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--- bacteria:t3e:avrbs2 [2023/05/22 09:20] – [References] rkoebnik
+++ bacteria:t3e:avrbs2 [2025/07/24 22:10] (current) – jfpothier
@@ Line 1: / Line 1: @@
-====== AvrBs2 ======
+====== The Type III Effector AvrBs2 from //Xanthomonas// ======
 Author: [[https://www.researchgate.net/profile/Spela_Alic|Špela Alič]]\\
 Internal reviewer: [[https://www.researchgate.net/profile/Ralf_Koebnik|Ralf Koebnik]]\\
-Expert reviewer: FIXME
 Class: AvrBs2\\
@@ Line 18: / Line 17: @@
 Indirectly – the pathovars that induced //Bs2//-mediated hypersensitivity were classified as having AvrBs2 activity (Kearney & Staskawicz, 1990).
 === (Experimental) evidence for being a T3E ===
@@ Line 25: / Line 25: @@
 Once the effector domain of AvrBs2 that is recognized by //Bs2// pepper plants was identified (Mudgett //et al.//, 2000), this knowledge was used to construct a Tn//5//-based reporter transposon, which was sucessfully used in genetic screens to isolate type III effectors from //Xanthomonas// (Roden //et al.//, 2004).
 === Regulation ===
 Transcriptome analysis (RNA-seq) and qRT-PCR have shown that //avrBs2// gene expression is downregulated in a //X. citri// pv. //citri// Δ//phoP// mutant, indicating that PhoP is a positive regulator of //avrBs2// expression (Wei //et al//., 2019).
-qRT-PCR revealed that transcript levels of 15 out of 18 tested non-TAL effector genes (as well as the regulatory genes //hrpG// and //hrpX//), including //avrBs2//, were significantly reduced in the //Xanthomonas oryzae// pv. //oryzae// Δ//xrvC// mutant compared with those in the wild-type strain PXO99<sup>A</sup>  (Liu //et al//., 2016).
+qRT-PCR revealed that transcript levels of 15 out of 18 tested non-TAL effector genes (as well as the regulatory genes //hrpG// and //hrpX//), including //avrBs2//, were significantly reduced in the //Xanthomonas oryzae// pv. //oryzae// Δ//xrvC// mutant compared with those in the wild-type strain PXO99<sup>A</sup> (Liu //et al//., 2016).
 === Phenotypes ===
-  * The loss of a functional //avrBs2//  gene was found to affect the fitness of //Xcv//  and revealed fitness costs for three additional, plasmid-borne effector genes (//avrBs1//, //avrBs3//, //avrBs4//) in //Xcv//, indicating that complex functional interactions exist among effector genes (Wichmann & Bergelson, 2004).
+  * The loss of a functional //avrBs2// gene was found to affect the fitness of //Xcv// and revealed fitness costs for three additional, plasmid-borne effector genes (//avrBs1//, //avrBs3//, //avrBs4//) in //Xcv//, indicating that complex functional interactions exist among effector genes (Wichmann & Bergelson, 2004).
-  * AvrBs2 has been demonstrated to be required for full virulence of //Xcv//, //X. oryzae//  pv. //oryzicola//, //X. phaseoli //pv. //manihotis//  (aka //X. axonopodis//  pv. //manihotis//) (Zhao //et al//., 2011; Li //et al//., 2015; Mutka //et al.//, 2016; Medina //et al//., 2018).
+  * AvrBs2 has been demonstrated to be required for full virulence of //Xcv//, //X. oryzae// pv. //oryzicola//, //X. phaseoli// pv. //manihotis// (aka //X. axonopodis// pv. //manihotis//) (Zhao //et al//., 2011; Li //et al//., 2015; Mutka //et al.//, 2016; Medina //et al//., 2018).
-  * Recognition of //AvrBs2//  by OsHRL makes rice more resistant against //X. oryzae//  pv. //oryzicola//  (Park //et al//., 2010).
+  * Recognition of //AvrBs2// by OsHRL makes rice more resistant against //X. oryzae// pv. //oryzicola// (Park //et al//., 2010).
-  * It was shown in pepper and tomato lines without //Bs2 //that mutations of catalytic residues in the glycerolphosphodiesterase did not interfere with the ability of the plant to recognize AvrBs2 through the cognate R gene //Bs2//  and trigger disease resistance. This finding suggests that recognition of AvrBs2 is independent of its glycerolphosphodiesterase enzyme activity (Zhao //et al//., 2011).
