Aromatic Polyketides from a Symbiotic Strain Aspergillus fumigatus D and Characterization of Their Biosynthetic Gene D8.t287

Abstract

The chemical investigation of one symbiotic strain, <i>Aspergillus fumigatus</i> D, from the coastal plant <i>Edgeworthia chrysantha</i> Lindl led to the isolation of eight compounds (<b>1</b>-<b>8</b>), which were respectively identified as rubrofusarin B (<b>1</b>), alternariol 9-<i>O</i>-methyl ether (<b>2</b>), fonsecinone D (<b>3</b>), asperpyrone A (<b>4</b>), asperpyrone D (<b>5</b>), fonsecinone B (<b>6</b>), fonsecinone A (<b>7</b>), and aurasperone A (<b>8</b>) by a combination of spectroscopic methods (1D NMR and ESI-MS) as well as by comparison with the literature data. An antimicrobial assay showed that these aromatic polyketides exhibited no remarkable inhibitory effect on <i>Escherichia coli</i>, <i>Staphyloccocus aureus</i> and <i>Candida albicans</i>. The genomic feature of strain D was analyzed, as well as its biosynthetic gene clusters, using antibiotics and Secondary Metabolite Analysis Shell 5.1.2 (antiSMASH). Plausible biosynthetic pathways for dimeric naphtho-<i>γ</i>-pyrones <b>3</b>-<b>8</b> were first proposed in this work. A non-reducing polyketide synthase (PKS) gene <i>D8.t287</i> responsible for the biosynthesis of these aromatic polyketides <b>1</b>-<b>8</b> was identified and characterized by target gene knockout experiment and UPLC-MS analysis.