BioMetals (v.27, #2)
The diversity of nitric oxide function in plant responses to metal stress by Huyi He; Longfei He; Minghua Gu (219-228).
Nitric oxide (NO) emerges as signalling molecule, which is involved in diverse physiological processes in plants. High mobility metal interferes with NO signaling. The exogenous NO alleviates metal stress, whereas endogenous NO contributes to metal toxicity in plants. Owing to different cellular localization and concentration, NO may act as multifunctional regulator in plant responses to metal stress. It not only plays a crucial role in the regulation of gene expression, but serves as a long-distance signal. Through tight modulation of redox signaling, the integration among NO, reactive oxygen species and stress-related hormones in plants determines whether plants stimulate death pathway or activate survival signaling.
Keywords: Nitric oxide; Metal stress; Reactive oxygen species; Hormones; Cross talk; Programmed cell death
Iron and zinc binding activity of Escherichia coli topoisomerase I homolog YrdD by Zishuo Cheng; Guoqiang Tan; Wu Wang; Xiaolu Su; Aaron P. Landry; Jianxin Lu; Huangen Ding (229-236).
YrdD, a homolog of the C-terminal zinc-binding region of Escherichia coli topoisomerase I, is highly conserved among proteobacteria and enterobacteria. However, the function of YrdD remains elusive. Here we report that YrdD purified from E. coli cells grown in LB media contains both zinc and iron. Supplement of exogenous zinc in the medium abolishes the iron binding of YrdD in E. coli cells, indicating that iron and zinc may compete for the same metal binding sites in the protein. While the zinc-bound YrdD is able to bind single-stranded (ss) DNA and protect ssDNA from the DNase I digestion in vitro, the iron-bound YrdD has very little or no binding activity for ssDNA, suggesting that the zinc-bound YrdD may have an important role in DNA repair by interacting with ssDNA in cells.
Keywords: YrdD; Topoisomerase I; Zinc; Iron; Metalloprotein
Tellurite reduction by Escherichia coli NDH-II dehydrogenase results in superoxide production in membranes of toxicant-exposed cells by Waldo A. Díaz-Vásquez; María J. Abarca-Lagunas; Felipe A. Arenas; Camilo A. Pinto; Fabián A. Cornejo; Poorna T. Wansapura; Gayan A. Appuhamillage; Thomas G. Chasteen; Claudio C. Vásquez (237-246).
Tellurite, the most soluble tellurium oxyanion, is extremely harmful for most microorganisms. Part of this toxicity is due to the generation of reactive oxygen species that in turn cause oxidative stress. However, the way in which tellurite interferes with cellular processes is not well understood to date. Looking for new cellular tellurite targets, we decided to evaluate the functioning of the electron transport chain in tellurite-exposed cells. In this communication we show that the E. coli ndh gene, encoding NDH-II dehydrogenase, is significantly induced in toxicant-exposed cells and that the enzyme displays tellurite-reducing activity that results in increased superoxide levels in vitro.
Keywords: Tellurite; Tellurite reductase; NDH-II; Superoxide; Electron transport chain; Escherichia coli
Evidences for structural basis of altered ascorbate peroxidase activity in cadmium-stressed rice plants exposed to jasmonate by Indra Singh; Kavita Shah (247-263).
