Streptomyces scabies 87-22 possesses a functional tomatinase

Area of Science:

• Microbiology
• Plant Pathology
• Biochemistry

Background:

• Streptomyces scabies 87-22 causes common scab, a significant disease in potato and taproot crops.
• Genomic analysis of S. scabies 87-22 revealed a gene homologous to alpha-tomatine-detoxifying enzyme tomatinase.

Purpose of the Study:

• To investigate the function and significance of the tomA gene in Streptomyces scabies 87-22.
• To determine the role of tomatinase in alpha-tomatine detoxification and pathogenicity.

Main Methods:

• Gene sequencing and homology analysis.
• Protein purification and enzymatic activity assays.
• Construction and testing of tomatinase-null mutants.
• Disk diffusion assays to assess sensitivity to alpha-tomatine.
• Pathogenicity tests on tomato seedlings.

Main Results:

• The tomA gene was cotranscribed with a glycosyl hydrolase gene.
• Purified TomA protein specifically detoxified alpha-tomatine, with no activity against potato glycoalkaloids or xylans.
• Tomatinase-null mutants showed increased sensitivity to alpha-tomatine, affecting aerial but not vegetative mycelium.
• Tomatinase was not essential for S. scabies pathogenicity on tomato plants.

Conclusions:

• The tomatinase enzyme in S. scabies 87-22 detoxifies alpha-tomatine, primarily affecting aerial mycelium.
• While not critical for tomato pathogenicity, the conserved tomA gene suggests a role in plant-microbe interactions.