TFAM, a potential oxidative stress biomarker used for monitoring environment pollutants in Musca domestica.

Mitochondrial transcription factor A (TFAM) plays a key role in regulating the transcription, replication, and maintenance of mitochondrial DNA. In the present study, a Musca domestica TFAM (MdTFAM) gene was identified and characterized. MdTFAM gene encodes 253 amino acid residues, and the protein possesses two conserved motifs of HMG (High Mobility Group) box. Expression of MdTFAM was investigated based on the qRT-PCR (quantitative real-time polymerase chain reaction) in response to three model oxidative stress-inducing agents, cadmium chloride (Cd), doxorubicin hydrochloride (DOX) and ultraviolet (UV), respectively. Results showed that Cd exposure not only generated oxidative stress and mitochondrial dysfunctions in M. domestica larvae, with a significant increase in malondialdehyde and reactive oxygen species levels, but also induced a dose-dependent increase in the expression of MdTFAM. In addition, either DOX or UV exposure also significantly up-regulated the expression of MdTFAM in M. domestica larvae. These results suggest that MdTFAM play a vital role in maintaining the redox balance and its expression may serve as a useful biomarker for monitoring the oxidative stress induced by Cd, DOX or UV.

Polydatin attenuates cadmium-induced oxidative stress via stimulating SOD activity and regulating mitochondrial function in Musca domestica larvae.

Cadmium (Cd) is a widespread environment contaminant due to the development of electroplating and metallurgical industry. Cd can be enriched by organisms via food chain, causing the enlarged environmental problems and posing threats to the health of humans. Polydatin (PD), a natural stilbenoid compound derived from Polygonum cuspidatum, shows pronouncedly curative effect on oxidative damage. In this work, the protective effects of PD on oxidative damage induced by Cd in Musca domestica (housefly) larvae were evaluated. The larvae were exposed to Cd and/or PD, subsequently, the oxidative stress status, mitochondria activity, oxidative phosphorylation efficiency, and survival rate were assessed. Cd exposure generated significant increases of malondialdehyde (MDA), reactive oxygen species (ROS) and 8-hydroxy-2-deoxyguanosine (8-oxoG) in the housefly larvae, causing mitochondrial dysfunction and survival rate decline. Interestingly, pretreatment with PD exhibited obviously mitochondrial protective effects in the Cd-exposed larvae, as evidenced by reduced MDA, ROS and 8-oxoG levels, and increased activities of superoxide dismutase (SOD), mitochondrial electron transfer chain, and mitochondrial membrane potential, as well as respiratory control ratio. These results suggested that PD could attenuate Cd-induced damage via maintaining redox balance, stimulating SOD activity, and regulating mitochondria activity in housefly larvae. As a natural polyphenolic chemical, PD can act as a potential candidate compounds to relieve Cd injury.

Heterologous expression and biochemical characterization of a thermostable xylulose kinase from Bacillus coagulans IPE22.

Xylulose kinase is an important enzyme involved in xylose metabolism, which is considered as essential biocatalyst for sustainable lignocellulosic-derived pentose utilization. Bacillus coagulans IPE22 is an ideal bacterium for refinery due to its strong ability to ferment xylose at high temperature. However, the B. coagulans xylose utilization mechanism remains unclear and the related promising enzymes need to be developed. In the present study, the gene coding for xylulose kinase from B. coagulans IPE22 (Bc-XK) was expressed in Escherichia coli BL21 (DE3). Bc-XK has a 1536 bp open reading frame, encoding a protein of 511 amino acids (56.15 kDa). Multiple sequence alignments were performed and a phylogenetic tree was built to evaluate differences among Bc-XK and other bacteria homologs. Bc-XK showed a broad adaptability to high temperature and the enzyme displayed its best performance at pH 8.0 and 60 °C. Bc-XK was activated by Mg2+ , Mn2+ , and Co2+ . Meanwhile, the enzyme could keep activity at 60 °C for at least 180 min. KM values of Bc-XK for xylulose and ATP were 1.29 mM and 0.76 mM, respectively. The high temperature stability of Bc-XK implied that it was an attractive candidate for industrial application.