Identification of extracellular siderophores and a related peptide from the endophytic fungus Epichlo? festucae in culture and endophyte-infected Lolium perenne

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• 作者：Albert Koulman^a ; T. Verne Lee^b ; Karl Fraser^c ; Linda Johnson^c ; Vickery Arcus^d ; J. Shaun Lott^b ; Susanne Rasmussen^c ; Geoffrey Lane^c ; ^{Geoff.Lane@agresearch.co.nz}
• 关键词：Epichloë ; festucae ; Clavicipitaceae ; Lolium perenne ; Poaceae ; Siderophore ; Cyclic peptide ; LC-MSn ; High resolution MSn (HRMSn) ; NMR
• 刊名：Phytochemistry
• 出版年：2012
• 出版时间：March, 2012
• 年：2012
• 卷：75
• 期：Complete
• 页码：128-139
• 全文大小：813 K

文摘

A number of genes encoding non-ribosomal peptide synthetases (NRPSs) have been identified in fungi of Epichlo?/Neotyphodium species, endophytes of Pooid grasses, including sidN, putatively encoding a ferrichrome siderophore-synthesizing NRPS. Targeted gene replacement and complementation of sidN in Epichlo? festucae has established that extracellular siderophore epichlo?nin A is the major product of the SidN enzyme complex (). We report here high resolution mass spectrometric fragmentation experiments and NMR analysis of an isolated fraction establishing that epichlo?nin A is a siderophore of the ferrichrome family, comprising a cyclic sequence of four glycines, a glutamine and three N^¦Ä-trans-anhydromevalonyl-N^¦Ä-hydroxyornithine (AMHO) moieties. Epichlo?nin A is unusual among ferrichrome siderophores in comprising an octapeptide rather than hexapeptide sequence, and in incorporating a glutamine residue. During this investigation we have established that desferrichrome siderophores with pendant trans-AMHO groups can be distinguished from those with pendant cis-AMHO groups by the characteristic neutral loss of an hydroxyornithine moiety in the MS/MS spectrum. A minor component, epichlo?nin B, has been characterized as the triglycine variant by mass spectrometry. A peptide characterized by mass spectrometry as the putative deoxygenation product, epichlo?amide has been detected together with ferriepichlo?nin A in guttation fluid from ryegrass (Lolium perenne) plants infected with wild-type E. festucae, but not in plants infected with the ¦¤sidN mutant strain, and also detected at trace levels in wild-type E. festucae fungal culture.