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TAL effectors and the executor R genes.

Zhang J, Yin Z, White F - Front Plant Sci (2015)

Bottom Line: Transcription activator-like (TAL) effectors are bacterial type III secretion proteins that function as transcription factors in plants during Xanthomonas/plant interactions, conditioning either host susceptibility and/or host resistance.Three types of TAL effector associated resistance (R) genes have been characterized-recessive, dominant non-transcriptional, and dominant TAL effector-dependent transcriptional based resistance.Here, we discuss the last type of R genes, whose functions are dependent on direct TAL effector binding to discrete effector binding elements in the promoters.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Pathology, Kansas State University , Manhattan, KS, USA.

ABSTRACT
Transcription activator-like (TAL) effectors are bacterial type III secretion proteins that function as transcription factors in plants during Xanthomonas/plant interactions, conditioning either host susceptibility and/or host resistance. Three types of TAL effector associated resistance (R) genes have been characterized-recessive, dominant non-transcriptional, and dominant TAL effector-dependent transcriptional based resistance. Here, we discuss the last type of R genes, whose functions are dependent on direct TAL effector binding to discrete effector binding elements in the promoters. Only five of the so-called executor R genes have been cloned, and commonalities are not clear. We have placed the protein products in two groups for conceptual purposes. Group 1 consists solely of the protein from pepper, BS3, which is predicted to have catalytic function on the basis of homology to a large conserved protein family. Group 2 consists of BS4C-R, XA27, XA10, and XA23, all of which are relatively short proteins from pepper or rice with multiple potential transmembrane domains. Group 2 members have low sequence similarity to proteins of unknown function in closely related species. Firm predictions await further experimentation on these interesting new members to the R gene repertoire, which have potential broad application in new strategies for disease resistance.

No MeSH data available.


Related in: MedlinePlus

The known E proteins. (A) A phylogenetic tree of BS3 related proteins. Proteins from closely related YUCCA proteins of C. annuum L. (Ca), A. thaliana (At), Tomato (To), Citrus sinensis (Cs) and the BS3 protein (Capana02g001306) were aligned. Names of proteins are given with the Phytozome ID or Pepper Genome Database ID (in parentheses). A monophyletic group that contains the predicted BS3 protein and tomato YUCCA-like proteins is boxed in red. Sequences were aligned with the online ClustalW server (http://www.ch.embnet.org/software/ClustalW.html) using the default values. MEGA6.0 was used for generating a tree on the basis of ClustalW output. Phylogenetic calculations are based on the maximum likelihood method, and Bootstrap analysis was used to evaluate the reliability of the nodes of the phylogenetic trees. Bootstrap values are based on 1000 replications. The branch lengths of the tree are proportional to divergence. The 0.1 scale represents 10% change. (B) Structural predictions for group 2 E proteins. (i) Bs4C-R; (ii) XA27; (iii) XA10 and XA23. Alignment of XA10 and XA23 was conducted using the online program ClustalW2 using the default parameters (http://www.ebi.ac.uk/Tools/msa/clustalw2/). Transmembrane helices predicted by the SOSUI program (http://bp.nuap.nagoya-u.ac.jp/sosui/sosui_submit.html) are highlighted in yellow. * Represents no amino acid residue at what would otherwise be position 13.
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Figure 2: The known E proteins. (A) A phylogenetic tree of BS3 related proteins. Proteins from closely related YUCCA proteins of C. annuum L. (Ca), A. thaliana (At), Tomato (To), Citrus sinensis (Cs) and the BS3 protein (Capana02g001306) were aligned. Names of proteins are given with the Phytozome ID or Pepper Genome Database ID (in parentheses). A monophyletic group that contains the predicted BS3 protein and tomato YUCCA-like proteins is boxed in red. Sequences were aligned with the online ClustalW server (http://www.ch.embnet.org/software/ClustalW.html) using the default values. MEGA6.0 was used for generating a tree on the basis of ClustalW output. Phylogenetic calculations are based on the maximum likelihood method, and Bootstrap analysis was used to evaluate the reliability of the nodes of the phylogenetic trees. Bootstrap values are based on 1000 replications. The branch lengths of the tree are proportional to divergence. The 0.1 scale represents 10% change. (B) Structural predictions for group 2 E proteins. (i) Bs4C-R; (ii) XA27; (iii) XA10 and XA23. Alignment of XA10 and XA23 was conducted using the online program ClustalW2 using the default parameters (http://www.ebi.ac.uk/Tools/msa/clustalw2/). Transmembrane helices predicted by the SOSUI program (http://bp.nuap.nagoya-u.ac.jp/sosui/sosui_submit.html) are highlighted in yellow. * Represents no amino acid residue at what would otherwise be position 13.

