Genomic and transcriptomic analysis of reveals the genetic determinants for its xylose-converting capacity.

BACKGROUND

An economically viable production of biofuels and biochemicals from lignocellulose requires microorganisms that can readily convert both the cellulosic and hemicellulosic fractions into product. The yeast displays a high capacity for uptake and conversion of several lignocellulosic sugars including the abundant pentose d-xylose, an underutilized carbon source since most industrially relevant microorganisms cannot naturally ferment it. Thus, constitutes an important source of knowledge and genetic information that could be transferred to industrial microorganisms such as to improve their capacity to ferment lignocellulose-derived xylose.

RESULTS

To understand the genetic determinants that underlie the metabolic properties of , we sequenced the genomes of both the in-house-isolated strain CBS 141442 and the reference strain PYCC 4715. De novo genome assembly and subsequent analysis revealed to be a haploid species belonging to the CTG clade of yeasts. The two strains have highly similar genome sizes and number of protein-encoding genes, but they differ on the chromosomal level due to numerous translocations of large and small genomic segments. The transcriptional profiles for CBS 141442 grown in medium with either high or low concentrations of glucose and xylose were determined through RNA-sequencing analysis, revealing distinct clusters of co-regulated genes in response to different specific growth rates, carbon sources and osmotic stress. Analysis of the genomic and transcriptomic data also identified multiple xylose reductases, one of which displayed dual NADH/NADPH co-factor specificity that likely plays an important role for co-factor recycling during xylose fermentation.

CONCLUSIONS

In the present study, we performed the first genomic and transcriptomic analysis of and identified several novel genes for conversion of xylose. Together the results provide insights into the mechanisms underlying saccharide utilization in and reveal potential target genes to aid in xylose fermentation in .