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--- bacteria:t3e:avrbs3 [2020/08/07 13:51]
jensboch
+++ bacteria:t3e:avrbs3 [2020/11/30 13:33] (current)
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 Author: [[https://www.researchgate.net/profile/Nay_Dia2|Nay C. Dia]]\\
-Internal reviewer: Jens Boch\\
+Internal reviewer: [[https://www.genetik.uni-hannover.de/boch.html|Jens Boch]]\\
-Expert reviewer: FIXME
+Expert reviewer: [[https://www.researchgate.net/profile/Sabine_Thieme3|Sabine Thieme]]
 Class: AvrBs3\\
@@ Line 18: / Line 18: @@
 === (Experimental) evidence for being a T3E ===
-AvrBs3 is secreted and translocated into the plant via the Hrp type III secretion system (Bonas //et al//., 1991; Van den Ackerveken //et al//., 1996; Bonas //et al//., 1999). In contrast to wild-type bacteria, an //Xcv// mutant carrying a deletion in the conserved //hrp// gene //hrcV// did not secrete AvrBs3 indicating that AvrBs3 is transported by the Hrp system (Rossier //et al//., 1999). In its C-terminal domain, AvrBs3 carries an acidic activation domain which is functional in plant cells (Van den Ackerveken //et al//., 1996). Two nuclear localization signals in the C-terminal domain of AvrBs3 facilitate transport into the plant cell nucleus (Van den Ackerveken //et al//., 1996; Szurek //et al//., 2002). These eukaryotic features support the role of AvrBs3 and members of the TALE family within the eukaryotic host cell.
+AvrBs3 is secreted and translocated into the plant via the Hrp type III secretion system (Bonas //et al//., 1991; Van den Ackerveken //et al//., 1996; Bonas //et al//., 1999). In contrast to wild-type bacteria, an //Xcv// mutant carrying a deletion in the conserved //hrp// gene //hrcV// did not secrete AvrBs3 indicating that AvrBs3 is transported by the Hrp system (Rossier //et al//., 1999). The first 10 and 50 amino acids of AvrBs3 are required for secretion and translocation, respectively (Scheibner //et al//., 2017). In its C-terminal domain, AvrBs3 carries an acidic activation domain which is functional in plant cells (Van den Ackerveken //et al//., 1996). Two nuclear localization signals in the C-terminal domain of AvrBs3 facilitate transport into the plant cell nucleus (Van den Ackerveken //et al//., 1996; Szurek //et al//., 2002). These eukaryotic features support the role of AvrBs3 and members of the TALE family within the eukaryotic host cell.
 === Regulation ===
@@ Line 24: / Line 24: @@
 === Phenotypes ===
-The central region of the //avrBs3// gene consists of 17.5 nearly identical 102 bp repeats. Each repeat encodes 34 amino acids (Bonas //et al//., 1989).
+AvrBs3, as well as other members of the TALE family, function as specific transcription factors in plant cells. These proteins bind to specific sequences in promoters and induce expression of downstream genes. The DNA-binding specificity is encoded in the order of individual 34-amino acid repeats which each recognize one DNA base. Different TALEs typically contain different repeats and accordingly bind to different DNA sequences and target different host genes. The contributions of individual TALEs to virulence can thus be quite diverse.
-Expression analysis using gene promoter fusion and western blot analysis demonstrated that //avrBs3// was expressed and resulted in a 122 kDa protein (1164 aa) which was detectable using a specific polyclonal antibody (Bonas //et al//., 1989). AvrBs3 binds to the promotor of its target genes and activates their transcription. Differential cDNA analysis from pepper plants infected with //Xcv// with or without AvrBs3 led to the discovery of //upa// (upregulated by AvrBs3) genes whose expression is induced by AvrBs3. These //upa// genes all share a conserved promoter element, known as the //UPA// box (Kay //et al.//, 2007). //upa20// act as a master regulator of cell enlargement causing the hypertrophy symptoms associated with AvrBs3. Silencing of //upa20// decreased cell hypertrophy in infected plants while the expression of //upa20// led to hypertrophy in uninfected plants (Kay //et al//., 2007). The promoter of //Bs3// contains the //UPA// box that is bound by AvrBs3 resulting in the transcription of gene //Bs3//. //Bs3// encodes a protein that is homologous to flavine-dependent mono-oxygenases. The N‐terminal repeats in AvrBs3 correspond to the 5′‐end of the UPA box, and the C‐terminal repeats of AvrBs3 correspond to the 3′‐end of the UPA box (Boch //et al//., 2009; Moscou & Bogdanove, 2009). Repeat variable di-residues (RVDs) at positions 12 and 13 determine the specificity of each repeat, thus elucidating how AvrBs3 and other TALEs bind to DNA (Boch //et al//., 2009; Moscou & Bogdanove, 2009, Herbers //et al//., 1992; Lee //et al//., 2013). The activity of the protein is also dependent on nuclear localization signals (NLSs) and the acidic activation domain. Using a green fluorescent protein fusion in the NLSs of AvrBs3, it was shown that the dimerization takes place specifically in the cytoplasm of the plant before being transported into the nucleus (Gürlebeck //et al//., 2005).