Mentions: E proteins are not related on the basis of sequence to any other type of R protein. In fact, the proteins, with the exception of the recently reported XA10 and XA23, share no sequence identity with each other. Conceptually, the E genes and their products can be divided into two groups. Group 1 consists of proteins that likely have a function in plant development or physiology and whose function has been hijacked by host adaptation to disease. Group 1 consists solely of BS3, which is a member of a conserved family of proteins known as flavin mono-oxygenases (FMO) and, more specifically, a subclass of FMOs known variously as YUCCA or FLOOZY (Figure 2A; Römer et al., 2007; Exposito-Rodriguez et al., 2011; Zhao, 2014). Group 2 members, of which there are four, are relatively short proteins that have multiple hydrophobic potential membrane spanning domains (Figure 2B). The proteins share no sequence relatedness with proteins of known function and the relatively few related coding sequences occur within close relatives. One related sequence outside the Solanaceae, from grapevine, was reported for Bs3C-R. Several of the E proteins may have structural similarities. XA27 and XA10 are predicted or have been shown to localize to host cellular membranes and XA10, more specifically, has been shown to localize to the endoplasmic reticulum (ER; Wu et al., 2008; Tian et al., 2014). Prediction software also indicates that BS4C-R may be localized to the ER (Nakai and Horton, 1999; Strauss et al., 2012). It is tempting to speculate that BS3 requires catalytic activity for the R gene response and the group 2 proteins function as R proteins due to their interaction with host organelles. However, whether the predicted catalytic functions of BS3 are required for the R gene response has not been reported, and future analysis of the mechanism-of-action for the respective proteins may indicate some common feature.


TAL effectors and the executor R genes.

Zhang J, Yin Z, White F - Front Plant Sci (2015)

