Limits...
Genes Involved in the Production of Antimetabolite Toxins by Pseudomonas syringae Pathovars.

Arrebola E, Cazorla FM, Pérez-García A, Vicente Ad - Genes (Basel) (2011)

Bottom Line: The antimetabolite toxins are generally located in gene clusters present in the flexible genomes of specific strains.These gene clusters are typically present in blocks of genes that appear to be integrated into specific sites in the P. syringae core genome.A general overview of the genetic organization and biosynthetic and regulatory functions of these genetic traits of the antimetabolite toxins will be given in the present work.

View Article: PubMed Central - PubMed

Affiliation: Experimental Station La Mayora, Institute of Subtropical Horticulture and Mediterranean "La Mayora" (IHSM-UMA-CSIC), Algarrobo-Costa (Málaga) 29750, Spain. arrebolad@eelm.csic.es.

ABSTRACT
Pseudomonas syringae is pathogenic in a wide variety of plants, causing diseases with economic impacts. Pseudomonas syringae pathovars produce several toxins that can function as virulence factors and contribute to disease symptoms. These virulence factors include antimetabolite toxins, such as tabtoxin, phaseolotoxin and mangotoxin, which target enzymes in the pathways of amino acid metabolism. The antimetabolite toxins are generally located in gene clusters present in the flexible genomes of specific strains. These gene clusters are typically present in blocks of genes that appear to be integrated into specific sites in the P. syringae core genome. A general overview of the genetic organization and biosynthetic and regulatory functions of these genetic traits of the antimetabolite toxins will be given in the present work.

No MeSH data available.


Related in: MedlinePlus

Structural organization of the mangotoxin gene cluster in the genomic clone pCG2-6. The different CDs are represented by arrows indicating the direction of transcription. The grey arrows indicate the mgo operon (black band) genes. Other genes identified by researchers are also shown in the figure. Figure partially adapted from Arrebola et al. [62].
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3927611&req=5

f6-genes-02-00640: Structural organization of the mangotoxin gene cluster in the genomic clone pCG2-6. The different CDs are represented by arrows indicating the direction of transcription. The grey arrows indicate the mgo operon (black band) genes. Other genes identified by researchers are also shown in the figure. Figure partially adapted from Arrebola et al. [62].

Mentions: Other genes involved in mangotoxin production have been detected (Figure 6, Table 3), including mgoA [62]. The mgoA gene showed high similarity to non-ribosomal peptide synthetase (NRPS), an enzymatic system involved in the synthesis of antibiotic peptides via the non-ribosomal thiotemplate mechanism of biosynthesis. Analysis of the predicted amino acid sequence from mgoA indicates that it contains only one amino acid activation module typical of a functional NRPS. It contains the typical aminoacyl adenylation domain, found at the N-terminal end, which seems to be responsible for recognizing and adenylating of the carboxylic acid of the amino acid substrate [64]. A condensation domain is conventionally fused to the amino-terminal end of modules accepting acyl groups from the preceding module [65]. Three potential reductase domains were also identified at the carboxyl-terminal end of MgoA [62]. The gene mgoA is surrounded by several genes (Figure 6, Table 3), whose functions are still unknown. The genes mgoB, mgoC and mgoD, corresponding to the ORFs 3, 4 and 6, allow a hypothetical protein group, whose putative function is very difficult to establish because it does not have a clear functional domain. However, a very recent study undertaken to characterize the transcriptional organization of the mgo gene cluster has determined the possible functions of mgoB, mgoC and mgoD [66]. In this study, Arrebola et al. [66] propose that both mgoB and mgoC could be oxygenases. Specifically, mgoB's product is similar to the Haem oxygenase-like, multi-helical superfamily, and mgoC bears significant similarity to the p-aminobenzoate N-oxygenase of Streptomyces thioluteus. In contrast, mgoD is similar to two possible domains, a polyketide cyclase and a lipid transporter domain. These four genes, mgoBCAD, are co-transcribed in only one transcript, the absence of which produces mangotoxin-defective mutants. Upstream of mgoB is located a functional promoter, where oligonucleotides related to a known transcription factors rpoD (σ70) binding site are present. A functional terminator has been located downstream of mgoD as well, characterizing the complete mgo operon [66]. This operon is highly homologous to the pvf gene cluster identified in P. entomophila, a bacterium that is lethal to Drosophila melanogaster [67]. Vallet-Gely et al. [67] have proposed that the pvf gene cluster of P. entomophila could perform a regulatory role involved in the production of virulence factors in Pseudomonas species [67]. Based on studies conducted by Vallet-Gely et al., a possible regulatory role for the mgo operon could also be proposed. Performing the same experiment described by Vallet-Gely et al., Arrebola et al. observed a complementation when extract from wild type UMAF0158 was used in cultures containing mutants for the gac and mgo operons, which led them to suggest a possible regulatory role for the mgo operon similar to that proposed by Vallet-Gely et al. for the pvf genes [66].


