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--- bacteria:t3e:xopj2 [2020/07/08 17:26]
rkoebnik [Biological function]
+++ bacteria:t3e:xopj2 [2020/08/11 14:43] (current)
rkoebnik
@@ Line 2: / Line 2: @@
 Author: [[https://www.researchgate.net/profile/Daiva_Burokiene|Daiva Burokienė]]\\
-Internal reviewer: FIXME \\
+Internal reviewer: [[https://www.researchgate.net/profile/Eran_Bosis|Eran Bosis]]\\
 Expert reviewer: FIXME
-Class: XopJ2 (//syn.// AvrBsT) Family: XopJ2 Prototype: AvrBsT (//Xanthomonas euvesicatoria// pv. //euvesicatoria//, aka //Xanthomonas campestris// pv. //vesicatoria// [//Xcv//]; strain 75-3)\\
+Class: XopJ\\
+Family: XopJ2\\
+Prototype: AvrBsT (//Xanthomonas euvesicatoria// pv. //euvesicatoria//, ex //Xanthomonas campestris// pv. //vesicatoria//; strain 75-3)\\
 RefSeq ID: [[https://www.ncbi.nlm.nih.gov/protein/WP_074052319.1|WP_074052319.1]] (350 aa)\\
-D structure: not available
+Synonym: AvrBsT\\
+D structure: unknown
 ===== Biological function =====
@@ Line 16: / Line 19: @@
 === (Experimental) evidence for being a T3E ===
-C-myc epitope-tagged AvrBsT protein was detected in culture supernatants of the //Xcv// strain 85* only in the presence of a functional type III apparatus and not in a //hrcV// mutant, showing that the protein is secreted in an hrp-dependent manner (Escolar //et al//., 2001). Transient expression of //avrBsT// in resistant host plants using //Agrobacterium tumefaciens//-mediated gene transfer resulted in the induction of a specific HR. This indicates that recognition occurs intracellularly, and suggested that during the Xcv infection, AvrBsT is translocated from //Xcv// into the plant cell (Escolar //et al//., 2001). Mutation studies of a putative translocation motif (TrM) showed that the proline/arginine-rich motif contributes to efficient type III-dependent secretion and translocation of AvrBsT and affects the dependence of AvrBsT transport on the general T3S chaperone HpaB (Prochaska //et al//., 2018).
+C-myc epitope-tagged AvrBsT protein was detected in culture supernatants of the //X. campestris// pv. //vesicatoria// (//Xcv//) strain 85* only in the presence of a functional type III apparatus and not in a //hrcV// mutant, showing that the protein is secreted in an hrp-dependent manner (Escolar //et al//., 2001). Transient expression of //avrBsT// in resistant host plants using //Agrobacterium tumefaciens//-mediated gene transfer resulted in the induction of a specific HR. This indicates that recognition occurs intracellularly, and suggested that during the Xcv infection, AvrBsT is translocated from //Xcv// into the plant cell (Escolar //et al//., 2001). Mutation studies of a putative translocation motif (TrM) showed that the proline/arginine-rich motif contributes to efficient type III-dependent secretion and translocation of AvrBsT and affects the dependence of AvrBsT transport on the general T3S chaperone HpaB (Prochaska //et al//., 2018).
 === Regulation ===
@@ Line 29: / Line 32: @@
   * Resistance in Pi-0 was found to be caused by a recessive mutation predicted to inactivate a carboxylesterase known to hydrolyze lysophospholipids and acylated proteins in eukaryotes. Transgenic Pi-0 plants expressing the wild-type allele from the //A. thaliana//  ecotype Columbia were susceptible to //Pst//  DC3000 AvrRpt2-AvrBsT-HA infection. These data indicated that the carboxylesterase inhibits AvrBsT-triggered phenotypes in //Arabidopsis//, and the resistance gene was therefore called //SOBER1//  (Suppressor Of AvrBsT-Elicited Resistance 1), where the inactive allele in Pi-0, //sober1-1//, provides resistance (Cunnac //et al//., 2007).