Binding interactions of cadmium (Cd) with rice ascorbate peroxidase (OsAPX) in presence or absence of jasmonate was examined in-silico. OsAPX is a 250 amino acid long protein with 90 % sequence similarity to soybean-APX. The 3D model of OsAPX obtained by homology modeling using soybean APX (PDBID:1OAF) as template was associated with −15975.85 kJ/mol energy, 100 % residues in favoured region, verify score of 0.85, ERRAT score 89.625 and a negative ProSA graph, suggesting OsAPX model to be of good quality, robust and reliable which was submitted with Protein Model Database with PMDBID: PM0078091. The rice ascorbate peroxidase ascorbate [OsAPX–Asc] complex had a substrate binding cavity involving residues at position 30KSCAPL35, 167RCH169 and 172R wherein ascorbate accommodated via three H-bonds involving 30Lys at the γ-edge of heme. 169His served as a bridge between heme-porphyrin of OsAPX and ascorbate creating a charge relay system. Cd bound in [OsAPX–Asc–Cd] complex at 29EKSCAPL35, a site similar to ascorbate binding site. The binding of Cd caused breaking of 169His bridge shifting the protein conformation. Cadmium exhibited four electrostatic interactions via 29Glu of OsAPX backbone. Docking of [OsAPX–Asc] with jasmonic acid (JA) resulted in [OsAPX–Asc–JA] complex where 4—H-bonds held JA to OsAPX in a cavity at γ-edge on the distal side of heme. The binding of [OsAPX–Asc–JA] to Cd show the metal to bind at a position other than that involved in binding of OsAPX with Cd alone. Results indicate that Cd does not replace iron or ascorbate or JA but binds to OsAPX on the surface at a separate site electrostatically. In presence of JA the interactions involved in formation of [OsAPXAsc] are restored which is otherwise altered by the presence of Cd. The formation and reformation of H-bond take place between the [OsAPX–Asc] and Cd/JA. It is the interaction between heme and ascorbate which is modulated differently in presence of Cd/JA. In absence of JA, Cd-binds to the [OsAPX–Asc] complex at the proximal end of APX near Asc-binding site, whereas in presence of JA, Cd-binds on the opposite site of the Asc-binding site involving 30Lys and 29Glu residues. In-silico binding studies well correlate with the wet-lab results where exogenous application of JA increased the activity of OsAPX in rice grown under Cd-stress. Therefore it is concluded that the activity of OsAPX in rice roots and shoots are compromised under Cd-stress alone.
Keywords: Ascorbate peroxidase; Cadmium; Homology modelling; Jasmonate; Rice
Proteomic analysis of copper-binding proteins in excess copper-stressed rice roots by immobilized metal affinity chromatography and two-dimensional electrophoresis by Yufeng Song; Hongxiao Zhang; Chen Chen; Guiping Wang; Kai Zhuang; Jin Cui; Zhenguo Shen (265-276).
Copper (Cu) is an essential micronutrient required for plant growth and development. However, excess Cu can inactivate and disturb protein structure as a result of unavoidable binding to proteins. To understand better the mechanisms involved in Cu toxicity and tolerance in plants, we developed a new immobilized metal affinity chromatography (IMAC) method for the separation and isolation of Cu-binding proteins extracted from roots of rice seedling exposed to excess Cu. In our method, IDA-Sepharose or EDDS-Sepharose column (referred as pre-chromatography) and Cu-IDA-Sepharose column (referred as Cu-IMAC) were connected in tandem. Namely, protein samples were pre-chromatographed with IDA-Sepharose column to removal metal ions, then protein solution was flowed into Cu-IMAC column for enriching Cu-binding proteins in vitro. Compared with the control (Cu-IMAC without any pre-chromatography), IDA-Sepharose pre-chromatography method markedly increased yield of the Cu-IMAC-binding proteins, and number of protein spots and the abundance of 40 protein spots on two-dimensional electrophoresis (2-DE) gels. Thirteen protein spots randomly selected from 2-DE gel and 11 proteins were identified using MALDI-TOF-TOF MS. These putative Cu-binding proteins included those involved in antioxidant defense, carbohydrate metabolism, nucleic acid metabolism, protein folding and stabilization, protein transport and cell wall synthesis. Ten proteins contained one or more of nine putative metal-binding motifs reported by Smith et al. (J Proteome Res 3:834–840, 2004) and seven proteins contained one or two of top six motifs reported by Kung et al. (Proteomics 6:2746–2758, 2006). Results demonstrated that more proteins specifically bound with Cu-IMAC could be enriched through removal of metal ions from samples by IDA-Sepharose pre-chromatography. Further studies are needed on metal-binding characteristics of these proteins in vivo and the relationship between Cu ions and protein biological activities to fully understand the mechanisms of Cu tolerance and toxicity in plants.
