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--- bacteria:t3e:xopaj [2020/08/14 00:52]
jfpothier [Conservation]
+++ bacteria:t3e:xopaj [2022/06/22 14:01] (current)
rkoebnik [Biological function]
@@ Line 3: / Line 3: @@
 Authors: [[https://www.researchgate.net/profile/Ralf_Koebnik|Ralf Koebnik]] & Trainees from the 2<sup>nd</sup>  EuroXanth Training School ([[https://www.researchgate.net/profile/Daiva_Burokiene|Daiva Burokienė]], [[https://www.researchgate.net/profile/ermic_Edyta|Edyta Đermić]], [[https://www.researchgate.net/profile/Dagmar_Stehlikova|Dagmar Stehlikova]], [[https://www.researchgate.net/profile/Mariya_Stoyanova|Mariya Stoyanova]])\\
 Internal reviewer: [[https://www.researchgate.net/profile/Joel_Pothier2|Joël F. Pothier]]\\
-Expert reviewer: FIXME
+Expert reviewer: [[https://www.researchgate.net/profile/Lindsay_Triplett|Lindsay Triplett]]
+Class: XopAJ\\
+Family: XopAJ\\
+Prototype: XopAJ (//Xanthomonas oryzae// pv. //oryzicola//; strain BLS256)\\
+RefSeq ID: [[https://www.ncbi.nlm.nih.gov/protein/WP_014504815.1|WP_014504815.1 ]] (obsolete version suggested to be replaced by [[https://www.ncbi.nlm.nih.gov/protein/WP_153816726.1|WP_153816726.1]]) (421 aa)\\
+Synonym: AvrRxo1\\
+D structure: [[https://www.rcsb.org/structure/4Z8Q|4Z8Q]], [[https://www.rcsb.org/structure/4Z8T|4Z8T]], [[https://www.rcsb.org/structure/4Z8U|4Z8U]], [[https://www.rcsb.org/structure/4Z8V|4Z8V]] (Han //et al.//, 2015)
+====== XopAJ ======
+Authors: [[https://www.researchgate.net/profile/Ralf_Koebnik|Ralf Koebnik]] & Trainees from the 2<sup>nd</sup>  EuroXanth Training School ([[https://www.researchgate.net/profile/Daiva_Burokiene|Daiva Burokienė]], [[https://www.researchgate.net/profile/ermic_Edyta|Edyta Đermić]], [[https://www.researchgate.net/profile/Dagmar_Stehlikova|Dagmar Stehlikova]], [[https://www.researchgate.net/profile/Mariya_Stoyanova|Mariya Stoyanova]])\\
+Internal reviewer: [[https://www.researchgate.net/profile/Joel_Pothier2|Joël F. Pothier]]\\
+Expert reviewer: [[https://www.researchgate.net/profile/Lindsay_Triplett|Lindsay Triplett]]
 Class: XopAJ\\
@@ Line 15: / Line 27: @@
 === How discovered? ===
-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// (//Xoc//), but not with the rice bacterial blight pathogen //X. oryzae// pv. //oryzae// (//Xoo//) (Zhao //et al.//, 2004). The avirulence effector gene that corresponds to //Rxo1//, designated //avrRxo1//, was identified in an //Xoc// genomic library (Zhao //et al.//, 2004).
+Maize lines that contain the single dominant gene //Rxo1// exhibit a rapid hypersensitive response (HR) after infiltration with the nonhost rice bacterial streak pathogen //Xanthomonas oryzae// pv. //oryzicola// (//Xoc//) and some strains of the maize pathogen //Paraburkholderia andropogonis//, but not with the rice bacterial blight pathogen //X. oryzae// pv. //oryzae// (//Xoo//) (Zhao //et al.//, 2004). The avirulence effector gene that corresponds to //Rxo1//, designated //avrRxo1//, was identified in an //Xoc// genomic library (Zhao //et al.//, 2004).
 === (Experimental) evidence for being a T3E ===
@@ Line 27: / Line 39: @@
   * When introduced into //Xoo//, 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).
+  * AvrRxo1 is 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).
   * Variants of AvrRxo1 were found to suppress the HR caused by the non-host resistance recognition of //Xoo//  by //N. benthamiana//  (Liu //et al.//, 2014).
-  * Among four //avrRxo1//  alleles from different //Xoc//  strains, it was concluded that the toxicity is abolished by a single amino acid substitution at residue 344 in two AvrRxo1 variants (Liu //et al.//, 2014).
