Genetic analysis of D-xylose metabolism by endophytic yeast strains of Rhodotorula graminis and Rhodotorula mucilaginosa

Abstract

Two novel endophytic yeast strains, WP1 and PTD3, isolated from within the stems of poplar (Populus) trees, were genetically characterized with respect to their xylose metabolism genes. These two strains, belonging to the species Rhodotorula graminis and R. mucilaginosa, respectively, utilize both hexose and pentose sugars, including the common plant pentose sugar, D-xylose. The xylose reductase (XYL1) and xylitol dehydrogenase (XYL2) genes were cloned and characterized. The derived amino acid sequences of xylose reductase (XR) and xylose dehydrogenase (XDH) were 32%∼41% homologous to those of Pichia stipitis and Candida. spp., two species known to utilize xylose. The derived XR and XDH sequences of WP1 and PTD3 had higher homology (73% and 69% identity) with each other. WP1 and PTD3 were grown in single sugar and mixed sugar media to analyze the XYL1 and XYL2 gene regulation mechanisms. Our results revealed that for both strains, the gene expression is induced by D-xylose, and that in PTD3 the expression was not repressed by glucose in the presence of xylose.

Complete Utilization of the Major Carbon Sources Present in Sugar Beet Pulp Hydrolysates by the Oleaginous Red Yeasts Rhodotorula toruloides and R. mucilaginosa

“…Therefore, the efficiency of the d -galacturonic acid catabolic pathway in yeasts and filamentous fungi relies on the regeneration of the redox cofactor NADPH, which can occur through the oxidative phase of the pentose phosphate pathway (PPP) [ 62 ]. Moreover, in yeasts and filamentous fungi, the pentoses arabinose and xylose are also catabolized through the oxidoreductase pathway which also requires the redox co-factors NADPH and NADH [ 63 , 64 ]. Redox homeostasis is an essential requirement for metabolism maintenance and energy generation due to the involvement of NAD(H) and NADP(H) redox cofactors in several metabolic networks, and in particular, for both d -galacturonic acid and l- arabinose utilization.…”

Litchi chinensis seed prevents obesity and modulates the gut microbiota and mycobiota compositions in high-fat diet-induced obese zebrafish

“…58 Rhodotorula graminis is reported to metabolize sugars such as pentose and xylose. 59,60 The increased proportion of Rhodotorula graminis in the HLSE and HLSW groups may be related to the high sugar content in LSE and LSW. The HLSW group showed an increase in the proportion of Trichoderma, which produces a variety of bioactive secondary metabolites, exhibiting anti-inflammatory, anti-microbial, and anti-tumor activities.…”

Genome sequence of the plant growth promoting endophytic yeast Rhodotorula graminis WP1

“…Although originally isolated from poplar, WP1 has a broad host range, providing growth benefits not only to poplar (Knoth et al, 2014 ; Khan et al in review) but also to grasses and agricultural crop species (Khan et al, 2012 ; Knoth et al, 2013 ). Strain WP1 improves plant vigor and has useful biochemical properties (Doty, 2014 ) including the ability to ferment both pentoses and hexoses and to degrade fermentation inhibitors (Xu et al, 2011 ). Genomic analysis of bacterial endophytes has revealed certain features in common including genes for phytohormone synthesis, adhesion, colonization, stress reduction, and iron and phosphate acquisition (Fouts et al, 2008 ; Taghavi et al, 2010 ; Sessitsch et al, 2012 ; Witzel et al, 2012 ).…”