTI and ETI is dependent on different mechanisms that can be functionally separated.[3] A deletion of xopB caused a prominent increase in cell wall-bound invertase activity, which might be linked to defense responses because an increase in the apoplastic hexose-to-sucrose ratio has been suggested to strengthen plant defense.[4]
Localisation: XopB localizes to the Golgi apparatus and cytoplasm of the plant cell and interferes with eukaryotic vesicle trafficking.[3]
Enzymatic function:
Interaction partners:
Conservation
In xanthomonads: Yes (e.g. X. fragariae, X. gardneri, X. oryzae, X. vasicola)[5]
In other plant pathogens/symbionts: Yes (e.g. Pseudomonas spp., Ralstonia solanacearum, Acidovorax spp., Pantoea agglomerans)[3]
References