+  * It was shown in pepper and tomato lines without //Bs2// that mutations of catalytic residues in the glycerolphosphodiesterase did not interfere with the ability of the plant to recognize AvrBs2 through the cognate R gene //Bs2// and trigger disease resistance. This finding suggests that recognition of AvrBs2 is independent of its glycerolphosphodiesterase enzyme activity (Zhao //et al//., 2011).
-  * AvrBs2 contributes to //X. oryzae//  pv. //oryzicola//  virulence by suppressing PAMP-triggered defense responses in rice (Li //et al//., 2015).
+  * AvrBs2 contributes to //X. oryzae// pv. //oryzicola// virulence by suppressing PAMP-triggered defense responses in rice (Li //et al//., 2015).
-  * AvrBs2 transiently expressed in //Arabidopsis//  protoplasts suppressed flg22-induced NHO1 expression (Li //et al//., 2015).
+  * AvrBs2 transiently expressed in //Arabidopsis// protoplasts suppressed flg22-induced NHO1 expression (Li //et al//., 2015).
   * Induced expression of AvrBs2 in transgenic cell cultures was shown to dramatically suppress flg22-induced and chitin-induced immune responses, such as ROS burst and PR gene expression (Li //et al//., 2015).
-  * A ∆//xopK//  mutant strain of //Xanthomonas phaseoli//  pv. //manihotis//  showed reduced growth in planta and delayed spread through the vasculature system of cassava. Moreover, the ∆//avrBs2//  mutant strain exhibited reduced water-soaking symptoms at the site of inoculation (Mutka //et al.//, 2016).
+  * A ∆//xopK// mutant strain of //Xanthomonas phaseoli// pv. //manihotis// showed reduced growth in planta and delayed spread through the vasculature system of cassava. Moreover, the ∆//avrBs2// mutant strain exhibited reduced water-soaking symptoms at the site of inoculation (Mutka //et al.//, 2016).
   * XopN and AvrBS2 were shown to significantly contribute to virulence of //X. oryzae// pv. //oryzicola// (Xoc GX01) (Liao //et al.//, 2020).
 === Localization ===
-The //avrBs2//  gene is chromosomal (Coplin, 1989). The AvrBs2 protein is translocated from bacterial cells into the plant cytosol. Subcellular localization of AvrBs2 was demonstrated using recombinant AvrBs2::GFP reporter fusions transiently expressed in rice protoplasts. Green fluorescence of AvrBs2::GFP was detected across the entire cell. Similar subcellular localization was observed in //Nicotiana benthamiana//  (Li //et al//., 2015).
+The //avrBs2// gene is chromosomal (Coplin, 1989). The AvrBs2 protein is translocated from bacterial cells into the plant cytosol. Subcellular localization of AvrBs2 was demonstrated using recombinant AvrBs2::GFP reporter fusions transiently expressed in rice protoplasts. Green fluorescence of AvrBs2::GFP was detected across the entire cell. Similar subcellular localization was observed in //Nicotiana benthamiana// (Li //et al//., 2015).
 === Enzymatic function ===
@@ Line 52: / Line 54: @@
 === Interaction partners ===
-Gene-for-gene relationship with corresponding resistance gene //Bs2//  (Minsavage //et al//., 1990). Furthermore, interaction between AvrBs2 and OsHRL was experimentaly shown by yeast two-hybrid screening (Park //et al//., 2010).
+Gene-for-gene relationship with corresponding resistance gene //Bs2// (Minsavage //et al//., 1990). Furthermore, interaction between AvrBs2 and OsHRL was experimentaly shown by yeast two-hybrid screening (Park //et al//., 2010).
 ===== Conservation =====
@@ Line 69: / Line 71: @@
 Indirectly – the pathovars that induced //Bs2//-mediated hypersensitivity were classified as having AvrBs2 activity (Kearney & Staskawicz, 1990).
 === (Experimental) evidence for being a T3E ===
-AvrBs2 fused to the calmodulin-activated adenylate cyclase domain was shown to translocate into plant cells (cytosol), detected through rise of cAMP levels inside the plant tissue. The //hrpF// <sup>-</sup>  mutant was used as a negative control to prove the translocation process. Further it was shown that AvrBs2 contains two N-terminal secretion and translocation signals: first for secretion and the second for enhancing translocation (Casper-Lindley //et al//., 2002).
