Characterization of hexose transporters in Yarrowia lipolytica reveals new groups of Sugar Porters involved in yeast growth

Abstract

Sugar assimilation has been intensively studied in the model yeast S. cerevisiae, and for two decades, it has been clear that the homologous HXT genes, which encode a set of hexose transporters, play a central role in this process. However, in the yeast Yarrowia lipolytica, which is well-known for its biotechnological applications, sugar assimilation is only poorly understood, even though this yeast exhibits peculiar intra-strain differences in fructose uptake: some strains (e.g., W29) are known to be slow-growing in fructose while others (e.g., H222) grow rapidly under the same conditions. Here, we retrieved 24 proteins of the Sugar Porter family from these two strains, and determined that at least six of these proteins can function as hexose transporters in the heterologous host Saccharomyces cerevisiae EBY.VW4000. Transcriptional studies and deletion analysis in Y. lipolytica indicated that two genes, YHT1 and YHT4, are probably the main players in both strains, with a similar role in the uptake of glucose, fructose, and mannose at various concentrations. The other four genes appear to constitute a set of 'reservoir' hexose transporters with an as-yet unclear physiological role. Furthermore, through examining Sugar Porters of the entire Yarrowia clade, we show that they constitute a dynamic family, within which hexose transport genes have been duplicated and lost several times. Our phylogenetic analyses support the existence of at least three distinct evolutionary groups of transporters which allow yeasts to grow on hexoses. In addition to the well-known and widespread Hxt-type transporters (which are not essential in Y. lipolytica), we highlight a second group of transporters, represented by Yht1, which are phylogenetically related to sensors that play a regulatory role in S. cerevisiae, and a third group, represented by Yht4, previously thought to contain only high-affinity glucose transporters related to Hgt1of Kluyveromyces lactis.

Alternative Substrate Metabolism in Yarrowia lipolytica

“…In Y. lipolytica , there are at least 24 sugar transporters with 6 of these being identified strictly as hexose transporters ( Lazar et al, 2017 ). These hexose transporters were identified from heterologous expression of the Y. lipolytica transporters in a knockout strain of S. cerevisiae incapable of sugar uptake.…”

Transforming sugars into fat - lipid biosynthesis using different sugars inYarrowia lipolytica

“…To minimize the number of gene deletions, the β ‐oxidation pathway was blocked by deleting the multifunctional enzyme ( ∆mfe2 ). Furthermore, glycerol‐3‐phosphate dehydrogenase ( GPD1 ) and diacylglycerol acyltransferase ( DGA1 ) were overexpressed to improve triacylglycerol biosynthesis; hexokinase ( HXK1 ) and an efficient hexose transporter ( YHT3 ; Lazar et al ., ) were also overexpressed to improve fructose utilization. Finally, the inulinase gene native to K. marxianus ( INU1 ) was introduced, allowing the strain to exploit inulin as a substrate.…”

Nitrogen as the major factor influencing gene expression in Yarrowia lipolytica

“…In almost all tested conditions, the hexose transporters YHT1 or YHT4 were differentially expressed what suggests that glucose transport is particularly susceptible to changes in carbon source quality and nitrogen availability. Further, the YHT4 was upregulated on glucose at C/N 20 as could be expected by examining the function of its product – a high affinity glucose transport [ 41 ]. It is puzzling however, that the same gene was downregulated on glucose at C/N 40 ( Fig.…”