Isolation and characterization of a reducing polyketide synthase gene from the lichen-forming fungus Usnea longissima

Abstract

The reducing polyketide synthases found in filamentous fungi are involved in the biosynthesis of many drugs and toxins. Lichens produce bioactive polyketides, but the roles of reducing polyketide synthases in lichens remain to be clearly elucidated. In this study, a reducing polyketide synthase gene (U1PKS3) was isolated and characterized from a cultured mycobiont of Usnea longissima. Complete sequence information regarding U1PKS3 (6,519 bp) was obtained by screening a fosmid genomic library. A U1PKS3 sequence analysis suggested that it contains features of a reducing fungal type I polyketide synthase with β-ketoacyl synthase (KS), acyltransferase (AT), dehydratase (DH), enoyl reductase (ER), ketoacyl reducatse (KR), and acyl carrier protein (ACP) domains. This domain structure was similar to the structure of ccRadsl, which is known to be involved in resorcylic acid lactone biosynthesis in Chaetomium chiversii. The results of phylogenetic analysis located U1PKS3 in the clade of reducing polyketide synthases. RT-PCR analysis results demonstrated that UIPKS3 had six intervening introns and that UIPKS3 expression was upregulated by glucose, sorbitol, inositol, and mannitol.

Three New Non-reducing Polyketide Synthase Genes from the Lichen-Forming Fungus Usnea longissima

“…In a previous study, we reported two PKSs, a NR-PKS and a reducing PKS, from U. longissima [20, 21]. In the present study, we report three additional novel NR-PKSs, which may be involved in the biosynthesis of orcinol and β-orcinol depside or depsidone.…”

“…U. longissima LFF used in this study had been previously identified and deposited at the Korea Lichen and Allied Bioresearch Center, Sunchon National University [20]. The LFF was grown and maintained in malt-yeast (MY) medium (Difco, Detroit, MI, USA).…”

Identification of a putative polyketide synthase gene involved in usnic acid biosynthesis in the lichen Nephromopsis pallescens

“…Although several PKS genes have been cloned from lichen-forming fungi [ 16 – 18 ], functional characterizations of PKS have been limited to bioinformatics approaches. Some researchers have attempted the heterologous expression of lichen PKS [ 16 , 19 , 20 ], but were unable to demonstrate de novo biosynthesis of a lichen metabolite. However, two research teams have used qRT-PCR and HPLC techniques to show that putative PKS-related genes are associated with the biosynthesis of target lichen metabolites [ 10 , 21 ].…”

In vitrorisk assessment of usnic acid

“…Lichen secondary metabolites are mainly produced by the fungal partner organized into several distinct chemical classes such as depsides, depsidones, dibenzofurans, xanthones, terpene derivatives, and so on. (Johnson et al, 2011; Manojlovic et al, 2012; Wang et al, 2011). Lichens and their secondary metabolites were effective in the treatment of diseases such as hemorrhoids, bronchitis, dysentery, and tuberculosis (Gülçin et al, 2012).…”