Keywords: Chelant-Sepharose; Copper-binding protein; Immobilized metal affinity chromatography (IMAC); Copper stress; Removal of metal ions
Antioxidative role of selenoprotein W in oxidant-induced chicken splenic lymphocyte death by Dong Yu; Zi-wei Zhang; Hai-dong Yao; Shu Li; Shi-wen Xu (277-291).
To verify the antioxidative role of SelW in oxidant-induced chicken splenic lymphocyte, in this report, the influence of selenite supplementation and SelW gene silence on H2O2-mediated cell viability and cell apoptosis in cultured splenic lymphocyte derived from spleen of chicken were examined. The cultured cells were treated with sodium selenite and H2O2, or knocked down SelW with small interfering RNAs (siRNAs). The lymphocytes were examined for cell viability, cell apoptosis and mRNA expression levels of SelW and apoptosis-related genes (Bcl-2, Bax, Bak-1, caspase-3 and p53). The results show that the mRNA expression of SelW were effectively increased after treatment with sodium selenite, and H2O2-induced cell apoptosis was significantly decreased and cell viability was significantly increased. 20 μM H2O2 was found to induce cell apoptosis and decrease cell viability, which was alleviated obviously when cells were pretreated with sodium selenite before exposure to 20 μM H2O2. Meanwhile, H2O2 induced a significantly up-regulation of the Bax/Bcl-2 ratio, Bax, Bak-1, caspase-3 and p53 and down-regulation of Bcl-2 (P < 0.05). When lymphocytes were pretreated with Se before treated with H2O2, the Bax/Bcl-2 ratio and mRNA expression of those genes were significantly decreased, and Bcl-2 was increased (P < 0.05). SelW siRNA-transfected cells were more sensitive to the oxidative stress induced by treatment of H2O2 than control cells. Silencing of the lymphocyte SelW gene decreased their cell viability, and increased their apoptosis rate and susceptibility to H2O2. Silencing of SelW significantly up-regulated the Bax/Bcl-2 ratio, Bax, Bak-1, caspase-3 and p53 and down-regulated Bcl-2 (P < 0.05). The present study demonstrates that SelW plays an important role in protection of splenic lymphocyte of birds from oxidative stress.
Keywords: Selenoprotein W; Small interfering RNAs; Apoptosis; Splenic lymphocyte; Chicken
Perinatal low-dose iron treatment influences susceptibility to diet-induced adipogenesis in early-aged male Wistar rats by Alexey A. Tinkov; Elizaveta V. Popova; Valentina S. Polyakova; Alexandr A. Nikonorov (293-303).
The primary objective of the study was to estimate the effect of perinatal low-dose iron supplementation on diet-induced adipogenic action of a high-fat diet in the male offspring. The experimental group of pregnant dams was treated with drinking water containing 3 mg/l ferrous sulfate (FeSO4·7H2O) from the 2nd week of pregnancy till the end of lactation (the 21st day postpartum). The control group of dams obtained pure drinking water. The obtained male littermates were fed standard and high-fat diets (HFD) for 1 month. Animals’ morphometric parameters as well as serum lipoprotein profile, glucose, insulin, adipokines and cytokines concentrations were estimated. Adipose tissue oxidative stress biomarkers were also measured. It is shown that HFD-fed perinatally iron treated rats had a significantly higher adipose tissue mass in comparison with HFD-control ones. The experimental iron-treated males were also characterized by increased serum glucose and insulin concentrations. Perinatally iron treated HFD-fed animals’ leptin and proinflammatory cytokines concentrations exceeded the HFD-control values. Significant accumulation of free radical oxidation biomarkers is observed in adipose tissue samples. The lipoprotein spectra indicated initial atherogenic changes in the rats’ serum. Taken together, the study suggests that iron takes part in the developmental programming of adipogenesis.
