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Streptomyces scabies, a causal agent of potato common scab, has the ability to degrade aromatic constituents of tuber periderm

Carole Beaulieu: Université de Sherbrooke

<div><span>The potato periderm contains layers of suberized cells. Suberin is composed of an aliphatic domain covalently linked to an aromatic domain. <em>S. scabies</em> has the ability to degrade the aliphatic domain but degradation of the aromatic domain has not been documented. The last domain is composed of cinnamic acids such as ferulic and coumaric acids. These compounds were added to <em>S. scabies</em> culture medium and it was shown that the pathogen efficiently utilized these aromatics. In contrast, other common scab-inducing species exhibited a poor utilization capacity. <em>S. scabies</em> thus appears to be more adapted to its host than the new emerging pathogens. A bioinformatics study suggests that ferulic and coumaric acids catabolism occurred via the β-ketoadipate pathway. The gene SCAB_15301 encoding a vanillate monooxygenase was deleted from <em>S. scabies </em>genome. The mutant retained its ability to catabolize ferulic acid into vanillate but could not further degrade the latter compound. While ferulic acid induced in the wild strain the expression of genes associated with the β-ketoadipate pathway, no gene expression was recorded in the mutant. When grown in the presence of suberin-enriched potato periderm, accumulation of vanillic acid was observed only for the mutant. This work thus brought evidence that <em>S. scabies</em> could degrade not only the aliphatic part of suberin but also constituents of the aromatic domain. Suberin degradation may facilitate colonization as well as tuber infection.</span></div>