Khatmiamycin, a motility inhibitor and zoosporicide against the grapevine downy mildew pathogen Plasmopara viticola from Streptomyces sp. ANK313
Khatmiamycin, a motility inhibitor and zoosporicide against the grapevine downy mildew pathogen Plasmopara viticola from Streptomyces sp. ANK313
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Date
2011-08
Authors
Muna Ali
Journal Title
Journal ISSN
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Publisher
University of Khartoum
Abstract
Peronosporomycetes are distinct from fungi and are phylogenetic
relatives of brown algae and diatoms. They cause many destructive
diseases in plants, animals, fishes and humans.1,2 One of the most
notorious members of peronosporomycetes, Plasmopara viticola, is an
obligate biotroph and a serious pathogen of grapevine worldwide.
Many fungicides are ineffective against this phytopathogen, and hence,
bioactive compounds with new modes of action are needed to combat
this economically important pest. Under favorable environmental
conditions, the fungus-like stramenopile, P. viticola infects grapevine
leaves through characteristic biflagellate motile zoospores released
from airborne sporangia coming from other infected plants. The
zoospores aggregate to stomata of the grapevine leaf by swimming
through water film and then rapidly encyst to become round cystospores
by shedding their flagella.3,4 The cystospores then rapidly
germinate to form germ tubes and penetrate host tissue through the
stomata. Disruption of any of these asexual stages eliminates the
potential for pathogenesis.5 The success of any zoosporic pathogen can
be attributed in part to the speed of asexual differentiation to generate
bi-flagellated motile zoospores and their ability to find a host through
chemotaxis.6 Therefore, compounds that can interfere with normal
swimming behavior and early development of P. viticola are supposed
to be important as lead compounds in the management of this
notorious phytopathogen.4
Streptomycetes are known to produce diverse groups of interesting
bioactive secondary metabolites.7 In the course of screening for
secondary metabolites from actinomycetes, we found that the crude
extract of a terrestrial Streptomyces sp. ANK313 remarkably inhibited
motility of P. viticola zoospores and caused subsequent lysis at
100 mgml_1. This observation prompted us to isolate and characterize
the motility-inhibitory and lytic factors in the extracts by chromatographic
fractionation. We have discovered a new motility inhibitor
and zoosporicide named khatmiamycin (1) along with five known
compounds from extracts of the culture broth of Streptomyces sp.
ANK313. This study describes the isolation, structure elucidation and
biological activity of khatmiamycin (1) and further known compounds
towards zoospores of Plasmopara viticola.
Description
This paper had been presented for promotion at the University of Khartoum. To get the full text please contact the other at munalsamahoni@yahoo.com
Keywords
antibacterial; naphthoquinones; oomycetes; Streptomyces; zoosporicide