+Expression analysis using gene promoter fusion and western blot analysis demonstrated that //avrBs3// was expressed and resulted in a 122 kDa protein (1164 aa) which was detectable using a specific polyclonal antibody (Bonas //et al//., 1989). The AvrBs3 effector protein elicits two different types of responses in resistant or susceptible plants. In susceptible pepper plants (Early Cal Wonder; ECW), hypertrophy (i.e. enlargement of mesophyll cells) is triggered by AvrBs3 (Bonas //et al//., 1989; Bonas //et al//., 1991; Marois //et al//., 2002). //Agrobacterium// strains carrying a vector with //avrBs3// induced pustules (hypertrophy) 4-5 dpi in various solanaceous plants including //Nicotiana// //clevelandii//, //N.// //benthamiana//, //N.// //tabacum//, //Petunia hybrida//, //Physalis alkekengi//, //Solanum americanum// and potato (//S.// //tuberosum//), whereas //Agrobacterium// strains carrying an empty vector did not cause any changes in inoculated plants (Marois //et al//., 2002; Kay //et al//., 2007). Differential cDNA analysis from susceptible pepper plants infected with //Xcv// with or without AvrBs3 led to the discovery of //upa// (upregulated by AvrBs3) genes whose expression is induced by AvrBs3 (Marois //et al.//, 2002; Kay //et al//., 2007). These //UPA// genes all share a conserved promoter element, known as the //UPA// box (Kay //et al.//, 2007). //UPA20// acts as a master regulator of cell enlargement causing the hypertrophy symptoms associated with AvrBs3. Silencing of //UPA20// decreased cell hypertrophy in infected plants while the expression of //UPA20// led to hypertrophy in uninfected plants (Kay //et al//., 2007).
-The AvrBs3 effector protein elicits two different types of responses in resistant or susceptible plants. Gene //Bs3// was introduced into the ECW background to generate near-isogenic line resistant ECW-30R (Bonas //et al//., 1989; Bonas //et al//., 1991). ECW-30R was inoculated using different //Xcv// strains. //Xcv// lines 71-21 and 82-8 induces a hypersensitive response HR in ECW-30R, leading to programmed cell death and thus preventing the spread of the pathogen (Bonas //et al//., 1989; Bonas //et al//., 1991). Different //Xcv// strains were inoculated on susceptible (Early Cal Wonder; ECW) pepper plants. Hypertrophy (i.e. enlargement of mesophyll cells) was observed (Bonas //et al//., 1989; Bonas //et al//., 1991; Kay //et al//., 2007; Marois //et al//., 2002). It was also speculated that this hypertrophy facilitated bacterial colonization (Kay //et al//., 2007). //Agrobacterium// strains carrying a vector with //avrBs3// induced pustules 4-5 dpi in //Nicotiana// //clevelandii//, //N.// //benthamiana//, //N.// //tabacum//, and in potato (//Solanum// //tuberosum//), whereas //Agrobacterium// strains carrying an empty vector did not cause any changes in inoculated plants (Marois //et al//., 2002).
+In resistant pepper plants, the promoter of //Bs3// contains a //UPA// box that is bound by AvrBs3 resulting in the transcription of the gene //Bs3//. //Bs3// encodes a protein that is homologous to flavine-dependent mono-oxygenases (Römer //et al//., 2007) and its expression causes rapid cell death thus preventing the spread of the pathogen (Bonas //et al//., 1989; Bonas //et al//., 1991).
+The central region of the //avrBs3// gene consists of 17.5 nearly identical 102 bp repeats. Each repeat encodes 34 amino acids (Bonas //et al//., 1989). Repeat variable di-residues (RVDs) at positions 12 and 13 determine the specificity of each repeat (Boch //et al//., 2009; Moscou & Bogdanove, 2009). Rearranging individual repeats enables construction of any desired DNA-binding specificity (Boch //et al.//, 2009).