The known E proteins. (A) A phylogenetic tree of BS3 related proteins. Proteins from closely related YUCCA proteins of C. annuum L. (Ca), A. thaliana (At), Tomato (To), Citrus sinensis (Cs) and the BS3 protein (Capana02g001306) were aligned. Names of proteins are given with the Phytozome ID or Pepper Genome Database ID (in parentheses). A monophyletic group that contains the predicted BS3 protein and tomato YUCCA-like proteins is boxed in red. Sequences were aligned with the online ClustalW server (http://www.ch.embnet.org/software/ClustalW.html) using the default values. MEGA6.0 was used for generating a tree on the basis of ClustalW output. Phylogenetic calculations are based on the maximum likelihood method, and Bootstrap analysis was used to evaluate the reliability of the nodes of the phylogenetic trees. Bootstrap values are based on 1000 replications. The branch lengths of the tree are proportional to divergence. The 0.1 scale represents 10% change. (B) Structural predictions for group 2 E proteins. (i) Bs4C-R; (ii) XA27; (iii) XA10 and XA23. Alignment of XA10 and XA23 was conducted using the online program ClustalW2 using the default parameters (http://www.ebi.ac.uk/Tools/msa/clustalw2/). Transmembrane helices predicted by the SOSUI program (http://bp.nuap.nagoya-u.ac.jp/sosui/sosui_submit.html) are highlighted in yellow. * Represents no amino acid residue at what would otherwise be position 13.
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Figure 2: The known E proteins. (A) A phylogenetic tree of BS3 related proteins. Proteins from closely related YUCCA proteins of C. annuum L. (Ca), A. thaliana (At), Tomato (To), Citrus sinensis (Cs) and the BS3 protein (Capana02g001306) were aligned. Names of proteins are given with the Phytozome ID or Pepper Genome Database ID (in parentheses). A monophyletic group that contains the predicted BS3 protein and tomato YUCCA-like proteins is boxed in red. Sequences were aligned with the online ClustalW server (http://www.ch.embnet.org/software/ClustalW.html) using the default values. MEGA6.0 was used for generating a tree on the basis of ClustalW output. Phylogenetic calculations are based on the maximum likelihood method, and Bootstrap analysis was used to evaluate the reliability of the nodes of the phylogenetic trees. Bootstrap values are based on 1000 replications. The branch lengths of the tree are proportional to divergence. The 0.1 scale represents 10% change. (B) Structural predictions for group 2 E proteins. (i) Bs4C-R; (ii) XA27; (iii) XA10 and XA23. Alignment of XA10 and XA23 was conducted using the online program ClustalW2 using the default parameters (http://www.ebi.ac.uk/Tools/msa/clustalw2/). Transmembrane helices predicted by the SOSUI program (http://bp.nuap.nagoya-u.ac.jp/sosui/sosui_submit.html) are highlighted in yellow. * Represents no amino acid residue at what would otherwise be position 13.
Mentions: E proteins are not related on the basis of sequence to any other type of R protein. In fact, the proteins, with the exception of the recently reported XA10 and XA23, share no sequence identity with each other. Conceptually, the E genes and their products can be divided into two groups. Group 1 consists of proteins that likely have a function in plant development or physiology and whose function has been hijacked by host adaptation to disease. Group 1 consists solely of BS3, which is a member of a conserved family of proteins known as flavin mono-oxygenases (FMO) and, more specifically, a subclass of FMOs known variously as YUCCA or FLOOZY (Figure 2A; Römer et al., 2007; Exposito-Rodriguez et al., 2011; Zhao, 2014). Group 2 members, of which there are four, are relatively short proteins that have multiple hydrophobic potential membrane spanning domains (Figure 2B). The proteins share no sequence relatedness with proteins of known function and the relatively few related coding sequences occur within close relatives. One related sequence outside the Solanaceae, from grapevine, was reported for Bs3C-R. Several of the E proteins may have structural similarities. XA27 and XA10 are predicted or have been shown to localize to host cellular membranes and XA10, more specifically, has been shown to localize to the endoplasmic reticulum (ER; Wu et al., 2008; Tian et al., 2014). Prediction software also indicates that BS4C-R may be localized to the ER (Nakai and Horton, 1999; Strauss et al., 2012). It is tempting to speculate that BS3 requires catalytic activity for the R gene response and the group 2 proteins function as R proteins due to their interaction with host organelles. However, whether the predicted catalytic functions of BS3 are required for the R gene response has not been reported, and future analysis of the mechanism-of-action for the respective proteins may indicate some common feature.

Bottom Line: Transcription activator-like (TAL) effectors are bacterial type III secretion proteins that function as transcription factors in plants during Xanthomonas/plant interactions, conditioning either host susceptibility and/or host resistance.Three types of TAL effector associated resistance (R) genes have been characterized-recessive, dominant non-transcriptional, and dominant TAL effector-dependent transcriptional based resistance.Here, we discuss the last type of R genes, whose functions are dependent on direct TAL effector binding to discrete effector binding elements in the promoters.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Pathology, Kansas State University , Manhattan, KS, USA.

ABSTRACT
Transcription activator-like (TAL) effectors are bacterial type III secretion proteins that function as transcription factors in plants during Xanthomonas/plant interactions, conditioning either host susceptibility and/or host resistance. Three types of TAL effector associated resistance (R) genes have been characterized-recessive, dominant non-transcriptional, and dominant TAL effector-dependent transcriptional based resistance. Here, we discuss the last type of R genes, whose functions are dependent on direct TAL effector binding to discrete effector binding elements in the promoters. Only five of the so-called executor R genes have been cloned, and commonalities are not clear. We have placed the protein products in two groups for conceptual purposes. Group 1 consists solely of the protein from pepper, BS3, which is predicted to have catalytic function on the basis of homology to a large conserved protein family. Group 2 consists of BS4C-R, XA27, XA10, and XA23, all of which are relatively short proteins from pepper or rice with multiple potential transmembrane domains. Group 2 members have low sequence similarity to proteins of unknown function in closely related species. Firm predictions await further experimentation on these interesting new members to the R gene repertoire, which have potential broad application in new strategies for disease resistance.

No MeSH data available.


Related in: MedlinePlus