Moesziomyces antarcticus MMF1 Has a Role in the Secretion of Mannosylerythritol Lipids

Mannosyl erythritol lipids (MELs) are glycolipid biosurfactants produced by <i>Ustilaginomycete</i> yeasts. The MEL biosynthetic pathway has been characterized in <i>Ustilago maydis</i> where a putative transporter encoded by <i>MMF1</i> is required for the secretion of the glycolipid surfactant to the extracellular space. The anamorphic yeast <i>Moesziomyces antarcticus</i> is a prolific producer of MELs, but the mechanism of MEL secretion is less well characterized than in <i>U. maydis</i>. Homologous recombination was employed to generate a disruption of the <i>MMF1</i> gene in <i>M. antarcticus</i> JCM10317. This mutation did not prevent the intracellular accumulation of MEL species but did result in significantly reduced secretion of the conventional MEL-A, MEL-B and MEL-C species detectable by thin-layer chromatography. However, the mutant strain did secrete a glycolipid species that is distinct from conventional MEL-A/B/C and similar to a glycolipid secreted by <i>MMF1</i> mutant strains of <i>U. maydis</i> and <i>Pseudozyma tsukubaensis</i>. Despite the defect in MEL secretion displayed by the <i>M. antarcticus</i> strain harbouring a disrupted <i>MMF1</i> gene, these cells did not display a significant defect in growth or cell morphology. The findings of this investigation provide evidence that <i>M. antarcticus MMF1</i> encodes a transporter required for the secretion of MELs but not required for MEL synthesis or cell growth.