Overexpression of the glutamine synthetase gene modulates oxidative stress response in rice after exposure to cadmium stress

Key message

Overexpression of OsGS gene modulates oxidative stress response in rice after exposure to cadmium stress. Our results describe the features of transformants with enhanced tolerance to Cd and abiotic stresses.

Abstract

Glutamine synthetase (GS) (EC 6.3.1.2) is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine. Exposure of plants to cadmium (Cd) has been reported to decrease GS activity in maize, pea, bean, and rice. To better understand the function of the GS gene under Cd stress in rice, we constructed a recombinant pART vector carrying the GS gene under the control of the CaMV 35S promoter and OCS terminator and transformed using Agrobacterium tumefaciens. We then investigated GS overexpressing rice lines at the physiological and molecular levels under Cd toxicity and abiotic stress conditions. We observed a decrease in GS enzyme activity and mRNA expression among transgenic and wild-type plants subjected to Cd stress. The decrease, however, was significantly lower in the wild type than in the transgenic plants. This was further validated by the high GS mRNA expression and enzyme activity in most of the transgenic lines. Moreover, after 10 days of exposure to Cd stress, increase in the glutamine reductase activity and low or no malondialdehyde contents were observed. These results showed that overexpression of the GS gene in rice modulated the expression of enzymes responsible for membrane peroxidation that may result in plant death.     

Establishment of a Captive All‐male Group of Proboscis Monkey (Nasalis larvatus) at the Singapore Zoo

Surplus male proboscis monkeys at the Singapore Zoo pose a considerable problem for maintenance and maximizing of exhibition potential. In 2008, a new exhibit was constructed to house and display a group of six proboscis monkey males born in Singapore Zoo. To document and monitor the all‐male group establishment in the new exhibit, we conducted observations on intragroup interactions between the monkeys, spatial use of their new exhibit, and visitor effects on their behavior. We found contact aggressive interactions between the monkeys to be consistently lower than noncontact aggressive interactions and by week six of introduction to the new exhibit, contact aggression was almost nonevident. Affiliative interactions also developed between individuals in the group, with an interface of aggressive and socioreconcilatory behavior influenced by food competition and a dominance hierarchy. This was evident from significantly higher overall aggression and affiliation during feeding times compared to nonfeeding times, and this was reduced when food competition was mitigated by modifying the feeding regime. We measured the groups’ spatial use of the exhibit and the relation to behavior, crowd size, and density. Our results showed that the proboscis monkeys utilized the available exhibit space, were largely unaffected by visitor crowd size and density, and were able to exhibit a variety of natural behaviors, including swimming. Our accomplishment in maintaining and displaying an all‐male group of proboscis monkeys in captivity provides viable options for more comprehensive captive management and breeding programs for this endangered species. Zoo Biol. 32:281‐290, 2013. © 2012 Wiley Periodicals, Inc.     

A Role for Ifit2 in Restricting West Nile Virus Infection in the Brain

Previous studies have demonstrated that type I interferon (IFN-I) restricts West Nile virus (WNV) replication and pathogenesis in peripheral and central nervous system (CNS) tissues. However, the in vivo role of specific antiviral genes that are induced by IFN-I against WNV infection remains less well characterized. Here, using Ifit2^−/− mice, we defined the antiviral function of the interferon-stimulated gene (ISG) Ifit2 in limiting infection and disease in vivo by a virulent North American strain of WNV. Compared to congenic wild-type controls, Ifit2^−/− mice showed enhanced WNV infection in a tissue-restricted manner, with preferential replication in the CNS of animals lacking Ifit2. Virological analysis of cultured macrophages, dendritic cells, fibroblasts, cerebellar granule cell neurons, and cortical neurons revealed cell type-specific antiviral functions of Ifit2 against WNV. In comparison, small effects of Ifit2 were observed on the induction or magnitude of innate or adaptive immune responses. Our results suggest that Ifit2 restricts WNV infection and pathogenesis in different tissues in a cell type-specific manner.     

Regional Differences in Elements of Human Peroneus LongusTendons

Many studies have been performed on the structure, molecular composition, and biochemical properties of tendons. However, comparatively little research has been conducted on the content of various trace elements within tendons. Six elements were analyzed in four regions of the peroneus longus tendon: the tensional part of the tendon immediately proximal to the lateral malleolus (region A), the compressive region of the tendon in contact with the lateral malleolus (region B), the compressive region of the tendon in contact with the deep surface of the cuboid (region C), and the tensional part of the tendon between the cuboid and first metatarsal, to which the tendon is attached (region D). Regions B and C are wraparound regions. The calcium content was higher in region C (2.10?±?0.93 mg/g) than in both regions A (1.25?±?0.51 mg/g) and D (1.43?±?0.41 mg/g) (p?<?0.05), indicating that it is likely related to regional differences in cartilage degeneration. The phosphorus content was also higher in region C, possibly because of low alkaline phosphatase activity in this region. The sulfur content was higher in the wraparound regions (region B: 0.98?±?0.09 mg/g, region C: 1.24?±?0.19 mg/g) than in both regions A (0.83?±?0.11 mg/g) and D (0.83?±?0.1 mg/g) (p?<?0.01); sulfur content is thought to be influenced by tendon–bone compression. Finally, the magnesium content in the wraparound regions was also higher, which is probably related to a higher level of fibrocartilage. No significant relationships were found with regard to zinc or iron. Overall, the findings of the present study indicate that element contents are related to function and anatomical differences in tendons, and that they may even vary within the same tendon.     

