Protective role of trehalose during radiation and heavy metal stress in Aureobasidium subglaciale F134

Tingting Liu,Liying Zhu,Zhidong Zhang,He Huang,Ling Jiang,Zhiping Zhang

doi:10.1038/s41598-017-15489-0

Tingting Liu, Liying Zhu + Show 4 more

Open Access

https://doi.org/10.1038/s41598-017-15489-0

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Abstract

An isolated black yeast-like strain was obtained from radiation-polluted soil collected from Xinjiang province in northwest China. On the basis of ITS and LSU rDNA sequence analysis, in combination with the colony morphology and phenotypic properties, the isolated strain was revealed to represent a novel variety of Aureobasidium subglaciale, designated as A. subglaciale F134. Compared to other yeasts and bacteria, this isolate displayed superior resistance to gamma irradiation, UV light, and heavy metal ions. It was discovered that the resistance of the isolate was correlated with the stress protector trehalose. Through the overexpression of the trehalose-6-phosphate synthase gene tps1 and the deletion of acid trehalase gene ath1, the APT∆A double mutant exhibited a survival rate of 1% under 20 kGy of gamma-radiation, 2% survival rate at a UV dosage of 250 J/m2, and tolerance towards Pb2+ as high as 1500 mg/L, which was in agreement with the high accumulation of intracellular trehalose compared to the wild-type strain. Finally, the protective effects and the mechanism of trehalose accumulation in A. subglaciale F134 were investigated, revealing a significant activation of the expression of many of the stress tolerance genes, offering new perspectives on the adaptations of radioresistant microorganisms.

Highlights

The production and testing of nuclear weapons will release radioactive waste into the environment, which are contaminating the ground and subsurface at thousands of sites
According to the similarity matrix based on the alignment of all cited representative LSU rRNA gene sequences, a high level of support indicated that the strain was closely related to A. subglaciale, which is member of the secondary clade and shared a 85% homology with A. subglaciale EXF-2510 (FJ150938), A. subglaciale EXF-2481T (FJ150913) and A. subglaciale EXF-3640 (FJ150939)
We proposed to name this isolated strain of Aureobasidium as A. subglaciale F134, which could be readily distinguished from the type strain of A. pullulans[16] by a combination of phenotypic properties (Table S1)

Summary

Introduction

The production and testing of nuclear weapons will release radioactive waste into the environment, which are contaminating the ground and subsurface at thousands of sites. In China, the largest nuclear test to date was conducted on 21 May 1992 in the Kuruktag and Kyzyltag mountains of Xinjiang Uyghur Autonomous Region, with pollution covering large areas of the surface and underground. These highly toxic waste sites become the ideal places to search for radiation resistant microorganisms[1]. Trehalose is a naturally stable, non-reducing disaccharide sugar, in which two glucose units are linked via an α,α-(1,1)-glycosidic bond[11] It has been isolated from a large number of prokaryotic and eukaryotic species spanning bacteria, archaea, yeast, fungi, algae, plant, as well as low orders of the animal kingdom, especially those living in extreme environments[12]. The mutant strain showed a 3-fold increase in biosynthesis of trehalose, and displayed enhanced resistance characteristics, confirming that there is an interplay between trehalose metabolism and the oxidative stress response in Aureobasidium

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