The txtAB genes of the plant pathogen Streptomyces acidiscabies encode a peptide synthetase required for phytotoxin thaxtomin A production and pathogenicity. Healy, F., G., Wach, M., Krasnoff, S., B., Gibson, D., M., & Loria, R. Molecular Microbiology, 38(4):794-804, 2000.
abstract   bibtex   
Four Streptomyces species have been described as the causal agents of scab disease, which affects economically important root and tuber crops worldwide. These species produce a family of cyclic dipeptides, the thaxtomins, which alone mimic disease symptomatology. Structural considerations suggest that thaxtomins are synthesized non-ribosomally. Degenerate oligonucleotide primers were used to amplify conserved portions of the acyladenylation module of peptide synthetase genes from genomic DNA of representatives of the four species. Pairwise Southern hybridizations identified a peptide synthetase acyladenylation module conserved among three species. The complete nucleotide sequences of two peptide synthetase genes (txtAB) were determined from S. acidiscabies 84.104 cosmid library clones. The organization of the deduced TxtA and TxtB peptide synthetase catalytic domains is consistent with the formation of N-methylated cyclic dipeptides such as thaxtomins. Based on high-performance liquid chromatography (HPLC) analysis, thaxtomin A production was abolished in txtA gene disruption mutants. Although the growth and morphological characteristics of the mutants were identical to those of the parent strain, txtA mutants were avirulent on potato tubers. Moreover, introduction of the thaxtomin synthetase cosmid into a txtA mutant restored both pathogenicity and thaxtomin A production, demonstrating a critical role for thaxtomins in pathogenesis.
@article{
 title = {The txtAB genes of the plant pathogen Streptomyces acidiscabies encode a peptide synthetase required for phytotoxin thaxtomin A production and pathogenicity},
 type = {article},
 year = {2000},
 keywords = {Bacterial Proteins,Gene Expression Regulation, Bacterial,Indoles,Molecular Sequence Data,Peptide Synthases,Piperazines,Plants,Southern blotting,Streptomyces,Streptomyces acidiscabies,Support, U.S. Gov't, Non-P.H.S.,Virulence,adenylation,agriculture,article,bacterial genetics,controlled study,dipeptide,genetic analysis,high performance liquid chromatography,nonhuman,nucleotide sequence,oligonucleotide,pathogenicity,peptide synthase,plant toxin,potato,priority journal,protein analysis,ribosome,sequence analysis,structure activity relation,structure analysis,thaxtomin A,toxin structure,toxin synthesis,unclassified drug},
 pages = {794-804},
 volume = {38},
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 abstract = {Four Streptomyces species have been described as the causal agents of scab disease, which affects economically important root and tuber crops worldwide. These species produce a family of cyclic dipeptides, the thaxtomins, which alone mimic disease symptomatology. Structural considerations suggest that thaxtomins are synthesized non-ribosomally. Degenerate oligonucleotide primers were used to amplify conserved portions of the acyladenylation module of peptide synthetase genes from genomic DNA of representatives of the four species. Pairwise Southern hybridizations identified a peptide synthetase acyladenylation module conserved among three species. The complete nucleotide sequences of two peptide synthetase genes (txtAB) were determined from S. acidiscabies 84.104 cosmid library clones. The organization of the deduced TxtA and TxtB peptide synthetase catalytic domains is consistent with the formation of N-methylated cyclic dipeptides such as thaxtomins. Based on high-performance liquid chromatography (HPLC) analysis, thaxtomin A production was abolished in txtA gene disruption mutants. Although the growth and morphological characteristics of the mutants were identical to those of the parent strain, txtA mutants were avirulent on potato tubers. Moreover, introduction of the thaxtomin synthetase cosmid into a txtA mutant restored both pathogenicity and thaxtomin A production, demonstrating a critical role for thaxtomins in pathogenesis.},
 bibtype = {article},
 author = {Healy, F G and Wach, M and Krasnoff, S B and Gibson, D M and Loria, R},
 journal = {Molecular Microbiology},
 number = {4}
}

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