Streptomyces scabies 87-22 possesses a functional tomatinase.
The actinomycete Streptomyces scabies 87-22 is the causal agent of common scab, an economically important disease of potato and taproot crops. Sequencing of the S. scabies 87-22 genome revealed the presence of a gene with high homology to the gene encoding the alpha-tomatine-detoxifying enzyme tomatinase found in fungal tomato pathogens. The tomA gene from S. scabies 87-22 was cotranscribed with a putative family 1 glycosyl hydrolase gene, and purified TomA protein was active only on alpha-tomatine and not potato glycoalkaloids or xylans. Tomatinase-null mutants were more sensitive to alpha-tomatine than the wild-type strain in a disk diffusion assay. Interestingly, tomatine affected only aerial mycelium and not vegetative mycelium, suggesting that the target(s) of alpha-tomatine is not present during vegetative growth. Severities of disease for tomato seedlings affected by S. scabies 87-22 wild-type and DeltatomA1 strains were indistinguishable, suggesting that tomatinase is not important in pathogenicity on tomato plants. However, conservation of tomA on a pathogenicity island in S. acidiscabies and S. turgidiscabies suggests a role in plant-microbe interaction.
Seipke
Ryan F
RF
Department of Plant Pathology, Cornell University, 334 Plant Science Building, Ithaca, NY 14853, USA.
Loria
Rosemary
R
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D006026:Glycoside Hydrolases / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D013302:Streptomyces / Q000201:enzymology*; D014053:Tomatine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism
D001426:Bacterial Proteins; C003677:tomatidine; D014053:Tomatine; D006026:Glycoside Hydrolases; C099475:tomatinase