   * It was later shown that Pi-0 leaves infected with //Pst//  DC3000 expressing AvrBsT accumulated higher levels of phosphatidic acid (PA) compared to leaves infected with //Pst//  DC3000. Phospholipase D (PLD) activity was required for high PA levels and AvrBsT-dependent HR in Pi-0. Overexpression of SOBER1 in Pi-0 reduced PA levels and inhibited HR. These data implicated PA, phosphatidylcholine (PC) and lysophosphatidylcholine (LysoPC) as potential SOBER1 substrates. Recombinant His<sub>6</sub>-SOBER1 hydrolyzed PC but not PA or LysoPC in vitro indicating that the enzyme has phospholipase A2 (PLA2) activity. Chemical inhibition of PLA2 activity in leaves expressing SOBER1 resulted in HR in response to Pst DC3000 AvrBsT. These data were consistent with the model that SOBER1 PLA2 activity suppresses PLD-dependent production of PA in response to AvrBsT elicitation (Kirik //et al//., 2009).
-  * Transgenic //Arabidopsis//  plants overexpression AvrBsT upon dexamethasone (DEX) induction showed reduced susceptibility to infection with the obligate biotrophic oomycete //Hyaloperonospora arabidopsidis//  (Hwang //et al//., 2012). In contrast, overexpression dexamethasone //(DEX)//://avrBsT//  plants exhibited enhanced susceptibility to //Pseudomonas syringae//  pv. //tomato//  (Pst) DC3000 infection (Hwang //et al//., 2012). Thus, AvrBsT overexpression leads to both disease and defense responses to microbial pathogens of different lifestyles (Hwang //et al//., 2012).
+  * Transgenic //Arabidopsis//  plants overexpression AvrBsT upon dexamethasone (DEX) induction showed reduced susceptibility to infection with the obligate biotrophic oomycete //Hyaloperonospora arabidopsidis//  (Hwang //et al//., 2012). In contrast, plants overexpressing dexamethasone //(DEX)//://avrBsT//  exhibited enhanced susceptibility to //Pseudomonas syringae//  pv. //tomato//  (Pst) DC3000 infection (Hwang //et al//., 2012). Thus, AvrBsT overexpression leads to both disease and defense responses to microbial pathogens of different lifestyles (Hwang //et al//., 2012).
   * Phylogenomics revealed that a host-range expansion of //X. euvesicatoria//  pv. //perforans//  (//Xep//) field strains on pepper is due, in part, to a loss of the effector AvrBsT. Further studies with //Xep//  demonstrated that a double deletion of //avrBsT//  and //xopQ//  allowed a host range expansion for //Nicotiana benthamiana//  (Schwartz //et al//., 2015).
   * Later, AvrBsT was found to contribute to fitness of //Xep//  on tomato plants under field conditions (Abrahamian //et al//., 2018).
@@ Line 39: / Line 42: @@
 === Enzymatic function ===
-AvrBsT belongs to the YopJ family, members of which were shown to act as cysteine proteases, which contain a catalytic triad (His, Glu, Cys). It was shown that AvrBsT requires a functional protease catalytic core to trigger defense responses in resistant plant cells, suggesting that AvrBsT acts as a protease to disrupt immune signaling pathways (Orth //et al//., 2000). AvrBsT was later shown to possess acetyltransferase activity and acetylates ACIP1 (for //ACETYLATED INTERACTING PROTEIN1//) from //Arabidopsis//. Genetic studies revealed that //Arabidopsis//  ACIP family members are required for both pathogen-associated molecular pattern (PAMP)-triggered immunity and AvrBsT-triggered ETI during //Pst//  DC3000 infection. Microscopy studies revealed that ACIP1 is associated with punctae on the cell cortex and some of these punctae co-localize with microtubules. Wild-type //Pst//  DC3000 or //Pst//  DC3000 AvrRpt2 infection triggered the formation of numerous, small ACIP1 punctae and rods. By contrast, //Pst//  DC3000 AvrBsT infection primarily triggered the formation of large GFP-ACIP1 aggregates, in an acetyltransferase-dependent manner. These data suggested that AvrBsT-dependent acetylation //in planta//  alters ACIP1’s defense function, which is linked to the activation of ETI (Cheong //et al//., 2014).
+AvrBsT belongs to the YopJ family, members of which were shown to act as cysteine proteases containing a catalytic triad (His, Glu, Cys). It was shown that AvrBsT requires a functional protease catalytic core to trigger defense responses in resistant plant cells, suggesting that AvrBsT acts as a protease to disrupt immune signaling pathways (Orth //et al//., 2000). AvrBsT was later shown to possess acetyltransferase activity and acetylates ACIP1 (for //ACETYLATED INTERACTING PROTEIN1//) from //Arabidopsis//. Genetic studies revealed that //Arabidopsis//  ACIP family members are required for both pathogen-associated molecular pattern (PAMP)-triggered immunity and AvrBsT-triggered ETI during //Pst//  DC3000 infection. Microscopy studies revealed that ACIP1 is associated with punctae on the cell cortex and some of these punctae co-localize with microtubules. Wild-type //Pst//  DC3000 or //Pst//  DC3000 AvrRpt2 infection triggered the formation of numerous, small ACIP1 punctae and rods. By contrast, //Pst//  DC3000 AvrBsT infection primarily triggered the formation of large GFP-ACIP1 aggregates, in an acetyltransferase-dependent manner. These data suggested that AvrBsT-dependent acetylation //in planta//  alters ACIP1’s defense function, which is linked to the activation of ETI (Cheong //et al//., 2014).
