Fig 1.
Biosynthetic pathway for mannosylerythritol lipids.
Emt1p: mannose/erythritol transferase; Mac1p and Mac2p: acyl-transferases; Mat1p: acetyl-transferase; Mmf1p: predicted MEL transporter.
Fig 2.
Gene clusters of mannosylerythritol lipid (MEL) biosynthesis and gene expression profiles.
The MEL biosynthesis gene cluster in U. maydis UM521 and P. antarctica T-34 (A). Two-dimensional histogram showing the gene expression distribution (A-value, ordinate) and gene transcription induction ratio (M-value, abscissa) in the presence of vegetable oil and glucose in P. antarctica T-34 (B) and U. maydis UM521 (C). The number of genes is represented by the gray shading of each hexagonal cell. This hexplot was drawn using the hexbin module in R [21]. The genes responsible for MEL biosynthesis are overlaid on the hexplot in pink.
Table 1.
KOG classification of 264 genes extracted by guilt-by-association.
Fig 3.
Induction of genes responsible for oil degradation and conversion and primary metabolism.
The M-value averages of the genes responsible for MEL biosynthesis, mitochondrial beta-oxidation, peroxisomal beta-oxidation, fatty acid synthesis, glycolysis, tricarboxylic acid cycle, pentose phosphate pathway, and malate/pyruvate cycle are shown in orange (U. maydis UM521) and blue (P. antarctica T-34).
Fig 4.
M-values in the central metabolic pathway of P. antarctica T-34 and U. maydis UM521.
Comparison of the expression profiles of genes encoding enzymes that participate in glycolysis and the tricarboxylic acid cycle under oily conditions in P. antarctica T-34 (A) and U. maydis UM521 (B). To facilitate the comparison of the two microorganisms, portions of the metabolic pathways of Saccharomyces cerevisiae are presented, and the behaviors of genes encoding the enzymes that catalyze each step were estimated. GUT: glycerol-3-phosphate dehydrogenase; TPI: triose phosphate isomerase; FBA: fructose 1,6-bisphosphate aldolase; TDH: glyceraldehyde-3-phosphate dehydrogenase; PGK: 3-phosphoglycerate kinase; GPM: phosphoglycerate mutase; ENO: enolase; PYK: pyruvate kinase; PDA: pyruvate dehydrogenase; PDC: pyruvate decarboxylase; ACS: acetyl-coA synthetase; ADH: alcohol dehydrogenase; ALD: aldehyde dehydrogenase; PCK: phosphoenolpyruvate carboxykinase; MAE: malic enzyme; CIT: citrate synthase; ACO: aconitase; IDH: isocitrate dehydrogenase; KGD: α-ketoglutarate dehydrogenase; LSC: succinyl-CoA ligase; SDH: succinate dehydrogenase; FUM: fumarate hydratase; MDH: malate dehydrogenase; ICL: isocitrate lyase; MAS: malate synthase. Red and green boxes represent those genes whose expression levels were increased and decreased, respectively, under oily conditions.
Fig 5.
Comparison of mannosylerythritol lipid (MEL) production, cell growth, and isocitrate dehydrogenase (NAD+) activity of P. antarctica T-34 and U. maydis UM521 in the presence of glucose or soybean oil as the sole carbon source.
(A) MELs were extracted from the culture after 3 and 5 days using an equal amount of ethyl acetate, and the organic solvent fractions (with glucose: 10 μL, with soybean oil: 2.5 μL) were spotted on a TLC plate. A typical sample of three independent experiments was shown in each lane. Spots were visualized using the anthrone reagent. Purified MEL-A, MEL-B, and MEL-C were used as standards. (B) The weight of wet cells was measured to estimate growth. (C) The activity of isocitrate dehydrogenase (NAD+) was measured as described in the Materials and methods section. Error bars show standard deviations.