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Molecular Diagnosis and Diversity for Regulated Xanthomonas
Bacterial virulence factors
This DokuWiki is based upon work from COST Action CA16107 EuroXanth, supported by COST (European Cooperation in Science and Technology)
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Authors: Ralf Koebnik & Trainees from the 2nd EuroXanth Training School (Daiva Burokienė, Edyta Đermić, Dagmar Stehlikova, Mariya Stoyanova)
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Class: XopAJ
Family: XopAJ
Prototype: XopAJ (Xanthomonas oryzae pv. oryzicola; strain BLS256)
RefSeq ID: WP_014504815.1 (421 aa)
Synonym: AvrRxo1
3D structure: 4Z8Q, 4Z8T, 4Z8U, 4Z8U (Han et al., 2015)
Maize lines that contain the single dominant gene Rxo1 exhibit a rapid hypersensitive response (HR) after infiltration with the rice bacterial streak pathogen Xanthomonas oryzae pv. oryzicola, but not with the rice bacterial blight pathogen X. oryzae pv. oryzae. The avirulence effector gene that corresponds to Rxo1, designated avrRxo1, was identified in an X. oryzae pv. oryzicola genomic library (Zhao et al., 2004).
When expressed in an X. oryzae pv. oryzae hrpC mutant that is deficient in the type III secretion system, avrRxo1 did not elicit the HR, indicating that the avrRxo1-Rxo1 interaction is dependent on type III secretion (Zhao et al., 2004). Transient expression in maize lines carrying Rxo1 resulted in cell death, suggesting that AvrRxo1 functions from inside maize cells to elicit Rxo1-dependent pathogen recognition (Zhao et al., 2004).
When introduced into X. oryzae pv. oryzae, clones containing avrRxo1 induced an HR on maize with Rxo1, but not on maize without Rxo1 (Zhao et al., 2004).
Rxo1 has a nucleotide-binding site-leucine-rich repeat structure, similar to many previously identified R genes (Zhao et al., 2005). Rxo1 functions after transfer as a transgene to rice, demonstrating the feasibility of nonhost R gene transfer between cereals (Zhao et al., 2005; Xie et al., 2007).
AvrRxo1 was found to be cytotoxic when expressed in yeast and caused chlorosis and patches of cell death in the infiltrated leaf areas upon transient expression in tomato and Nicotiana benthamiana (Salomon et al., 2011).
Expression of AvrRxo1-ORF1 suppresses bacterial growth in a manner dependent on the T4 polynucleotide kinase motif.
The gene prduct of the adjecent gene, avrRxo1-ORF2, functions to suppress the bacteriostatic activity of AvrRxo1-ORF1 in bacterial cells.
Transient expression of avrRxo1 in onion cells after biolistic delivery revealed that the protein product was associated with the plasma membrane (Zhao et al., 2004).
AvrRxo1-ORF1 has a T4 polynucleotide kinase domain.
Molecular modeling was used to decipher structural mechanisms of AvrRxo1-Rxo1 interaction (Bahadur & Basak, 2014).
Although AvrRxo1-ORF2 binds AvrRxo1-ORF1, it is structurally different from typical effector-binding chaperones, in that it has a distinct fold containing a novel kinase-binding domain. AvrRxo1-ORF2 functions to suppress the bacteriostatic activity of AvrRxo1-ORF1 in bacterial cells.
Yes (e.g. X. alfalfae, X. axonopodis, X. bromi, X. euvesicatoria, X. oryzae, X. translucens)
Yes (Acidovorax spp.)