+  * Among four //avrRxo1//  alleles from different //Xoc//  strains, toxicity is abolished by a single amino acid substitution at residue 344 in two AvrRxo1 variants (Liu //et al.//, 2014).
   * The ATP/GTP binding site motif A and the NLS are required for both the avirulence activity and the suppression of non-host resistance (Liu //et al.//, 2014).
-  * AvrRxo1 has a T4 polynucleotide kinase domain, and expression of AvrRxo1 suppresses bacterial growth in a manner dependent on the kinase motif (Han //et al.//, 2015).
+  * AvrRxo1 has a T4 polynucleotide kinase domain and a structure homologous to that of Zeta toxins, and expression of AvrRxo1 suppresses bacterial growth in a manner dependent on the kinase motif (Han //et al.//, 2015).
-  * The gene product of the adjacent gene, AvrRxo1-ORF2 aka Arc1, functions to suppress the bacteriostatic activity of AvrRxo1 in bacterial cells (Han //et al.//, 2015).
+  * The gene product of the adjacent gene, AvrRxo1-ORF2 aka Arc1, suppresses the bacteriostatic activity of AvrRxo1 in bacterial cells (Han //et al.//, 2015).
-  * AvrRxo1 and its binding partner Arc1 function as a toxin-antitoxin system when expressed in //Escherichia coli//  (Triplett //et al.//, 2016).
+  * AvrRxo1 and its binding partner Arc1 function as a toxin-antitoxin system when expressed in //Escherichia coli//  (Triplett //et al.//, 2016). Bacterial toxicity is dependent on bacterial growth rate and conferred by diverse AvrRxo1 homologs from //X. euvesicatoria//, //B. andropogonis//, and //X. translucens//.
   * XopAJ<sub>Xcv85-10</sub>  inhibited activation of a PTI-inducible promoter by the bacterial peptide elf18 in Arabidopsis protoplasts and by flg22 in tomato protoplasts. This effector inhibited flg22-induced callose deposition //in planta//  and enhanced disease symptoms caused by attenuated// Pseudomonas syringae//  bacteria (Popov //et al.//, 2016).
-  * Mutation of the catalytic aspartic acid residue D<sub>193</sub>  abolished AvrRxo1 kinase activity and several phenotypes of AvrRxo1, including toxicity in yeast, bacteria, and plants, suppression of the flg22-triggered ROS burst, and ability to trigger an //R//  gene-mediated hypersensitive response. A mutation in the Walker A ATP-binding motif abolished the toxicity of AvrRxo1, but did not abolish the 3'-NADP production, virulence enhancement, ROS suppression, or HR-triggering phenotypes of AvrRxo1. These results demonstrated that AvrRxo1 targets the central metabolite and redox carrier NAD //in planta//, and that this catalytic activity is required for toxicity and suppression of the ROS burst (Shidore //et al.//, 2017).
+  * AvrRxo1 is a kinase that converts NAD to 3'-NADP and NAADP to 3'-NAADP. Mutation of the catalytic aspartic acid residue D<sub>193</sub>  abolished AvrRxo1 kinase activity and several phenotypes of AvrRxo1, including toxicity in yeast, bacteria, and plants, suppression of the flg22-triggered ROS burst, and ability to trigger an //R//  gene-mediated hypersensitive response in rice. A mutation in the Walker A ATP-binding motif, which reduced 3'-NADP production by roughly 90%, abolished the toxicity of AvrRxo1 in bacteria, yeast, and plants. However, this mutation did not abolish the virulence enhancement, ROS suppression, or HR-triggering phenotypes of AvrRxo1. These results demonstrate that AvrRxo1 kinase activity is required for all the known phenotypes of AvrRxo1, but that toxicity is dose-dependent (Shidore //et al.//, 2017).
   * AvrRxo1 targets the cysteine protease RD21A, which is required for drought-induced immunity (Liu //et al.//, 2020).
+  * AvrRxo1 enhances //Xoc//  virulence and inhibits stomatal immunity by targeting and degrading rice OsPDX1 (pyridoxal phosphate synthase), thereby reducing vitamin B6 (VB6) levels in rice (Liu //et al.//, 2022).
 === Localization ===
-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).
+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). However, later studies using fluorescently-tagged AvrRxo1 indicate localization in the nucleus and cytoplasm as well (Liu //et al//., 2014, Triplett// et al.//, 2016, Liu //et al.//, 2020).
 === Enzymatic function ===
-AvrRxo1 has a T4 polynucleotide kinase domain (Han //et al.//, 2015; Wu //et al//., 2015).