Keywords: Iron; High-fat diet; Adiposity; Perinatal treatment; Insulin resistance; Inflammation
Cytoprotective mechanisms in rats lung parenchyma with zinc deprivation by Verónica S. Biaggio; Daiana G. Alvarez-Olmedo; María V. Perez Chaca; Natalia R. Salvetti; Susana R. Valdez; Mariel A. Fanelli; Hugo H. Ortega; Nidia N. Gomez; María S. Gimenez (305-315).
Suboptimal intake of Zinc (Zn) is one of the most common worldwide nutritional problems. The aim of this study is to provide new evidence on the relation between moderate Zn restriction, and cytoprotective functions in airway epithelium. We analyzed the effect of moderate Zn deficiency (ZD) on the expression of several pro and anti-apoptotic proteins and cytoprotective factors (Hsp27 and Hsp 70i), as well as the effect of restoring Zn during the refeeding period. Adult male rats were divided into three groups: Zn-adequate control group, Zn-deficient group and Zn-refed group. Our previous findings showed an important oxidative and nitrosative stress during ZD, this situation is accompanied by inflammation and alterations in the expression of matrix extracellular proteins. We observed a strong immunopositive area of anti and pro-apoptotics proteins in ZD groups. The mRNA levels of Nrf-2, Bax and Bad were increased in ZD, while in ZD refed group its levels were similar to the control values. The increased expression of Nrf-2 is likely to be critical for protection of lung under inflammatory process triggered during ZD. Hsp27 and Hsp 70i showed an increase of immunostaining area but they were not significant. During the supplementation period, heat-shock proteins increased significantly. In conclusion, our results provide further evidence of the pathways involved in cytoprotection and apoptosis caused by ZD. Additional studies are required in order to investigate whether Hsp27 and Hsp70 are consistently associated with cellular stress and inflammation in lung. There may be a beneficial role for improved Zn nutrition or Zn supplements early in lung pathology.
Keywords: Cytoprotective mechanism; Zn deficiency; Lung
Acute and long-term effects of arsenite in HepG2 cells: modulation of insulin signaling by Ingrit Hamann; Kerstin Petroll; Xiaoqing Hou; Anwar Anwar-Mohamed; Ayman O. S. El-Kadi; Lars-Oliver Klotz (317-332).
Epidemiological studies have indicated a relationship between the prevalence of diabetes and exposure to arsenic. Mechanisms by which arsenic may cause this diabetogenic effect are largely unknown. The phosphoinositide 3′-kinase (PI3K)/Akt signaling pathway plays an important role in insulin signaling by controlling glucose metabolism, in part through regulating the activity of FoxO transcription factors. The present study aimed at investigating the effect of short and long-term exposure to arsenite on insulin signaling in HepG2 human hepatoma cells, the role of PI3K/Akt signaling therein and the modulation of target genes controlled by insulin. Exposure of cells to arsenite for 24 h rendered cells less responsive toward stimulation of Akt by insulin. At the same time, short-term exposure to arsenite induced a concentration-dependent increase in phosphorylation of Akt at Ser-473, followed by phosphorylation of FoxO proteins at sites known to be phosphorylated by Akt. Phosphorylation of FoxOs was prevented by wortmannin, pointing to the involvement of PI3K. Arsenite exposure resulted in attenuation of FoxO DNA binding and in nuclear exclusion of FoxO1a-EGFP. A 24-h exposure of HepG2 cells to submicromolar concentrations of arsenite resulted in downregulation of glucose 6-phosphatase (G6Pase) and selenoprotein P (SelP) mRNA levels. Curiously, arsenite had a dual effect on SelP protein levels, inducing a small increase in the nanomolar and a distinct decrease in the micromolar concentration range. Interestingly, arsenite-induced long-term effects on G6Pase and SelP mRNA or SelP protein levels were not blocked by the PI3K inhibitor, wortmannin. In conclusion, arsenite perturbs cellular signaling pathways involved in fuel metabolism: it impairs cellular responsiveness toward insulin, while at the same time stimulating insulin-like signaling to attenuate the expression of genes involved in glucose metabolism and the release of the hepatokine SelP, which is known to modulate peripheral insulin sensitivity.