 === Localization ===
 The //avrBs3// gene is localized on pXV11, a self-transmissible plasmid, and was initially isolated from //Xcv// strain 71-21 (Bonas //et al//., 1989). Using complementation of //Xcv// strain 85-10 (virulent on pepper ECW-30R), a 5-kb fragment including //avrBs3// was discovered (Bonas //et al//., 1989).
-=== Enzymatic function ===
+=== Molecular function ===
 DNA-binding protein. Transcriptional activator.
@@ Line 38: / Line 40: @@
 === Interaction partners ===
-Importin alpha (Szurek //et al.//, 2001) interacts with the nuclear localization sequences of AvrBs3. The basal transcription factor IIA, gamma subunit from rice interacts with a region in the C-terminal domain of TALEs (Yuan //et al//., 2016) and similar interactions might be possible for AvrBs3, too. AvrBs3 and the TALE-family of effectors bind to DNA (Kay //et al//., 2007; Römer //et al//., 2007) with their N-terminal domain exhibiting general DNA-binding properties (Gao //et al.//, 2012) and the repeat region facilitating specific interaction to DNA bases (Boch //et al//., 2009; Moscou and Bogdanove, 2009).
+Importin alpha (Szurek //et al.//, 2001) interacts with the nuclear localization sequences of AvrBs3. The basal transcription factor IIA, gamma subunit from rice interacts with a region in the C-terminal domain of TALEs (Yuan //et al//., 2016) and similar interactions might be possible for AvrBs3, too. AvrBs3 and the TALE-family of effectors bind to DNA (Kay //et al//., 2007; Römer //et al//., 2007) with their N-terminal domain exhibiting general DNA-binding properties (Gao //et al.//, 2012) and the repeat region facilitating specific interaction to DNA bases (Boch //et al//., 2009; Moscou & Bogdanove, 2009).
 ===== Conservation =====
 === In xanthomonads ===
-Yes in many pathovars, but not necesssarily all strains within a pathovar.
+Yes, in many pathovars, but not necesssarily all strains within a pathovar.
 === In other plant pathogens/symbionts ===
@@ Line 71: / Line 73: @@
 Gao H, Wu X, Chai J, Han Z (2012). Crystal structure of a TALE protein reveals an extended N-terminal DNA binding region. Cell Res. 22: 1716-1720. DOI: [[https://doi.org/10.1038/cr.2012.156|10.1038/cr.2012.156]]
-Gürlebeck D, Szurek B, Bonas U (2005). Dimerization of the bacterial effector protein AvrBs3 in the plant cell cytoplasm prior to nuclear import. Plant J. 42: 175-187. DOI: [[https://doi.org/10.1111/j.1365-313X.2005.02370.x|10.1111/j.1365-313X.2005.02370.x]]
 Herbers K, Conrads-Strauch J, Bonas U (1992). Race-specificity of plant resistance to bacterial spot disease determined by repetitive motifs in a bacterial avirulence protein. Nature 356: 172-174. DOI: [[https://doi.org/10.1038/356172a0|10.1038/356172a0]]
@@ Line 79: / Line 79: @@
 Hopkins CM, White FF, Choi SH, Guo A, Leach JE (1992). Identification of a family of avirulence genes from //Xanthomonas// //oryzae// pv. //oryzae//. Mol. Plant Microbe Interact. 5: 451-459. DOI: [[https://doi.org/10.1094/mpmi-5-451|10.1094/mpmi-5-451]]
-Ji ZY, Xiong L, Zou LF, Li YR, Ma WX, Liu L, Zakria M, Ji GH, Chen GY (2014). AvrXa7-Xa7 mediated defense in rice can be suppressed by transcriptional activator-like effectors TAL6 and TAL11a from //Xanthomonas oryzae// pv. //oryzicola//. Mol. Plant Microbe Interact. 27: 983-995. DOI: [[https://doi.org/10.1094/MPMI-09-13-0279-R|10.1094/MPMI-09-13-0279-R]]. **Retraction in: Mol. Plant Microbe Interact. (2014) 27: 1413.** FIXME
 Kay S, Hahn S, Marois E, Hause G, Bonas U (2007). A bacterial effector acts as a plant transcription factor and induces a cell size regulator. Science 318: 648-651. DOI: [[http://dx.doi.org/10.1126/science.1144956|10.1126/science.1144956]]