+AvrBs2 fused to the calmodulin-activated adenylate cyclase domain was shown to translocate into plant cells (cytosol), detected through rise of cAMP levels inside the plant tissue. The //hrpF//<sup>-</sup> mutant was used as a negative control to prove the translocation process. Further it was shown that AvrBs2 contains two N-terminal secretion and translocation signals: first for secretion and the second for enhancing translocation (Casper-Lindley //et al//., 2002).
 === Regulation ===
-qRT-PCR revealed that transcript levels of 15 out of 18 tested non-TAL effector genes (as well as the regulatory genes //hrpG// and //hrpX//), including //avrBs2//, were significantly reduced in the //Xanthomonas oryzae// pv. //oryzae// Δ//xrvC// mutant compared with those in the wild-type strain PXO99<sup>A</sup>  (Liu //et al//., 2016).
+qRT-PCR revealed that transcript levels of 15 out of 18 tested non-TAL effector genes (as well as the regulatory genes //hrpG// and //hrpX//), including //avrBs2//, were significantly reduced in the //Xanthomonas oryzae// pv. //oryzae// Δ//xrvC// mutant compared with those in the wild-type strain PXO99<sup>A</sup> (Liu //et al//., 2016).
 Transcriptome analysis (RNA-seq) and qRT-PCR have shown that //avrBs2// gene expression is downregulated in a //X. citri// pv. //citri// Δ//phoP// mutant, indicating that PhoP is a positive regulator of //avrBs2// expression (Wei //et al//., 2019).
 === Phenotypes ===
-  * AvrBs2 has been demonstrated to be required for full virulence of //X. euvesicatoria//  pv. //euvesicatoria//  (aka //X. campestris//  pv. //vesicatoria//), //X. oryzae//  pv. //oryzicola//, //X. phaseoli //pv. //manihotis//  (aka //X. axonopodis//  pv. //manihotis//) (Zhao //et al//., 2011; Li //et al//., 2015; Mutka //et al.//, 2016; Medina //et al//., 2018).
+  * AvrBs2 has been demonstrated to be required for full virulence of //X. euvesicatoria// pv. //euvesicatoria// (aka //X. campestris// pv. //vesicatoria//), //X. oryzae// pv. //oryzicola//, //X. phaseoli// pv. //manihotis// (aka //X. axonopodis// pv. //manihotis//) (Zhao //et al//., 2011; Li //et al//., 2015; Mutka //et al.//, 2016; Medina //et al//., 2018).
-  * Recognition of AvrBs2 by OsHRL makes rice more resistant against //X. oryzae//  pv. //oryzicola//  (Park //et al//., 2010).
+  * Recognition of AvrBs2 by OsHRL makes rice more resistant against //X. oryzae// pv. //oryzicola// (Park //et al//., 2010).
-  * It was shown in pepper and tomato lines without //Bs2 //that mutations of catalytic residues in the glycerolphosphodiesterase did not interfere with the ability of the plant to recognize AvrBs2 through the cognate R gene //Bs2//  and trigger disease resistance. This finding suggests that recognition of AvrBs2 is independent of its glycerolphosphodiesterase enzyme activity (Zhao //et al//., 2011).
+  * It was shown in pepper and tomato lines without //Bs2// that mutations of catalytic residues in the glycerolphosphodiesterase did not interfere with the ability of the plant to recognize AvrBs2 through the cognate R gene //Bs2// and trigger disease resistance. This finding suggests that recognition of AvrBs2 is independent of its glycerolphosphodiesterase enzyme activity (Zhao //et al//., 2011).
-  * AvrBs2 contributes to //X. oryzae//  pv. //oryzicola//  virulence by suppressing PAMP-triggered defense responses in rice (Li //et al//., 2015).
+  * AvrBs2 contributes to //X. oryzae// pv. //oryzicola// virulence by suppressing PAMP-triggered defense responses in rice (Li //et al//., 2015).
-  * AvrBs2 transiently expressed in //Arabidopsis//  protoplasts suppressed flg22-induced NHO1 expression (Li //et al//., 2015).
+  * AvrBs2 transiently expressed in //Arabidopsis// protoplasts suppressed flg22-induced NHO1 expression (Li //et al//., 2015).
   * Induced expression of AvrBs2 in transgenic cell cultures was shown to dramatically suppress flg22-induced and chitin-induced immune responses, such as ROS burst and PR gene expression (Li //et al//., 2015).