+AvrRxo1 has a T4 polynucleotide kinase domain (Han //et al.//, 2015; Wu //et al//., 2015). AvrRxo1 is an ATP-dependent protease (Liu //et al.//, 2022).
-AvrRxo1 is an authentic phosphotransferase that produces two novel metabolites by phosphorylating nicotinamide/nicotinic acid adenine dinucleotide at the adenosine 3'-hydroxyl group. Both products of AvrRxo1, 3'-NADP and 3'-nicotinic acid adenine dinucleotide phosphate (3'-NAADP), had been used before as inhibitors or signaling molecules but were regarded as "artificial" compounds until then (Schuebel //et al.//, 2016).
+AvrRxo1 is a phosphotransferase that produces two novel metabolites by phosphorylating nicotinamide/nicotinic acid adenine dinucleotide at the adenosine 3'-hydroxyl group. Both products of AvrRxo1, 3'-NADP and 3'-nicotinic acid adenine dinucleotide phosphate (3'-NAADP), had been used before as inhibitors or signaling molecules but were regarded as "artificial" compounds until then (Schuebel //et al.//, 2016). AvrRxo1 has weak phosphorylation activity on some other nucleotides including ATP (Scheubel //et al. //2016)
-AvrRxo1 was also found to phosphorylate NAD i//n planta//, and that its kinase catalytic sites are necessary for its toxic and resistance-triggering phenotypes (Shidore //et al.//, 2017). 3'-NADP accumulated upon transient expression of AvrRxo1 in //N. benthamiana//  and in rice leaves infected with //avrRxo1//-expressing strains of //X. oryzae//  (Shidore //et al.//, 2017).
+AvrRxo1 phosphorylates NAD //in planta//, and its kinase catalytic sites are necessary for toxicity, suppression of PAMP-triggered immunity, and activation of Rxo1-mediated resistance (Shidore //et al.//, 2017). In a metabolomic profile, 3'-NADP accumulated upon expression of AvrRxo1 in //E. coli//, yeast, //N. benthamiana//  and in rice leaves infected with //avrRxo1//-expressing strains of //X. oryzae//, suggesting that the AvrRxo1 product is not utilized or degraded by the cell (Shidore //et al.//, 2017). 3'-NADP was the only metabolite observed to accumulate in an //avrRxo1//-dependent manner, and it is not known whether NAADP is phosphorylated by AvrRxo1 //in planta //  (Shidore //et al.//, 2017).
 === Interaction partners ===
@@ Line 56: / Line 69: @@
 The gene product of the adjacent gene, AvrRxo1-ORF2 aka Arc1, binds AvrRxo1, but binding is structurally different from typical effector-binding chaperones, in that it has a distinct fold containing a novel kinase-binding domain (Han //et al.//, 2015).
-AvrRxo1 interacts with both the ubiquitin E3 ligase SINAT4 and the cysteine protease RD21A, enhancing SINAT4 activity, thus promoting the degradation of RD21A //in vivo//  (Liu //et al.//, 2020).
+AvrRxo1 interacts with the //Arabidopsis thaliana//  ubiquitin E3 ligase SINAT4 and the cysteine protease RD21A during transient expression in //N. benthamiana. //Interaction enhanced SINAT4 activity and promoted the degradation of RD21A //in vivo, //in a manner dependent on the AvrRxo1 ATP-binding motif (Liu //et al.//, 2020).
+AvrRxo1 interacts with OsPDX1.2 in a yeast two-hybrid assay and in planta, as assessed by split YFP and coIP assays (Liu //et al.//, 2022).
 ===== Conservation =====
@@ Line 64: / Line 79: @@
 Yes (e.g. //X. alfalfae//, //X. axonopodis//, //X. bromi//, //X. euvesicatoria//, //X. oryzae//, //X. translucens//).
-AvrRxo1 appears to be widely conserved in Asian strains of //Xoc// but much less present in African strains, which implies that deployment of //Rxo1//-containing varieties may not be an appropriate breeding strategy for controlling bacterial leaf streak disease in Africa (Wonni //et al.//, 2014).
+AvrRxo1 appears to be widely conserved in Asian strains of //Xoc//  but much less present in African strains, which implies that deployment of //Rxo1//-containing varieties may not be an appropriate breeding strategy for controlling bacterial leaf streak disease in Africa (Wonni //et al.//, 2014).
