Cloning and characterization of the thaxtomin C biosynthetic gene cluster of the bacterial sweet potato pathogen Streptomyces ipomoeae

Certain members of the bacterial genus Streptomyces are pathogens which attack roots and other underground structures of plants. Phytotoxins known as thaxtomins are essential virulence factors of these bacteria and appear to target the plant cell wall. Streptomyces potato pathogens synthesize thaxto...

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Bibliographic Details
Published in:Phytopathology 2006-06, Vol.96 (6), p.S42-S42
Main Authors: Grau, B L, Guan, D, Loria, R, Pettis, G S
Format: Article
Language:English
Subjects:
Bacteria
Solanum tuberosum
Streptomyces
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Summary:Certain members of the bacterial genus Streptomyces are pathogens which attack roots and other underground structures of plants. Phytotoxins known as thaxtomins are essential virulence factors of these bacteria and appear to target the plant cell wall. Streptomyces potato pathogens synthesize thaxtomin A predominantly while the sweet potato pathogen Streptomyces ipomoeae produces mainly the less-modified thaxtomin C. The thaxtomin A biosynthetic gene cluster in Streptomyces turgidiscabies consists of several essential genes including txtA and txtB, which encode a thaxtomin A peptide synthetase, txtC, which specifies a P-450 monooxygenase, and nos, which encodes nitric oxide synthase. To begin characterization of the thaxtomin C genes of S. ipomoeae, a probe specific for the S. turgidiscabies nos gene was used in colony blot hybridizations to identify positive clones within a S. ipomoeae cosmid library. One cosmid, pSIP19, was found to contain what may be the entire thaxtomin C gene cluster. Homologs of txtA, txtB, and nos genes were organized similarly to those in S. turgidiscabies. No evidence of a txtC homolog in its characteristic position downstream of txtB was found on pSIP19, which may indicate that such a gene is not required for thaxtomin C synthesis.
ISSN:0031-949X