Oligogalacturonides stimulate antioxidant system in alfalfa roots

Alfalfa (Medicago sativa L.) roots were treated with 50 and 100 μg cm⁻³ of oligogalacturonide (OGA) solutions with a degree of polymerization between 7 and 15. Changes in the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) as well as ascorbate (ASC) content were determined in crude extract of alfalfa roots after 30, 60 and 120 min of treatment. An increase in the SOD activity was observed in roots treated with 50 and 100 μg cm⁻³ OGA, which could be related to its O₂ ^·− scavenging function. As concern H₂O₂ scavenging, CAT activity was increased in the first 30 min by both OGA concentrations, while POX was a key enzyme at higher OGA concentration and treatment duration. ASC content firstly increased upon exposure to high OGA concentration, and then decreased after longer treatment while low OGA concentration had no effect on ASC content.     

Understanding the mechanisms of chilling injury in bell pepper fruits using the proteomic approach

In order to advance in the understanding of CI in pepper fruits, the cell ultrastructure alterations induced by CI and the physiological and metabolic changes have been studied along with the proteomic study. When stored at low temperatures bell pepper (Capsicum annuum) fruits exhibited visual CI symptoms and important alterations within the cell ultrastructure, since peroxisomes and starch grains were not detected and the structure of the chloroplast was seriously damaged in chilled tissues. Physiological and metabolic disorders were also observed in chilled fruits, such as higher ethylene production, increased MDA content, changes in sugar and organic acids and enzymatic activities. The comparative proteomic analysis between control and chilled fruits reveals that the main alterations induced by CI in bell pepper fruits are linked to redox homeostasis and carbohydrate metabolism. Thus, protein abundance in the ascorbate-glutathione cycle is altered and catalase is down-regulated. Key proteins from glycolysis, Calvin cycle and Krebs cycle are also inhibited in chilled fruits. Enolase and GAPDH are revealed as proteins that may play a key role in the development of chilling injury. This study also provides the first evidence at the protein level that cytosolic MDH is involved in abiotic stress.     

Cysteine proteinases regulate chloroplast protein content and composition in tobacco leaves: a model for dynamic interactions with ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) vesicular bodies

The roles of cysteine proteinases (CP) in leaf protein accumulation and composition were investigated in transgenic tobacco (Nicotiana tabacum L.) plants expressing the rice cystatin, OC-1. The OC-1 protein was present in the cytosol, chloroplasts, and vacuole of the leaves of OC-1 expressing (OCE) plants. Changes in leaf protein composition and turnover caused by OC-1-dependent inhibition of CP activity were assessed in 8-week-old plants using proteomic analysis. Seven hundred and sixty-five soluble proteins were detected in the controls compared to 860 proteins in the OCE leaves. A cyclophilin, a histone, a peptidyl-prolyl cis-trans isomerase, and two ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activase isoforms were markedly altered in abundance in the OCE leaves. The senescence-related decline in photosynthesis and Rubisco activity was delayed in the OCE leaves. Similarly, OCE leaves maintained higher leaf Rubisco activities and protein than controls following dark chilling. Immunogold labelling studies with specific antibodies showed that Rubisco was present in Rubisco vesicular bodies (RVB) as well as in the chloroplasts of leaves from 8-week-old control and OCE plants. Western blot analysis of plants at 14 weeks after both genotypes had flowered revealed large increases in the amount of Rubisco protein in the OCE leaves compared to controls. These results demonstrate that CPs are involved in Rubisco turnover in leaves under optimal and stress conditions and that extra-plastidic RVB bodies are present even in young source leaves. Furthermore, these data form the basis for a new model of Rubisco protein turnover involving CPs and RVBs.     

A novel liver specific isoform of the rat LAR transcript is expressed as a truncated isoform encoded from a 5'UTR located within intron 11

Background  

The leukocyte common antigen related receptor (LAR) protein has been shown to modulate the signal transduction of a number of different growth factors, including insulin and insulin-like growth factor 1. Splice variants exhibit differing roles and are expressed according to tissue type and developmental stage.     