+AvrRxo1 is conserved in nearly all strains of //X. euvesicatoria//, but is incompletely distributed in other species surveyed (Triplett et al. 2016, Barak et al. 2016). Strains with inactivated //avrRxo1//  genes were frequently observed to harbor sequence insertions in the toxic //avrRxo1//  gene, while the toxin-protective //arc1//  gene remained intact (Triplett //et al.,//  2016).
 === In other plant pathogens/symbionts ===
-Yes (//Acidovorax// spp., //Burkholderia andropogonis//) (Triplett //et al.//, 2016).
+Yes (//Acidovorax//  spp., //Paraburkholderia andropogonis//) (Triplett //et al.//, 2016).
+Homologs of the //avrRxo1:arc1//  operon in which the avrRxo1 homolog lacks a type III secretion signal are found in other environmental microbes, including the filamentous myxobacteria //Cystobacter fuscus//  and uncultured candidate //Saccharimonas//  and //Parcubacteria//  spp. (Triplett// et al.//  2016).
+===== Conservation =====
+=== In xanthomonads ===
+Yes (e.g. //X. alfalfae//, //X. axonopodis//, //X. bromi//, //X. euvesicatoria//, //X. oryzae//, //X. translucens//).
+AvrRxo1 appears to be widely conserved in Asian strains of //Xoc//  but much less present in African strains, which implies that deployment of //Rxo1//-containing varieties may not be an appropriate breeding strategy for controlling bacterial leaf streak disease in Africa (Wonni //et al.//, 2014).
+AvrRxo1 is conserved in nearly all strains of //X. euvesicatoria//, but is incompletely distributed in other species surveyed (Triplett et al. 2016, Barak et al. 2016). Strains with inactivated //avrRxo1//  genes were frequently observed to harbor sequence insertions in the toxic //avrRxo1//  gene, while the toxin-protective //arc1//  gene remained intact (Triplett //et al.,//  2016).
+=== In other plant pathogens/symbionts ===
+Yes (//Acidovorax//  spp., //Paraburkholderia andropogonis//) (Triplett //et al.//, 2016).
+Homologs of the //avrRxo1:arc1//  operon in which the avrRxo1 homolog lacks a type III secretion signal are found in other environmental microbes, including the filamentous myxobacteria //Cystobacter fuscus//  and uncultured candidate //Saccharimonas//  and //Parcubacteria//  spp. (Triplett// et al.//  2016).
 ===== References =====
@@ Line 77: / Line 113: @@
 Liu H, Chang Q, Feng W, Zhang B, Wu T, Li N, Yao F, Ding X, Chu Z (2014). Domain dissection of AvrRxo1 for suppressor, avirulence and cytotoxicity functions. PLoS One 9: e113875. DOI: [[https://doi.org/10.1371/journal.pone.0113875|10.1371/journal.pone.0113875]]
-Liu Y, Wang K, Cheng Q, Kong D, Zhang X, Wang Z, Wang Q, Qi X, Yan J, Chu J, Ling H, Li Q, Miao J, Zhao B (2020). Cysteine protease RD21A regulated by E3 ligase SINAT4 is required for drought-induced resistance to //Pseudomonas syringae// in Arabidopsis. J. Exp. Bot., eraa255 (in press). DOI: [[https://doi.org/10.1093/jxb/eraa255|10.1093/jxb/eraa255]]
+Liu H, Lu C, Li Y, Wu T, Zhang B, Liu B, Feng W, Xu Q, Dong H, He S, Chu Z, Ding X (2022). The bacterial effector AvrRxo1 inhibits vitamin B6 biosynthesis to promote infection in rice. Plant Commun. 3: 100324. DOI: [[https://doi.org/10.1016/j.xplc.2022.100324|10.1016/j.xplc.2022.100324]]
+Liu Y, Wang K, Cheng Q, Kong D, Zhang X, Wang Z, Wang Q, Qi X, Yan J, Chu J, Ling H, Li Q, Miao J, Zhao B (2020). Cysteine protease RD21A regulated by E3 ligase SINAT4 is required for drought-induced resistance to //Pseudomonas syringae// in Arabidopsis. J. Exp. Bot. 71: 5562-5576. DOI: [[https://doi.org/10.1093/jxb/eraa255|10.1093/jxb/eraa255]]
 Popov G, Fraiture M, Brunner F, Sessa G (2016). Multiple //Xanthomonas euvesicatoria// type III effectors inhibit flg22-triggered immunity. Mol. Plant Microbe Interact. 29: 651-660. DOI: [[https://doi.org/10.1094/MPMI-07-16-0137-R|10.1094/MPMI-07-16-0137-R]]

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