 === Interaction partners ===
   * Yeast two-hybrid based analyses identified a putative regulator of sugar metabolism, SNF1-related kinase 1 (SnRK1), as an interactor of AvrBsT (Szczesny //et al//., 2010). Gene silencing experiments revealed that SnRK1 is required for the induction of the AvrBs1-specific HR, which is suppressed by AvrBsT (Szczesny //et al//., 2010). Thus, SnRK1 may be involved in the AvrBsT-mediated suppression of the AvrBs1-specific HR (Szczesny //et al//., 2010).
-  * Later, the pepper SGT1 (for suppressor of the G2 allele of //skp1//) and PIK1 (for receptor-like cytoplasmic kinase1) were identified as a host interactor of AvrBsT. SGT1 forms a heterotrimeric complex with both AvrBsT and PIK1 exclusively in the cytoplasm. PIK1 specifically phosphorylates SGT1 and AvrBsT in vitro. AvrBsT binding to SGT1 resulted in the inhibition of PIK1-mediated SGT1 phosphorylation and subsequent nuclear transport of the SGT1-PIK1 complex (Kim //et al//., 2014).
+  * Later, the pepper SGT1 (for suppressor of the G2 allele of //skp1//) and PIK1 (for receptor-like cytoplasmic kinase1) were identified as host interactors of AvrBsT. SGT1 forms a heterotrimeric complex with both AvrBsT and PIK1 exclusively in the cytoplasm. PIK1 specifically phosphorylates SGT1 and AvrBsT in vitro. AvrBsT binding to SGT1 resulted in the inhibition of PIK1-mediated SGT1 phosphorylation and subsequent nuclear transport of the SGT1-PIK1 complex (Kim //et al//., 2014).
   * Using a yeast two-hybrid screen, the pepper CaHSP70a was identified as another AvrBsT-interacting protein. Bimolecular fluorescence complementation and co-immunoprecipitation assays confirmed the specific interaction between CaHSP70a and AvrBsT //in planta//  (Kim //et al//., 2015a).
   * Using a yeast two-hybrid screen, the pepper aldehyde dehydrogenase 1 (CaALDH1) was identified as another AvrBsT-interacting protein. Bimolecular fluorescence complementation and co-immunoprecipitation assays confirmed the interaction between CaALDH1 and AvrBsT //in planta//  (Kim //et al//., 2015b).
@@ Line 57: / Line 60: @@
 Yes (//Acidovorax//  spp., //Brenneria//  spp., //Erwinia//  spp., //Pseudomonas//  spp., //Ralstonia//  spp.).
+=====   =====
 ===== References =====
@@ Line 93: / Line 98: @@
 Szczesny R, Büttner D, Escolar L, Schulze S, Seiferth A, Bonas U (2010). Suppression of the AvrBs1-specific hypersensitive response by the YopJ effector homolog AvrBsT from //Xanthomonas//  depends on a SNF1-related kinase. New Phytol. 187: 1058-1074. DOI: [[https://doi.org/10.1111/j.1469-8137.2010.03346.x|10.1111/j.1469-8137.2010.03346.x]]
+===== Further reading =====
+Han SW, Hwang BK (2017). Molecular functions of //Xanthomonas//  type III effector AvrBsT and its plant interactors in cell death and defense signaling. Planta 245: 237-253. DOI: [[https://doi.org/10.1007/s00425-016-2628-x|10.1007/s00425-016-2628-x]]
+Timilsina S, Abrahamian P, Potnis N, Minsavage GV, White FF, Staskawicz BJ, Jones JB, Vallad GE, Goss EM (2016). Analysis of sequenced genomes of Xanthomonas perforans identifies candidate targets for resistance breeding in tomato. Phytopathology 106: 1097-1104. DOI: [[https://doi.org/10.1094/PHYTO-03-16-0119-FI|10.1094/PHYTO-03-16-0119-FI]]

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