-  * A ∆//xopK//  mutant strain of //Xanthomonas phaseoli//  pv. //manihotis//  (aka //Xanthomonas axonopodis//  pv. //manihotis//) showed reduced growth in planta and delayed spread through the vasculature system of cassava. Moreover, the ∆avrBs2 mutant strain exhibited reduced water-soaking symptoms at the site of inoculation (Mutka //et al.//, 2016).
+  * A ∆//xopK// mutant strain of //Xanthomonas phaseoli// pv. //manihotis// (aka //Xanthomonas axonopodis// pv. //manihotis//) showed reduced growth in planta and delayed spread through the vasculature system of cassava. Moreover, the ∆avrBs2 mutant strain exhibited reduced water-soaking symptoms at the site of inoculation (Mutka //et al.//, 2016).
-  * //Agrobacterium//-mediated transient expression of both XopQ and XopX in rice cells resulted in induction of rice immune responses, which were not observed when either protein was individually expressed. A screen for //Xanthomonas//  effectors which can suppress XopQ-XopX induced rice immune responses, led to the identification of five effectors, namely XopU, XopV, XopP, XopG and AvrBs2, that could individually suppress these immune responses. These results suggest a complex interplay of //Xanthomonas//  T3SS effectors in suppression of both pathogen-triggered immunity and effector-triggered immunity to promote virulence on rice (Deb //et al.//, 2020).
+  * //Agrobacterium//-mediated transient expression of both XopQ and XopX in rice cells resulted in induction of rice immune responses, which were not observed when either protein was individually expressed. A screen for //Xanthomonas// effectors which can suppress XopQ-XopX induced rice immune responses, led to the identification of five effectors, namely XopU, XopV, XopP, XopG and AvrBs2, that could individually suppress these immune responses. These results suggest a complex interplay of //Xanthomonas// T3SS effectors in suppression of both pathogen-triggered immunity and effector-triggered immunity to promote virulence on rice (Deb //et al.//, 2020).
 === Localization ===
-The //avrBs2//  gene is chromosomal (Coplin, 1989). The AvrBs2 protein is translocated from bacterial cells into the plant cytosol. Subcellular localization of AvrBs2 was demonstrated using recombinant AvrBs2::GFP reporter fusions transiently expressed in rice protoplasts. Green fluorescence of AvrBs2::GFP was detected across the entire cell. Similar subcellular localization was observed in //Nicotiana benthamiana//  (Li //et al//., 2015).
+The //avrBs2// gene is chromosomal (Coplin, 1989). The AvrBs2 protein is translocated from bacterial cells into the plant cytosol. Subcellular localization of AvrBs2 was demonstrated using recombinant AvrBs2::GFP reporter fusions transiently expressed in rice protoplasts. Green fluorescence of AvrBs2::GFP was detected across the entire cell. Similar subcellular localization was observed in //Nicotiana benthamiana// (Li //et al//., 2015).
 === Enzymatic function ===
@@ Line 97: / Line 102: @@
 === Interaction partners ===
-Gene-for-gene relationship with corresponding resistance gene //Bs2//  (Minsavage //et al//., 1990). Furthermore, interaction between AvrBs2 and OsHRL was experimentaly shown by yeast two-hybrid screening (Park //et al//., 2010).
+Gene-for-gene relationship with corresponding resistance gene //Bs2// (Minsavage //et al//., 1990). Furthermore, interaction between AvrBs2 and OsHRL was experimentaly shown by yeast two-hybrid screening (Park //et al//., 2010).
 ===== Conservation =====
@@ Line 103: / Line 108: @@
 === In xanthomonads ===
-Yes (//e.g.//, //X//. //arboricola//, //X//. //campestris//, //X//. //citri//, //X. euvesicatoria//, //X//. //fuscans//, //X. oryzae//, //X//. //phaseoli//).
+Yes (//e.g.//, //X//. //arboricola//, //X//. //campestris//, //X//. //citri//, //X//. //euvesicatoria//, //X//. //fuscans//, //X//. //oryzae//, //X//. //phaseoli//).
+Field strains of //X//. //euvesicatoria// pv. //euvesicatoria// and //X//. //campestris// pv. //campestris// were found to accumulate mutations in the //avrBs2/////avrRxc1/3// gene in order to overcome //Bs2/////Rxc1/////Rxc3//-mediated resistance (Swords //et al.//, 1996; Gassmann //et al.//, 2000; Ignatov //et al.//, 2002). Yet, the global //Xcv// population was found to be extremely clonal, with very little genetic variation throughout the chromosome, including //avrBs2// and the plasmid-borne //avrBs1//, a finding that is consistent with recent evolution or population expansion of the species (Wichmann //et al.//, 2005).