Enterococcal surface protein Esp is not essential for cell adhesion and intestinal colonization of Enterococcus faecium in mice

Background  

Enterococcus faecium has globally emerged as a cause of hospital-acquired infections with high colonization rates in hospitalized patients. The enterococcal surface protein Esp, identified as a potential virulence factor, is specifically linked to nosocomial clonal lineages that are genetically distinct from indigenous E. faecium strains. To investigate whether Esp facilitates bacterial adherence and intestinal colonization of E. faecium, we used human colorectal adenocarcinoma cells (Caco-2 cells) and an experimental colonization model in mice.     

Isoprenylhydroquinone glucoside: a new non-antioxidant inhibitor of peroxynitrite-mediated tyrosine nitration.

Three hydroquinone glucosides and four caffeoylquinic esters were examined for their effect on tyrosine nitration, as well as on the oxidation of dihydrorhodamine (DHR) 123 and cytochrome c(2+) induced by peroxynitrite. All these phenolics, which had previously been characterized as the active principles of the plant Phagnalon rupestre, were fairly active in preventing the oxidation of DHR 123, though inefficient in the cytochrome c test. While their antioxidant potency is associated with the presence of a caffeoyl moiety, not so an obvious chemical character was correlated to a greater activity against nitration of tyrosine. Here, the highest potency corresponded to 2-isoprenylhydroquinone-1-glucoside. On the basis of the fact that the susceptibility to nitration of given aromatic compound confers to it inhibitory activity of tyrosine nitration, the analysis of ultraviolet and nuclear magnetic resonance spectral shifts provides valuable information for explaining the ability of natural phenolics to interfere with that reaction.     

Oxidative stress induced by long-term plum pox virus infection in peach (Prunus persica)

In this study, the effect of long-term plum pox virus (PPV) infection on the response of certain antioxidant enzymes at the subcellular level was studied in peach plants ( Prunus persica (L.) Batch) (cv. GF305), which are characterized by great susceptibility to the virus. In infected plants, a decrease in the efficiency of excitation energy capture by PSII ( F _v'/ F _m') was observed, which was accompanied by a decrease in non-photochemical quenching (NPQ). p -Hydroxy-mercury benzoic acid (pHMB)-insensitive ascorbate peroxidase (APX) activity (class III peroxidase) was detected in both chloroplast and soluble fractions. In soluble fractions from inoculated peaches, a significant increase in pHMB-sensitive APX activity and a significant decrease in superoxide dismutase (SOD) activity were observed. These changes were correlated with the observations in isolated chloroplasts, where an increase in both pHMB-sensitive and pHMB-insensitive APX activities was observed, whereas significant decreases in SOD, monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) activities were produced. According to these results, as a consequence of PPV infection, an oxidative stress, indicated by an increase in lipid peroxidation and protein oxidation, was produced in peach leaves, which was monitored by the diaminobenzidine (DAB) peroxidase-coupled H₂O₂ probe. PPV infection produced an alteration in chloroplast ultrastructure, giving rise to dilated thylakoid membranes. PPV-infected peach leaves showed a decreased amount of starch in chloroplasts from palisade parenchyma, as well as an increase in the number and size of plastoglobuli, in relation to control plants. The results suggest that long-term PPV infection produces an oxidative stress, and that an antioxidative metabolism imbalance may be related to the progress of PPV infection and symptoms in peach plants.     

Genetic analysis of variation in micropropagated plants of Melia azedarach L.

Summary Plants were regenerated by shoot multiplication from four clones of Melia azedarach L. during 12 mo. of subculturing. One hundred and one of these plants were examined by randomly amplified polymorphic DNA analysis. All regenerated plants showed at least one polymorphism. However, no chromosome number alterations were observed. The pattern of variation obtained by principal coordinated analysis showed a random distribution of variation among regenerated plants and their controls, indicating that genetic alterations were not cumulative during in vitro culture. Similar results were found using Shannon's index, which revealed that 50% of the observed diversity resided among plants coming from the same subculture generation. This high intraclonal variation does not provide a clear scenario for predicting the amount of culture time required to preserve genetic fidelity in commercially micropropagated M. azedarach plants. Our work suggests that other mechanisms, such as chimerism, contribute to intraclonal heterogeneity in vitro.