Profiling of selected indigenous rice (Oryza sativa L.) landraces of Rarh Bengal in relation to osmotic stress tolerance

A total of ten rare indigenous rice landraces of West Bengal were screened for germination potential and seedling growth under varying concentrations of sodium chloride (NaCl) and polyethylene glycol (PEG) solutions as osmotic stress inducing agents. Among the studied rice landraces Kelas and Bhut Moori showed highest degree of tolerance to induced osmotic stresses. Proline content of the studied lines was also determined. Genetic relationship among the studied rice landraces was assessed with 22 previously reported osmotic stress tolerance linked Simple Sequence Repeat (SSR) markers. The identified allelic variants in form of amplified products size (molecular weight) for each SSR marker were documented to find out allele mining set for the linked markers of the studied genotypes in relation to osmotic stress tolerance. A Microsatellite Panel was constructed for the different allelic forms (size of amplified products) of each used marker. Among 22 SSR markers, ten showed unique alleles in form of single specific amplified product for the studied four genotypes which can be used for varietal identification. Genetic relationship among the studied rice lines was determined and a dendrogram was constructed to reveal their genetic inter-relationship. Polymorphism Information Content (PIC) for each used marker was also calculated for the studied rice lines.     

Cadmium causes the oxidative modification of proteins in pea plants

In pea (Pisum sativum L.) leaves from plants grown in the presence of 50 µm CdCl₂ the oxidative production of carbonyl groups in proteins, the rate of protein degradation and the proteolytic activity were investigated. In leaf extracts the content of carbonyl groups measured by derivatization with 2,4‐dinitrophenylhydrazine (DNPH), was two‐fold higher in plants treated with Cd than in control plants. The identification of oxidized proteins was carried out by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis of proteins derivatized with DNPH and immunochemical detection with an antibody against DNPH. The intensity of the reactive bands was higher in plants exposed to Cd than in controls. By using different antibodies some of the oxidized proteins were identified as Rubisco, glutathione reductase, manganese superoxide dismutase, and catalase. The incubation of leaf crude extracts with increasing H₂O₂ concentrations showed a progressive enhancement in carbonyl content and the pattern of oxidized proteins was similar to that found in Cd‐treated plants. Oxidized proteins were more efficiently degraded, and the proteolytic activity increased 20% due to the metal treatment. In peroxisomes purified from pea leaves a rise in the carbonyl content similar to that obtained in crude extracts from Cd‐treated plants was observed, but the functionality of the peroxisomal membrane was not apparently affected by Cd. Results obtained demonstrate the participation of both oxidative stress, probably mediated by H₂O₂, and proteolytic degradation in the mechanism of Cd toxicity in leaves of pea plants, and they appear to be involved in the Cd‐induced senescence previously reported in these plants.     

Arabidopsis casein kinase 1-like 8 enhances NaCl tolerance,early flowering,and the expression of flowering-related genes

Members of the casein kinase 1 (CK1) family are evolutionarily conserved eukaryotic protein kinases involved in various cellular, physiological, and developmental processes in yeast. However, the biological roles of CK1 members in plants are poorly understood. Here, we report that an Arabidopsis CK1 member named casein kinase 1-like 8 (CKL8) was ubiquitously expressed in all plant organs, mainly in the stems of seedlings according to quantitative real-time PCR. Western blotting showed a remarkable expression of the AtCKL8 gene in transgenic plants induced by high salinity. A histochemical assay of AtCKL8 promoter::GUS expression revealed that the AtCKL8 promoter is very active in both seedlings and adult plants subjected to the salinity stress, while no GUS activity was detectable in all the transgenic plants grown under normal conditions. In a subcellular distribution analysis, the AtCKL8-GFP fusion protein was localized mainly in the cell membrane. AtCKL8-overexpressing transgenic plants showed an insensitivity to high salinity and an early flowering phenotype. Overall, these findings suggest that AtCKL8 plays a positive role in NaCl signaling and improves salt stress tolerance in transgenic Arabidopsis.     

