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Xu G.,Institute of Nuclear Agricultural science | Lu H.,Institute of Nuclear Agricultural science | Wang L.,Institute of Nuclear Agricultural science | Chen H.,Institute of Nuclear Agricultural science | And 5 more authors.
DNA Repair | Year: 2010

The bacterium Deinococcus radiodurans can survive extremely high exposure to ionizing radiation. The repair mechanisms involved in this extraordinary ability are still being investigated. ddrB is one gene that is highly up-regulated after irradiation, and it has been proposed to be involved in RecA-independent repair in D. radiodurans. Here we cloned, expressed and characterized ddrB in order to define its roles in the radioresistance of D. radiodurans. DdrB preferentially binds to single-stranded DNA. Moreover, it interacts directly with single-stranded binding protein of D. radiodurans DrSSB, and stimulates single-stranded DNA annealing even in the presence of DrSSB. The post-irradiation DNA repair kinetics of a ddrB/recA double mutant were compared to ddrB and recA single mutants by pulsed-field gel electrophoresis (PFGE). DNA fragment rejoining in the ddrB/recA double mutant is severely compromised, suggesting that DdrB-mediated single-stranded annealing plays a critical role in the RecA-independent DNA repair of D. radiodurans. © 2010 Elsevier B.V. All rights reserved.

Chen H.,Institute of Nuclear Agricultural science | Chen H.,Zhejiang Institute of Microbiology | Wu R.,Second Affiliated Hospital | Xu G.,Institute of Nuclear Agricultural science | And 5 more authors.
Biochemical and Biophysical Research Communications | Year: 2010

Transcriptional regulators of the diphtheria toxin repressor (DtxR) family control the expression of genes involved in the uptake of iron and manganese, which is not only necessitous nutrients but also was suggested to be essential for intracellular redox cycling of microorganisms. We identified a unique DtxR homologue (DR2539) with special characteristics from Deinococcus radiodurans, which is known for its extreme resistance to radiation and oxidants. The dr2539 mutant showed higher resistance to hydrogen peroxide than the wild-type strain R1. Intracellular catalase activity assay and semiquantitative PCR analysis demonstrated that this DtxR is a negative regulator of catalase (katE). Furthermore, quantitative real-time PCR, global transcription profile and inductively coupled plasma-mass spectrometry analysis showed that the DtxR is involved in the regulation of antioxidant system by maintaining the intracellular Mn/Fe ion homeostasis of D. radiodurans. However, unlike the other DtxR homologues, the DtxR of D. radiodurans acts as a negative regulator of a Mn transporter gene (dr2283) and as a positive regulator of Fe-dependent transporter genes (dr1219, drb0125) in D. radiodurans. © 2010 Elsevier Inc. All rights reserved.

Jin L.,Institute of Nuclear Agricultural science | Lu Y.,Institute of Nuclear Agricultural science | Shao Y.,Institute of Nuclear Agricultural science | Zhang G.,Institute of Nuclear Agricultural science | And 4 more authors.
Journal of Cereal Science | Year: 2010

II-32B is a key maintainer line used for hybrid rice breeding in China. However, it is of poor quality for most Chinese consumers because of its high apparent amylose content (AAC), high gelatinization temperature (GT) and non-fragrance. It is well known that the AAC, GT and fragrance traits are largely controlled by the Wx, starch synthase IIa (SSIIa), and fragrance (fgr) genes, respectively. With the aid of functional markers, we improved the quality of II-32B by introgressing the Wx, SSIIa, and fgr genes from Yixiang B, a fragrant maintainer line that has low AAC and low GT. The microsatellite allele (CT)17 of Wx, the contiguous single nucleotide polymorphism TT allele of SSIIa and the 8-bp deletion allele of fgr were transferred to II-32B by two backcrosses and three selfings. Molecular marker assisted selection was applied in the series to select for individuals carrying Wx-(CT)17, SSIIa-TT, and fgr-deletion alleles. According to the marker genotypes, seventeen homozygous lines for Wx-(CT)17, SSIIa-TT, and fgr gene markers were finally selected. The improved II-32B lines were fragrant with reduced AAC and GT. © 2009 Elsevier Ltd. All rights reserved.

Zhu F.,University of Hong Kong | Zhu F.,Institute of Nuclear Agricultural science | Cai Y.-Z.,University of Hong Kong | Bao J.,Institute of Nuclear Agricultural science | Corke H.,University of Hong Kong
Food Chemistry | Year: 2010

Whole grain rice is rich in phenolic compounds. The effect of γ-irradiation on the main phenolic compounds in the rice grains of three genotypes (black, red, and white) was investigated. Three phenolic acids (p-coumaric acid, ferulic acid, and sinapinic acid) were identified as major phenolic compounds in all rice samples, while two anthocyanins (cyanidin-3-glucoside and peonidin-3-glucoside) were identified in pigmented grain samples. In general, γ-irradiation at most of doses could significantly (p < 0.05) decrease total phenolic acid contents in all samples and total anthocyanins contents in the black rice, but their decreases were not completely in a dose-dependent manner. Unexpectedly, 6 and 8 kGy significantly (p < 0.05) increased total contents of anthocyanins and phenolic acids in black rice. This study suggested that suitable doses of irradiation might be carefully selected and used to minimise the loss of antioxidant phenolic compounds in whole grain rice during storage. © 2009 Elsevier Ltd. All rights reserved.

Haiyan W.,Institute of Nuclear Agricultural science | Zhiyang Y.,Institute of Nuclear Agricultural science | Ling Y.,Institute of Nuclear Agricultural science | Ailiang H.,Institute of Nuclear Agricultural science | And 5 more authors.
Science of the Total Environment | Year: 2010

A soil metabolism study of propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273), a novel broad-spectrum herbicide, was carried out using 14C labeled on two different rings, i.e., [pyrimidine-4,6-14C] ZJ0273 and [benzyl-U-14C] ZJ0273. Ultralow liquid scintillation counting and LC-MS/MS were used to identify the degradation intermediates and quantify their dynamics in aerobic soils. Four aromatic intermediates, 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoic acid (M1), 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzamido)benzoic acid (M2), 2-(4,6-dimethoxypyrimidin-2-yloxy)benzoic acid (M3), and 4,6-dimethoxypyrimidin-2-ol (M4), were identified and their identity was further confirmed against authentic standards. Analysis of metabolites suggested two degradation pathways: (1) Upon loss of the propyl group, M1 was produced via hydrolysis of propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate after which the C-N bond between rings A and B was cleaved by oxidation and biochemical degradation to yield M3, which was further converted into M4 and finally mineralized to CO2; and (2) the first step was the same as in pathway 1, but M1 first underwent a carbonylation to form M2. The C-N bond between rings A and B of M2 was cleaved by hydrolysis to yield M3. Dynamic changes in the four metabolites in aerobic soils were also investigated by HPLC coupled analysis of radioactivity of isolated peaks. After a 100-day incubation, 1.7-9.7% of applied 14C was found as M1, 0.3-1.1% as M2, 14.5-20.9% as M3, and 3.7-6.7% as M4 in the soils, and pH appeared to be the most influential soil property affecting the formation and dissipation of these metabolites. © 2010 Elsevier B.V. All rights reserved.

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