Keywords: Insulin signaling; FoxO transcription factors; Arsenic; Akt; HepG2 cells; Selenium homeostasis
Relations of the Al, B, Ba, Br, Ca, Cl, Cu, Fe, K, Li, Mg, Mn, Na, P, S, Si, Sr, and Zn mass fractions to morphometric parameters in pediatric and nonhyperplastic young adult prostate glands by Vladimir Zaichick; Sofia Zaichick (333-348).
The variation with age of the 18 trace element mass fractions and some histological characteristics of intact prostate glands of 50 subjects aged 0–30 years was investigated by instrumental neutron activation analysis, inductively coupled plasma atomic emission spectrometry, and a quantitative morphometric analysis. Mean values ± standard error of the mean (M ± SΕΜ) for the mass fractions (in milligrams per kilogram wet tissue) of these trace elements in pre-puberty were: Al 28.5 ± 9.0, B 0.40 ± 0.11, Ba 1.48 ± 0.44, Br 10.5 ± 1.5, Ca 241 ± 30, Cl 3,203 ± 278, Cu 3.51 ± 0.89, Fe 33.7 ± 4.1, K 2,364 ± 145, Li 0.020 ± 0.004, Mg 153 ± 23, Mn 0.46 ± 0.06, Na 2,286 ± 130, P 1,391 ± 100, S 1,698 ± 132, Si 62 ± 11, Sr 0.38 ± 0.08, and Zn 27.6 ± 2.3. During puberty and postpuberty, when there is a significant increase in circulating androgens, the mean values were: Al 7.2 ± 1.4, B 0.21 ± 0.05, Ba 0.25 ± 0.06, Br 5.8 ± 1.0, Ca 433 ± 81, Cl 2,314 ± 201, Cu 1.77 ± 0.13, Fe 20.9 ± 1.6, K 2,585 ± 118, Li 0.0088 ± 0.0014, Mg 232 ± 27, Mn 0.34 ± 0.04, Na 1,875 ± 107, P 1,403 ± 98, S 1,673 ± 73, Si 22.2 ± 3.1, Sr 0.22 ± 0.03, and Zn 93.3 ± 8.9. Mean values (M ± SΕΜ) of percent volumes (%) of the stroma, epithelium and lumen in the prostate before puberty were 73.4 ± 2.6, 20.4 ± 1.7, and 4.45 ± 0.94, respectively, versus 46.5 ± 2.5, 38.5 ± 1.9, and 14.9 ± 1.2 during puberty and postpuberty. This work’s results confirm that the Zn mass fraction in prostate tissue is an androgen-dependent parameter. For the first time it has been demonstrated that the glandular lumen is a main pool of Ca, Mg, and Zn accumulation and that the stroma is a main pool of Al, B, Ba, Br, Cl, Cu, Fe, Mn, Na, and Si accumulation in the normal human prostate, for the age range 0–30 years. It was concluded that the Ca, Mg, and Zn binds tightly within the prostatic fluid, because the volume of glandular lumen reflects the volume of prostatic fluid.
Keywords: Trace elements; Quantitative morphometry; Pediatric and nonhyperplastic young adult prostate gland; INAA; ICP-AES; Age-related changes; Correlations between histologic parameters and trace element mass fractions
Iron toxicity mediated by oxidative stress enhances tissue damage in an animal model of diabetes by Ana Flávia S. Sampaio; Maisa Silva; Waleska C. Dornas; Daniela C. Costa; Marcelo E. Silva; Rinaldo C. dos Santos; Wanderson G. de Lima; Maria Lúcia Pedrosa (349-361).