@@ Line 87: / Line 85: @@
 Lackner G, Moebius N, Partida-Martinez LP, Boland S, Hertweck C (2011). Evolution of an endofungal lifestyle: Deductions from the //Burkholderia rhizoxinica// genome. BMC Genomics 12: 210. DOI: [[https://doi.org/10.1186/1471-2164-12-210|10.1186/1471-2164-12-210]]
-Lee AHY, Middleton MA, Guttman DS, Desveaux D (2013). Phytopathogen type III effectors as probes of biological systems. Microb. Biotech. 6: 230-240. DOI: [[https://doi.org/10.1111/1751-7915.12042|10.1111/1751-7915.12042]]
 Mak AN, Bradley P, Cernadas RA, Bogdanove AJ, Stoddard BL (2012). The crystal structure of TAL effector PthXo1 bound to its DNA target. Science 335: 716-719. DOI: [[https://doi.org/10.1126/science.1216211|10.1126/science.1216211]]
@@ Line 104: / Line 100: @@
 Rossier O, Wengelnik K, Hahn K, Bonas U (1999). The //Xanthomonas// Hrp type III system secretes proteins from plant and mammalian bacterial pathogens. Proc. Natl. Acad. Sci. USA 96: 9368-9373. DOI: [[https://doi.org/10.1073/pnas.96.16.9368|10.1073/pnas.96.16.9368]]
-Scheibner F, Marillonnet S, Büttner D (2017). The TAL effector AvrBs3 from //Xanthomonas campestris// pv. //vesicatoria// contains multiple export signals and can enter plant cells in the absence of the type III secretion translocon. Front Microbiol. 8: 2180. DOI: [[https://doi.org/10.3389/fmicb.2017.02180|10.3389/fmicb.2017.02180]] FIXME  Information needs to be added to the profil!
+Scheibner F, Marillonnet S, Büttner D (2017). The TAL effector AvrBs3 from //Xanthomonas campestris// pv. //vesicatoria// contains multiple export signals and can enter plant cells in the absence of the type III secretion translocon. Front Microbiol. 8: 2180. DOI: [[https://doi.org/10.3389/fmicb.2017.02180|10.3389/fmicb.2017.02180]]
 Stella S, Molina R, Yefimenko I, Prieto J, Silva G, Bertonati C, Juillerat A, Duchateau P, Montoya G (2013). Structure of the AvrBs3–DNA complex provides new insights into the initial thymine-recognition mechanism. Acta Cryst. 69: 1707-1716. DOI: [[http://dx.doi.org/10.1107/S0907444913016429|10.1107/S0907444913016429]]
@@ Line 128: / Line 124: @@
 Hutin M, Pérez-Quintero AL, Lopez C, Szurek B (2015). MorTAL Kombat: the story of defense against TAL effectors through loss-of-susceptibility. Front. Plant Sci. 6: 535. DOI: [[https://doi.org/10.3389/fpls.2015.00535|10.3389/fpls.2015.00535]]. Erratum in: Front Plant Sci. (2015) 6: 647.
-Scholze H, Boch J (2010). TAL effector-DNA specificity. Virulence 1: 428-432. DOI: [[https://doi.org/10.4161/viru.1.5.12863|10.4161/viru.1.5.12863]]
+Xue J, Lu Z, Liu W, Wang S, Lu D, Wang X, He X (2020). The genetic arms race between plant and //Xanthomonas//: lessons learned from TALE biology. Sci. China Life Sci. 63. DOI: [[https://doi.org/10.1007/s11427-020-1699-4|10.1007/s11427-020-1699-4]]
-Scholze H, Boch J (2011). TAL effectors are remote controls for gene activation. Curr. Opin. Microbiol. 14: 47-53. DOI: [[https://doi.org/10.1016/j.mib.2010.12.001|10.1016/j.mib.2010.12.001]]
-Yuan M, Ke Y, Huang R, Ma L, Yang Z, Chu Z, Xiao J, Li X, Wang S (2016). A host basal transcription factor is a key component for infection of rice by TALE-carrying bacteria. Elife 5: DOI: [[https://doi.org/10.7554/eLife.19605|10.7554/eLife.19605]]
 Zhang J, Yin Z, White F (2015). TAL effectors and the executor //R// genes. Front. Plant Sci. 6: 641. DOI: [[https://doi.org/10.3389/fpls.2015.00641|10.3389/fpls.2015.00641]]

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