Genes Involved in the Production of Antimetabolite Toxins by Pseudomonas syringae Pathovars.

Arrebola E, Cazorla FM, Pérez-García A, Vicente Ad - Genes (Basel) (2011)

Structural organization of the mangotoxin gene cluster in the genomic clone pCG2-6. The different CDs are represented by arrows indicating the direction of transcription. The grey arrows indicate the mgo operon (black band) genes. Other genes identified by researchers are also shown in the figure. Figure partially adapted from Arrebola et al. [62].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927611&req=5

f6-genes-02-00640: Structural organization of the mangotoxin gene cluster in the genomic clone pCG2-6. The different CDs are represented by arrows indicating the direction of transcription. The grey arrows indicate the mgo operon (black band) genes. Other genes identified by researchers are also shown in the figure. Figure partially adapted from Arrebola et al. [62].
Mentions: Other genes involved in mangotoxin production have been detected (Figure 6, Table 3), including mgoA [62]. The mgoA gene showed high similarity to non-ribosomal peptide synthetase (NRPS), an enzymatic system involved in the synthesis of antibiotic peptides via the non-ribosomal thiotemplate mechanism of biosynthesis. Analysis of the predicted amino acid sequence from mgoA indicates that it contains only one amino acid activation module typical of a functional NRPS. It contains the typical aminoacyl adenylation domain, found at the N-terminal end, which seems to be responsible for recognizing and adenylating of the carboxylic acid of the amino acid substrate [64]. A condensation domain is conventionally fused to the amino-terminal end of modules accepting acyl groups from the preceding module [65]. Three potential reductase domains were also identified at the carboxyl-terminal end of MgoA [62]. The gene mgoA is surrounded by several genes (Figure 6, Table 3), whose functions are still unknown. The genes mgoB, mgoC and mgoD, corresponding to the ORFs 3, 4 and 6, allow a hypothetical protein group, whose putative function is very difficult to establish because it does not have a clear functional domain. However, a very recent study undertaken to characterize the transcriptional organization of the mgo gene cluster has determined the possible functions of mgoB, mgoC and mgoD [66]. In this study, Arrebola et al. [66] propose that both mgoB and mgoC could be oxygenases. Specifically, mgoB's product is similar to the Haem oxygenase-like, multi-helical superfamily, and mgoC bears significant similarity to the p-aminobenzoate N-oxygenase of Streptomyces thioluteus. In contrast, mgoD is similar to two possible domains, a polyketide cyclase and a lipid transporter domain. These four genes, mgoBCAD, are co-transcribed in only one transcript, the absence of which produces mangotoxin-defective mutants. Upstream of mgoB is located a functional promoter, where oligonucleotides related to a known transcription factors rpoD (σ70) binding site are present. A functional terminator has been located downstream of mgoD as well, characterizing the complete mgo operon [66]. This operon is highly homologous to the pvf gene cluster identified in P. entomophila, a bacterium that is lethal to Drosophila melanogaster [67]. Vallet-Gely et al. [67] have proposed that the pvf gene cluster of P. entomophila could perform a regulatory role involved in the production of virulence factors in Pseudomonas species [67]. Based on studies conducted by Vallet-Gely et al., a possible regulatory role for the mgo operon could also be proposed. Performing the same experiment described by Vallet-Gely et al., Arrebola et al. observed a complementation when extract from wild type UMAF0158 was used in cultures containing mutants for the gac and mgo operons, which led them to suggest a possible regulatory role for the mgo operon similar to that proposed by Vallet-Gely et al. for the pvf genes [66].

Bottom Line: The antimetabolite toxins are generally located in gene clusters present in the flexible genomes of specific strains.These gene clusters are typically present in blocks of genes that appear to be integrated into specific sites in the P. syringae core genome.A general overview of the genetic organization and biosynthetic and regulatory functions of these genetic traits of the antimetabolite toxins will be given in the present work.

View Article: PubMed Central - PubMed

Affiliation: Experimental Station La Mayora, Institute of Subtropical Horticulture and Mediterranean "La Mayora" (IHSM-UMA-CSIC), Algarrobo-Costa (Málaga) 29750, Spain. arrebolad@eelm.csic.es.

ABSTRACT
Pseudomonas syringae is pathogenic in a wide variety of plants, causing diseases with economic impacts. Pseudomonas syringae pathovars produce several toxins that can function as virulence factors and contribute to disease symptoms. These virulence factors include antimetabolite toxins, such as tabtoxin, phaseolotoxin and mangotoxin, which target enzymes in the pathways of amino acid metabolism. The antimetabolite toxins are generally located in gene clusters present in the flexible genomes of specific strains. These gene clusters are typically present in blocks of genes that appear to be integrated into specific sites in the P. syringae core genome. A general overview of the genetic organization and biosynthetic and regulatory functions of these genetic traits of the antimetabolite toxins will be given in the present work.

No MeSH data available.


Related in: MedlinePlus