Although iron is a first-line pro-oxidant that modulates clinical manifestations of various systemic diseases, including diabetes, the individual tissue damage generated by active oxidant insults has not been demonstrated in current animal models of diabetes. We tested the hypothesis that oxidative stress is involved in the severity of the tissues injury when iron supplementation is administered in a model of type 1 diabetes. Streptozotocin (Stz)-induced diabetic and non-diabetic Fischer rats were maintained with or without a treatment consisting of iron dextran ip at 0.1 mL day−1 doses administered for 4 days at intervals of 5 days. After 3 weeks, an extensive increase (p < 0.001) in the production of reactive oxygen species (ROS) in neutrophils of the diabetic animals on iron overload was observed. Histological analysis revealed that this treatment also resulted in higher (p < 0.05) tissue iron deposits, a higher (p < 0.001) number of inflammatory cells in the pancreas, and apparent cardiac fibrosis, as shown by an increase (p < 0.05) in type III collagen levels, which result in dysfunctional myocardial. Carbonyl protein modification, a marker of oxidative stress, was consistently higher (p < 0.01) in the tissues of the iron-treated rats with diabetes. Moreover, a significant positive correlation was found between ROS production and iron pancreas stores (r = 0.42, p < 0.04), iron heart stores (r = 0.54, p < 0.04), and change of the carbonyl protein content in pancreas (r = 0.49, p < 0.009), and heart (r = 0.48, p < 0.02). A negative correlation was still found between ROS production and total glutathione content in pancreas (r = −0.50, p < 0.03) and heart (r = −0.45, p < 0.04). In conclusion, our results suggest that amplified toxicity in pancreatic and cardiac tissues in rats with diabetes on iron overload might be attributed to increased oxidative stress.
Keywords: Diabetes; Heart; Iron; Pancreas; Reactive oxygen species
Phosphate relieves chromium toxicity in Arabidopsis thaliana plants by interfering with chromate uptake by José López-Bucio; Fátima Hernández-Madrigal; Carlos Cervantes; Randy Ortiz-Castro; Yazmín Carreón-Abud; Miguel Martínez-Trujillo (363-370).
Soil contamination by hexavalent chromium [Cr(VI) or chromate] due to anthropogenic activities has become an increasingly important environmental problem. Mineral nutrients such as phosphate (Pi), sulfate and nitrate have been reported to attenuate Cr(VI) toxicity, but the underlying mechanisms remain to be clarified. Here, we show that chromate activates the expression of low-Pi inducible reporter genes AtPT1 and AtPT2 in Arabidopsis thaliana transgenic seedlings. Primary-root growth was inhibited by 60 % in AtPT2::uidA-expressing seedlings upon exposure to 140-μM Cr(VI). However, increasing the Pi and sulfate supply to the seedlings that were experiencing Cr(VI) toxicity completely and partially restored the root growth, respectively. This effect correlated with the Cr(VI)-induced AtPT2::uidA expression being completely reversed by addition of Pi. To evaluate whether the nutrient supply may affect the endogenous level of Cr in plants grown under toxic Cr(VI) levels, the contents of Cr were measured (by ICP-MS analyses) in seedlings treated with Cr and with or without Pi, sulfate or nitrate. It was found that Cr accumulation increases tenfold in plants treated with 140-μM Cr(VI) without modifying the phosphorus concentration in the plant. In contrast, the supply of Pi specifically decreased the Cr content to levels similar to those found in seedlings grown in medium without chromate. Taken together, these results show that in A. thaliana seedlings the uptake of Cr(VI) is reduced by Pi. Moreover, our data indicate that Pi and sulfate supplements may be useful in strategies for handling Cr-contaminated soils.
Keywords: Arabidopsis thaliana ; Chromate; Phosphate; Sulfate; Root development; Metal uptake
Heavy metals toxicity: effect of cadmium ions on amyloid beta protein 1–42. Possible implications for Alzheimer’s disease by Gabriella Notarachille; Fabio Arnesano; Vincenza Calò; Daniela Meleleo (371-388).
