Isolation and structural characterization of a non-diketopiperazine phytotoxin from a potato pathogenic Streptomyces strain

Abstract

Two Streptomyces spp. strains responsible for potato common scab infections in Uruguay which do not produce diketopiperazines were identified through whole-genome sequencing, and the virulence factor produced by one of them was isolated and characterized. Phylogenetic analysis showed that both pathogenic strains can be identified as S. niveiscabiei, and the structure of the phytotoxin was elucidated as that of the polyketide desmethylmensacarcin using MS and NMR methods. The metabolite is produced in yields of ∼200 mg/L of culture media, induces deep necrotic lesions on potato tubers, stuns root and shoot growth in radish seedlings, and is comparatively more aggressive than thaxtomin A. This is the first time that desmethylmensacarcin, a member of a class of compounds known for their antitumor and antibiotic activity, is associated with phytotoxicity. More importantly, it represents the discovery of a new virulence factor related to potato common scab, an economically-important disease affecting potato production worldwide.

Graphical Abstract

Keywords:

• Desmethylmensacarcin
• phytotoxin
• potato common scab
• Streptomyces spp

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Funding from the Comisión Sectorial de Investigación Científica (awards IIM2 81/2015 and I + D 166/2016), the Comisión Académica de Posgrado, and the Programa de Desarrollo de las Ciencias Básicas is acknowledged. We also wish to thank Marcos Colazzo for recording the ESIMS² spectra, and Horacio Heinzen and Guillermo Valdomir for their assistance in procuring the HRESIMS data.