Hyperbaric oxygne tolerance in newborn mammals-hypothesis on mechanisms and outcome

Newborn mammals, compared to adults, are extremely resistant to the CNS effects of hyperbaric oxygenation (HBO) induced by excessive generation of reactive oxygen species. This tolerance to HBO may be related to either physiological responses or the chemical characteristics of the immature brain, including a low cerebral blood flow and energy metabolism and a low concentration of polyunsaturated fatty acids. In adult mammals the main protective mechanism against CNS oxygen toxicity, besides endogenous antioxidants, is a transient HBO-induced cerebral vasoconstriction. How cerebral vasculature reacts to HBO in the immature brain is not known. We present indirect evidence suggesting that HBO in newborn rats induces a persistent cerebral vasoconstriction concurrently with a severe and maintained reduction in ventilation. It is speculated that the outcome of these physiologic responses to hyperoxic exposures may be: (a) extension of tolerance to both CNS and pulmonary oxygen poisoning; (b) creation of a profound hypoxic-ischemic condition in vulnerable neural structures: and (c) impairement of the circulatory and ventilatory responses to hypoxic stimuli on return to air consequent development of a secondary hypoxic-ischemic condition. These hypothetical pre- and post-HBO events may set the stage for the development of some delayed neurological disorders, including the retinopathy of prematurity and the retardation of brain development in fetuses or prematurely-born infants subjected to oxygen therapy.     

NOX4-dependent Hydrogen peroxide promotes shear stress-induced SHP2 sulfenylation and eNOS activation

Laminar shear stress (LSS) triggers signals that ultimately result in atheroprotection and vasodilatation. Early responses are related to the activation of specific signaling cascades. We investigated the participation of redox-mediated modifications and in particular the role of hydrogen peroxide (H₂O₂) in the sulfenylation of redox-sensitive phosphatases. Exposure of vascular endothelial cells to short periods of LSS (12 dyn/cm²) resulted in the generation of superoxide radical anion as detected by the formation of 2-hydroxyethidium by HPLC and its subsequent conversion to H₂O₂, which was corroborated by the increase in the fluorescence of the specific peroxide sensor HyPer. By using biotinylated dimedone we detected increased total protein sulfenylation in the bovine proteome, which was dependent on NADPH oxidase 4 (NOX4)-mediated generation of peroxide. Mass spectrometry analysis allowed us to identify the phosphatase SHP2 as a protein susceptible to sulfenylation under LSS. Given the dependence of FAK activity on SHP2 function, we explored the role of FAK under LSS conditions. FAK activation and subsequent endothelial NO synthase (eNOS) phosphorylation were promoted by LSS and both processes were dependent on NOX4, as demonstrated in lung endothelial cells isolated from NOX4-null mice. These results support the idea that LSS elicits redox-sensitive signal transduction responses involving NOX4-dependent generation of hydrogen peroxide, SHP2 sulfenylation, and ulterior FAK-mediated eNOS activation.     

Monoamine oxidase-A is an important source of oxidative stress and promotes cardiac dysfunction,apoptosis, and fibrosis in diabetic cardiomyopathy

Oxidative stress is closely associated with the pathophysiology of diabetic cardiomyopathy (DCM). The mitochondrial flavoenzyme monoamine oxidase A (MAO-A) is an important source of oxidative stress in the myocardium. We sought to determine whether MAO-A plays a major role in modulating DCM. Diabetes was induced in Wistar rats by single intraperitoneal injection of streptozotocin (STZ). To investigate the role of MAO-A in the development of pathophysiological features of DCM, hyperglycemic and age-matched control rats were treated with or without the MAO-A-specific inhibitor clorgyline (CLG) at 1 mg/kg/day for 8 weeks. Diabetes upregulated MAO-A activity; elevated markers of oxidative stress such as cardiac lipid peroxidation, superoxide dismutase activity, and UCP3 protein expression; enhanced apoptotic cell death; and increased fibrosis. All these parameters were significantly attenuated by CLG treatment. In addition, treatment with CLG substantially prevented diabetes-induced cardiac contractile dysfunction as evidenced by decreased QRS, QT, and corrected QT intervals, measured by ECG, and LV systolic and LV end-diastolic pressure measured by microtip pressure transducer. These beneficial effects of CLG were seen despite the persistent hyperglycemic and hyperlipidemic environments in STZ-induced experimental diabetes. In summary, this study provides strong evidence that MAO-A is an important source of oxidative stress in the heart and that MAO-A-derived reactive oxygen species contribute to DCM.