Cadmium (Cd) is an environmental contaminant, highly toxic to humans. This biologically non-essential element accumulates in the body, especially in the kidney, liver, lung and brain and can induce several toxic effects, depending on the concentration and the exposure time. Cd has been linked to Alzheimer’s disease (AD) as a probable risk factor, as it shows higher concentrations in brain tissues of AD patients than in healthy people, its implication in the formation of neurofibrillary tangles and in the aggregation process of amyloid beta peptides (AβPs). AβPs seem to have toxic properties, particularly in their aggregated state; insoluble AβP forms, such as small and large aggregates, protofibrils and fibrils, appear to be implicated in the pathogenesis of AD. In our study, we have evaluated the effect of Cd, at different concentrations, both on the AβP1–42 ion channel incorporated in a planar lipid membrane made up of phosphatidylcholine containing 30 % cholesterol and on the secondary structure of AβP1–42 in aqueous environment. Cadmium is able to interact with the AβP1–42 peptide by acting on the channel incorporated into the membrane as well as on the peptide in solution, both decreasing AβP1–42 channel frequency and in solution forming large and amorphous aggregates prone to precipitate. These experimental observations suggesting a toxic role for Cd strengthen the hypothesis that Cd may interact directly with AβPs and may be a risk factor in AD.
Keywords: Cadmium; AβP; Aggregation; Ion channel; Membranes
Photosynthetic responses of Oryza sativa L. seedlings to cadmium stress: physiological, biochemical and ultrastructural analyses by Yuwen Wang; Xiaohan Jiang; Kang Li; Min Wu; Rufeng Zhang; Lu Zhang; Guoxiang Chen (389-401).
In the present study, photosynthetic responses induced by cadmium stress in chlorophyll biosynthesis, photochemical activities, the stability of thylakoid membranes chlorophyll-protein complexes and the chloroplast ultrastructure of the cereal crop Oryza sativa L. were characterized. Cadmium inhibited the biosynthesis of chlorophyll by interfering with activity of δ-aminolevulinic acid dehydratase in the rice seedlings. For the photochemical activities analyses, the extent of the decrease in photosystem II activity was much greater than that in the PS I activity. The variations in the chlorophyll a fluorescence parameters also indicated that cadmium toxicity drastically affected the photochemistry of PS II. Biochemical analyses by BN-PAGE and protein immunoblot showed that cadmium toxicity considerably affected the stability of PS II-core, cytb 6 /f, RuBisCO, PSI + LHCI and LHCII (Trimeric). We observed the rate of the thylakoid membranes protein degradation, was mainly at the level of RbcL, PsaA, Lhca1 and D1. In addition, the damages to chloroplast structure and thylakoid stacking analyzed by transmission electron microscopy were indicative of general disarray in the photosynthetic functions exerted by cadmium toxicity. These results are valuable for understanding the biological consequences of heavy metals contamination particularly in soils devoted to organic agriculture.
Keywords: Photosynthetic responses; Cadmium; Chlorophyll-protein complexes
Determination of ionophore antibiotics nactins produced by fecal Streptomyces from sheep by Jun Wang; Hongming Tan; Yu Lu; Lixiang Cao (403-407).
To investigate the correlation between fecal actinobacteria and host animals, Streptomyces was isolated from fresh faeces of healthy sheep and secondary metabolites were analyzed. The most frequently isolated strain S161 with antibiotic activity against bacteria and fungi were analyzed. The S161 showed the highest 99 % similarity to Streptomyces canus DSB17 based on the 16S rRNA gene sequence analysis. Metabolite analysis based on MS and NMR spectra showed that S161 produces nactins, cyclotetralactones derived from nonactic acid and homononactic acid as building units of ionophoretic character. Due to ionophores are antimicrobial compounds that are commonly fed to ruminant animals to improve feed efficiency, stable beneficial interactions between Streptomyces bacteria and vertebrates have been demonstrated.
Keywords: Ionophores; Nactins; Ruminant; Streptomyces