-Field strains of //X. euvesicatoria// pv. //euvesicatoria// and //X//. //campestris// pv. //campestris// were found to accumulate mutations in the //avrBs2/////avrRxc1/3// gene in order to overcome //Bs2/////Rxc1/////Rxc3//-mediated resistance (Swords //et al.//, 1996; Gassmann //et al.//, 2000; Ignatov //et al.//, 2002). Yet, the global //Xcv// population was found to be extremely clonal, with very little genetic variation throughout the chromosome, including //avrBs2// and the plasmid-borne //avrBs1//, a finding that is consistent with recent evolution or population expansion of the species (Wichmann //et al.//, 2005).
 === In other plant pathogens/symbionts ===
@@ Line 118: / Line 124: @@
 Coplin DL (1989). Plasmids and their role in the evolution of plant pathogenic bacteria. Ann. Rev. Phytopathol. 27: 187-212. DOI: [[https://doi.org/10.1146/annurev.py.27.090189.001155|10.1146/annurev.py.27.090189.001155]]
-Deb S, Ghosh P, Patel HK, Sonti RV (2020). Interaction of the //Xanthomonas// effectors XopQ and XopX results in induction of rice immune responses. Plant J., in press. DOI: [[https://doi.org/10.1111/tpj.14924|10.1111/tpj.14924]]
+Deb S, Ghosh P, Patel HK, Sonti RV (2020). Interaction of the //Xanthomonas// effectors XopQ and XopX results in induction of rice immune responses. Plant J. 104: 332-350. DOI: [[https://doi.org/10.1111/tpj.14924|10.1111/tpj.14924]]
 Gassmann W, Dahlbeck D, Chesnokova O, Minsavage GV, Jones JB, Staskawicz BJ (2000). Molecular evolution of virulence in natural field strains of //Xanthomonas campestris// pv. //vesicatoria//. J. Bacteriol. 182: 7053-7059. DOI: [[https://doi.org/10.1128/jb.182.24.7053-7059.2000|10.1128/jb.182.24.7053-7059.2000]]
@@ Line 126: / Line 132: @@
 Habyarimana F, Ahmer BM (2013). More evidence for secretion signals within the mRNA of type 3 secreted effectors. J. Bacteriol. 195: 2117-2118. DOI: [[https://doi.org/10.1128/JB.00303-13|10.1128/JB.00303-13]]
-Ignatov AN, Monakhos GF, Dzhalilov FS, Pozmogova GV (2002). Avirulence gene from //Xanthomonas campestris //pv. //campestris// homologous to the //avrBs2// locus is recognized in race-specific reaction by two different resistance genes in Brassicas. Genetika 38: 1656-1662 [Article in Russian] / Russian J. Genet. 38: 1404-1410. DOI: [[https://doi.org/10.1023/A:1021643907032|10.1023/A:1021643907032]]
+Ignatov AN, Monakhos GF, Dzhalilov FS, Pozmogova GV (2002). Avirulence gene from //Xanthomonas campestris// pv. //campestris// homologous to the //avrBs2// locus is recognized in race-specific reaction by two different resistance genes in Brassicas. Genetika 38: 1656-1662 [Article in Russian] / Russian J. Genet. 38: 1404-1410. DOI: [[https://doi.org/10.1023/A:1021643907032|10.1023/A:1021643907032]]
 Kearney B, Staskawicz BJ (1990). Widespread distribution and fitness contribution of //Xanthomonas campestris// avirulence gene //avrBs2//. Nature 346: 385-386. DOI: [[https://doi.org/10.1038/346385a0|10.1038/346385a0]]
@@ Line 160: / Line 166: @@
 ===== Further reading =====
-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]]. Corrected in: Phytopathology (2019) 109: 1820. DOI: [[https://doi.org/10.1094/PHYTO-03-16-0119.1-FI|10.1094/PHYTO-03-16-0119.1-FI]]
+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]]. Corrected in: Phytopathology (2019) 109: 1820. DOI: [[https://doi.org/10.1094/PHYTO-03-16-0119.1-FI|10.1094/PHYTO-03-16-0119.1-FI]]
+===== Acknowledgements =====
+This fact sheet is based upon work from COST Action CA16107 EuroXanth, supported by COST (European Cooperation in Science and Technology).

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