AUTHOR=Ma Zongwang , Geudens Niels , Kieu Nam P. , Sinnaeve Davy , Ongena Marc , Martins José C. , Höfte Monica 

TITLE=Biosynthesis, Chemical Structure, and Structure-Activity Relationship of Orfamide Lipopeptides Produced by Pseudomonas protegens and Related Species

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00382

DOI=10.3389/fmicb.2016.00382

ISSN=1664-302X

ABSTRACT=<p>Orfamide-type cyclic lipopeptides (CLPs) are biosurfactants produced by <italic>Pseudomonas</italic> and involved in lysis of oomycete zoospores, biocontrol of <italic>Rhizoctonia</italic> and insecticidal activity against aphids. In this study, we compared the biosynthesis, structural diversity, <italic>in vitro</italic> and <italic>in planta</italic> activities of orfamides produced by rhizosphere-derived <italic>Pseudomonas protegens</italic> and related <italic>Pseudomonas</italic> species. Genetic characterization together with chemical identification revealed that the main orfamide compound produced by the <italic>P</italic>. <italic>protegens</italic> group is orfamide A, while the related strains <italic>Pseudomonas</italic> sp. CMR5c and CMR12a produce orfamide B. Comparison of orfamide fingerprints led to the discovery of two new orfamide homologs (orfamide F and orfamide G) in <italic>Pseudomonas</italic> sp. CMR5c. The structures of these two CLPs were determined by nuclear magnetic resonance (NMR) and mass spectrometry (MS) analysis. Mutagenesis and complementation showed that orfamides determine the swarming motility of parental <italic>Pseudomonas</italic> sp. strain CMR5c and their production was regulated by <italic>luxR</italic> type regulators. Orfamide A and orfamide B differ only in the identity of a single amino acid, while orfamide B and orfamide G share the same amino acid sequence but differ in length of the fatty acid part. The biological activities of orfamide A, orfamide B, and orfamide G were compared in further bioassays. The three compounds were equally active against <italic>Magnaporthe oryzae</italic> on rice, against <italic>Rhizoctonia solani</italic> AG 4-HGI in <italic>in vitro</italic> assays, and caused zoospore lysis of <italic>Phytophthora</italic> and <italic>Pythium</italic>. Furthermore, we could show that orfamides decrease blast severity in rice plants by blocking appressorium formation in <italic>M. oryzae</italic>. Taken all together, our study shows that orfamides produced by <italic>P. protegens</italic> and related species have potential in biological control of a broad spectrum of fungal plant pathogens.</p>