Regulation of Phospholipase D Activity and Phosphatidic Acid Production after Purinergic (P2Y6) Receptor Stimulation

Phosphatidic acid (PA) is a lipid second messenger located at the intersection of several lipid metabolism and cell signaling events including membrane trafficking, survival, and proliferation. Generation of signaling PA has long been primarily attributed to the activation of phospholipase D (PLD). PLD catalyzes the hydrolysis of phosphatidylcholine into PA. A variety of both receptor-tyrosine kinase and G-protein-coupled receptor stimulations have been shown to lead to PLD activation and PA generation. This study focuses on profiling the PA pool upon P2Y₆ receptor signaling manipulation to determine the major PA producing enzymes. Here we show that PLD, although highly active, is not responsible for the majority of stable PA being produced upon UDP stimulation of the P2Y₆ receptor and that PA levels are tightly regulated. By following PA flux in the cell we show that PLD is involved in an initial increase in PA upon receptor stimulation; however, when PLD is blocked, the cell compensates by increasing PA production from other sources. We further delineate the P2Y₆ signaling pathway showing that phospholipase Cβ3 (PLCβ3), PLCδ1, DGKζ and PLD are all downstream of receptor activation. We also show that DGKζ is a novel negative regulator of PLD activity in this system that occurs through an inhibitory mechanism with PKCα. These results further define the downstream events resulting in PA production in the P2Y₆ receptor signaling pathway.     

The Soluble Interleukin-6 Receptor Is a Mediator of Hematopoietic and Skeletal Actions of Parathyroid Hormone

Both PTH and IL-6 signaling play pivotal roles in hematopoiesis and skeletal biology, but their interdependence is unclear. The purpose of this study was to evaluate the effect of IL-6 and soluble IL-6 receptor (sIL-6R) on hematopoietic and skeletal actions of PTH. In the bone microenvironment, PTH stimulated sIL-6R protein levels in primary osteoblast cultures in vitro and bone marrow in vivo in both IL-6^+/+ and IL-6^−/− mice. PTH-mediated hematopoietic cell expansion was attenuated in IL-6^−/− compared with IL-6^+/+ bone marrow, whereas sIL-6R treatment amplified PTH actions in IL-6^−/− earlier than IL-6^+/+ marrow cultures. Blocking sIL-6R signaling with sgp130 (soluble glycoprotein 130 receptor) inhibited PTH-dependent hematopoietic cell expansion in IL-6^−/− marrow. In the skeletal system, although intermittent PTH administration to IL-6^+/+ and IL-6^−/− mice resulted in similar anabolic actions, blocking sIL-6R significantly attenuated PTH anabolic actions. sIL-6R showed no direct effects on osteoblast proliferation or differentiation in vitro; however, it up-regulated myeloid cell expansion and production of the mesenchymal stem cell recruiting agent, TGF-β1 in the bone marrow microenvironment. Collectively, sIL-6R demonstrated orphan function and mediated PTH anabolic actions in bone in association with support of myeloid lineage cells in the hematopoietic system.     

Combinatorial biosynthesis and antibacterial evaluation of glycosylated derivatives of 12-membered macrolide antibiotic YC-17

Expression plasmids carrying different deoxysugar biosynthetic gene cassettes and the gene encoding a substrate-flexible glycosyltransferase DesVII were constructed and introduced into Streptomyces venezuelae YJ003 mutant strain bearing a deletion of a desosamine biosynthetic (des) gene cluster. The resulting recombinants produced macrolide antibiotic YC-17 analogs possessing unnatural sugars replacing native d-desosamine. These metabolites were isolated and further purified using chromatographic techniques and their structures were determined as d-quinovosyl-10-deoxymethynolide, l-rhamnosyl-10-deoxymethynolide, l-olivosyl-10-deoxymethynolide, and d-boivinosyl-10-deoxymethynolide on the basis of 1D and 2D NMR and MS analyses and the stereochemistry of sugars was confirmed using coupling constant values and NOE correlations. Their antibacterial activities were evaluated in vitro against erythromycin-susceptible and -resistant Enterococcus faecium and Staphylococcus aureus. Substitution with l-rhamnose displayed better antibacterial activity than parent compound YC-17 containing native sugar d-desosamine. The present study on relationships between chemical structures and antibacterial activities could be useful in generation of novel advanced antibiotics utilizing combinatorial biosynthesis approach.