Identification of a Gene Cluster for Biosynthesis of Mannosylerythritol Lipids in the Basidiomycetous Fungus Ustilago maydis

Abstract

Many microorganisms produce surface-active substances that enhance the availability of water-insoluble substrates. Although many of these biosurfactants have interesting potential applications, very little is known about their biosynthesis. The basidiomycetous fungus Ustilago maydis secretes large amounts of mannosylerythritol lipids (MELs) under conditions of nitrogen starvation. We recently described a putative glycosyltransferase, Emt1, which is essential for MEL biosynthesis and whose expression is strongly induced by nitrogen limitation. We used DNA microarray analysis to identify additional genes involved in MEL biosynthesis. Here we show that emt1 is part of a gene cluster which comprises five open reading frames. Three of the newly identified proteins, Mac1, Mac2, and Mat1, contain short sequence motifs characteristic for acyl-and acetyltransferases. Mutational analysis revealed that Mac1 and Mac2 are essential for MEL production, which suggests that they are involved in the acylation of mannosylerythritol. Deletion of mat1 resulted in the secretion of completely deacetylated MELs, as determined by mass spectrometry. We overexpressed Mat1 in Escherichia coli and demonstrated that this enzyme acts as an acetyl coenzyme A-dependent acetyltransferase. Remarkably, Mat1 displays relaxed regioselectivity and is able to acetylate mannosylerythritol at both the C-4 and C-6 hydroxyl groups. Based on these results, we propose a biosynthesis pathway for the generation of mannosylerythritol lipids in U. maydis.

Metabolome and Transcriptome of the Interaction between Ustilago maydis and Fusarium verticillioides In Vitro

“…Even though we could not de- tect the metabolite MEL in the liquid culture with the sampling techniques we used, we did find expression of genes involved in MEL biosynthesis (10). As seen with ustilagic acid, expression of the genes involved in MEL biosynthesis is detected in single cultures after 2 days but almost completely absent in cocultivation cultures (Fig.…”

Nitrogen Source Affects Glycolipid Production and Lipid Accumulation in the Phytopathogen Fungus <i>Ustilago maydis</i>

“…The longest lipid moiety of ustilagic acid has been reported to hydroxilated C16:0 but for mannosylerytritol lipids C 14 , C 16 and C 18 saturated and unsaturated fatty acids were found although sucrose was the carbon source [8] [33]. The enzymes involved in the biosynthesis of the glycolipids (UA and MEL) have been described in [11] [12]. For UA a cytochrome P450 monooxygenase Cyp1 catalyzes terminal hydroxylation of palmitic acid and cyp2 is required for subterminal hydroxylation (w-1 hydroxylation) of this fatty acid [1] [12].…”

“…For UA, cyp1 and cyp2 genes are required for terminal and subterminal hydroxylation of hexadecanoic acid [12]. Mannosylerythritol lipids (MEL) are secreted in at least four different varieties (ABCD), depending on the number of acetyl groups attached to the disaccharide [3]- [11] and a glycosyltransferase is essential for the biosynthesis of MEL; expression of this enzyme is strongly induced by limitations on nitrogen availability [11]. To produce these glycolipids, U. maydis requires raw materials to synthesize the lipid and carbohydrate moieties.…”

Gene expression associated with vegetative incompatibility in Amylostereum areolatum

“…Several of the identified ESTs encoded putative proteins that are directly involved in the sensing of stress and in the defence response (Iakovlev and Stenlid, 2000;Kültz, 2005;Horan et al, 2006;Gucciardo et al, 2007). Proteins known to be involved in the nutrient starvation response (Schmelzle et al, 2004;Aro et al, 2005, Hewald et al, 2006 were also identified, which is comparable to that found in P. anserina (Federovo et al, 2005;Pinan-Lucarré et al, 2003, 2007. qRT-PCR analyses on A. areolatum made it possible to further show that transcripts encoding putative defence response proteins were strongly up-regulated only in the vegetatively incompatibile interactions, while the results of the laccase staining experiments showed that laccases most likely contribute to the protection of cells (Eisenman et al, 2007) during vegetatively incompatibility.…”