title: Inhibitory Effects of Macrotetrolides fromStreptomycesspp. On Zoosporogenesis and Motility of Peronosporomycete Zoospores Are Likely Linked with Enhanced ATPase Activity in Mitochondria.
abstract: The release of zoospores from sporangia and motility of the released zoospores are critical in the disease cycle of the Peronosporomycetes that cause devastating diseases in plants, fishes, animals and humans. Disruption of any of these asexual life stages eliminates the possibility of pathogenesis. In the course of screening novel bioactive secondary metabolites, we found that extracts of some strains of marineStreptomycesspp. rapidly impaired motility and caused subsequent lysis of zoospores of the grapevine downy mildew pathogenPlasmopara viticolaat 10 μg/ml. We tested a number of secondary metabolites previously isolated from these strains and found that macrotetrolide antibiotics such as nonactin, monactin, dinactin and trinactin, and nactic acids such as (+)-nonactic acid, (+)-homonactic acid, nonactic acid methyl ester, homonactic acid methyl ester, bonactin and feigrisolide C impaired motility and caused subsequent lysis ofP. viticolazoospores in a dose- and time-dependent manners with dinactin being the most active compound (MIC 0.3 μg/ml). A cation channel-forming compound, gramicidin, and a carrier of monovalent cations, nigericin also showed similar biological activities. Among all 12 compounds tested, gramicidin most potently arrested the motility of zoospores at concentrations starting from 0.1 μg/ml. All macrotetrolide antibiotics also displayed similar motility impairing activities againstP. viticola, Phytophthora capsici, andAphanomyces cochlioideszoospores indicating non-specific biological effects of these compounds toward peronosporomyctes. Furthermore, macrotetrolide antibiotics and gramicidin also markedly suppressed the release of zoospores from sporangia ofP. viticolain a dose-dependent manner. As macrotetrolide antibiotics and gramicidin are known as enhancers of mitochondrial ATPase activity, inhibition of zoosporogenesis and motility of zoospores by these compounds are likely linked with hydrolysis of ATP through enhanced ATPase activity in mitochondria. This is the first report on motility inhibitory and lytic activities of macrotetrolide antibiotics and nactic acids against the zoospores of peronosporomycete phytopathogens.
authors.affiliation: Division of Plant Pathology and Plant Protection, Department of Crop Sciences, Georg-August-Universität GöttingenGöttingen, Germany; Department of Biotechnology, Bangabandhu Sheikh Mujibur Rahman Agricultural UniversityGazipur, Bangladesh.
authors.forename: Md Tofazzal
authors.initials: MT
authors.lastname: Islam
authors.affiliation: Institute of Organic and Biomolecular Chemistry, Georg-August-Universität Göttingen Göttingen, Germany.
authors.forename: Hartmut
authors.initials: H
authors.lastname: Laatsch
authors.affiliation: Department of Biotechnology, Bangabandhu Sheikh Mujibur Rahman Agricultural University Gazipur, Bangladesh.
authors.forename: Andreas
authors.initials: A
authors.lastname: von Tiedemann
keywords: biological control; dinactin; ionophore; mitochondrial ATPase activity; zoosporocides