Identification of a hydrogen peroxide signalling pathway in the control of light-dependent germination in Arabidopsis.

Germination is controlled by external factors, such as temperature, water, light and by hormone balance. Recently, reactive oxygen species (ROS) have been shown to act as messengers during plant development, stress responses and programmed cell death. We analyzed the role of ROS during germination and demonstrated that ROS in addition to their role as cell wall loosening factor are essential signalling molecules in this process.

An anionic class III peroxidase from zucchini may regulate hypocotyl elongation through its auxin oxidase activity.

The high number of peroxidase genes explains the description of numerous physiological functions and the fact that the in planta function of a single isoform has never been characterized yet. We analyzed in transgenic Arabidopsis thaliana the localization of a zucchini isoperoxidase (APRX), previously purified thanks to its pectin binding ability. We confirmed that the protein is localized near the cell wall, mainly produced in the elongation area of the hypocotyls and respond to exogenous auxin.

Nox1 downstream of 12-lipoxygenase controls cell proliferation but not cell spreading of colon cancer cells.

The catalytic subunit of the NADPH oxidase complex, Nox1 (homologue of gp91phox/Nox2), expressed mainly in intestinal epithelial and vascular smooth muscle cells, functions in innate immune defense and cell proliferation. The molecular mechanisms underlying these functions, however, are not completely understood. We measured Nox1-dependent O2- production during cell spreading on Collagen IV (Coll IV) in colon carcinoma cell lines.

Nox1-dependent superoxide production controls colon adenocarcinoma cell migration.

Reactive oxygen species are well-known mediators of various biological responses. Recently, new homologues of the catalytic subunit of NADPH oxidase have been discovered in non-phagocytic cells. These new homologues (Nox1-Nox5) produce low levels of superoxides compared to the phagocytic homologue Nox2/gp91phox.

PPARalpha transcriptionally induces AhR expression in Caco-2, but represses AhR pro-inflammatory effects.

In this work we demonstrate that Caco-2 cell treatment with WY-14643 (a potent PPARalpha agonist) causes an increase in AhR expression. Luciferase assays and directed mutagenesis experiments showed that induction mainly occurred at transcriptional level and involved a PPRE site located within the AhR promoter. These results were further confirmed by the use of PPARalpha knockout mice in which AhR induction by WY14643 was abrogated.

Phylogenetic distribution of catalase-peroxidases: are there patches of order in chaos?

Hydrogen peroxide features in many biological oxidative processes and must be continuously degraded enzymatically either via a catalatic or a peroxidatic mechanism. For this purpose ancestral bacteria evolved a battery of different heme and non-heme enzymes, among which heme-containing catalase-peroxidases (CP) are one of the most widespread representatives. They are unique since they can follow both H(2)O(2)-degrading mechanisms, the catalase activity being clearly dominant.

PeroxiBase: the peroxidase database.

Peroxidases (EC 1.11.1.

Distribution of superoxide and hydrogen peroxide in Arabidopsis root and their influence on root development: possible interaction with peroxidases.

The respective distribution of superoxide (O(2) (.-)) and hydrogen peroxide (H(2)O(2)), two reactive oxygen species (ROS) involved in root growth and differentiation, was determined within the Arabidopsis root tip. We investigated the effect of changing the levels of these ROS on root development and the possible interactions with peroxidases.

Prokaryotic origins of the non-animal peroxidase superfamily and organelle-mediated transmission to eukaryotes.

Members of the superfamily of plant, fungal, and bacterial peroxidases are known to be present in a wide variety of living organisms. Extensive searching within sequencing projects identified organisms containing sequences of this superfamily. Class I peroxidases, cytochrome c peroxidase (CcP), ascorbate peroxidase (APx), and catalase peroxidase (CP), are known to be present in bacteria, fungi, and plants, but have now been found in various protists.

Localization of superoxide in the root apex of Arabidopsis.

Reactive oxygen species (ROS) fulfil many functions in plants. They have a signaling role in several physiological mechanisms, but they are also directly involved as substrates in important reactions, especially in the apoplast. Two ROS, superoxide and hydrogen peroxide, were shown to exhibit a typical accumulation pattern in the Arabidopsis root apex.

Integrin alphavbeta6 mediates HT29-D4 cell adhesion to MMP-processed fibrinogen in the presence of Mn2+.

Mn(2+) was found to induce adhesion of HT29-D4 adenoma carcinoma cells to fibrinogen (Fb). This was independent of the expression of the beta3 integrin subunit and involved endogenous alphavbeta6 but not alphavbeta5 integrin. Thus, addition of Mn(2+) led to a change in integrin alphavbeta6 specificity.

Morphological and physiological traits of three major Arabidopsis thaliana accessions.

Arabidopsis is currently the most studied organism in plant biology. Its short life cycle and small genome size have rendered it one of the principal model systems. Additionally, numerous large T-DNA insertion mutant collections are available.

PeroxiBase: a class III plant peroxidase database.

Class III plant peroxidases (EC 1.11.1.

Two cell wall associated peroxidases from Arabidopsis influence root elongation.

Two class III peroxidases from Arabidopsis, AtPrx33 and Atprx34, have been studied in this paper. Their encoding genes are mainly expressed in roots; AtPrx33 transcripts were also found in leaves and stems. Light activates the expression of both genes in seedlings.

Peroxidases have more functions than a Swiss army knife.

Plant peroxidases (class III peroxidases) are present in all land plants. They are members of a large multigenic family. Probably due to this high number of isoforms, and to a very heterogeneous regulation of their expression, plant peroxidases are involved in a broad range of physiological processes all along the plant life cycle.

Performing the paradoxical: how plant peroxidases modify the cell wall.

Since their appearance in the first land plants, genes encoding class III peroxidases have been duplicated many times during evolution and now compose a large multigene family. The reason for these many genes is elusive, and we are still searching for the specific function of every member of the family. Nevertheless, our current understanding implicates peroxidases as key players during the whole life cycle of a plant, and particularly in cell wall modifications, in roles that can be antagonistic depending on the developmental stage.

The class III peroxidase multigenic family in rice and its evolution in land plants.

Plant peroxidases (class III peroxidases, E.C. 1.

Expression analysis of the Arabidopsis peroxidase multigenic family.

Class III peroxidases form a numerous multigenic family in higher plants, whose expression is particularly sensitive to internal or external events. Arabidopsis thaliana genome harbours 73 genes encoding peroxidases. Since they exhibit homologies ranging from 28% to 93% at the nucleotide level, the risk of cross-hybridisation may be important when measuring the level of transcripts by blotting techniques, using whole cDNA sequences.

Cytokine-induced upregulation of NF-kappaB, IL-8, and ICAM-1 is dependent on colonic cell polarity: implication for PKCdelta.

As described for a long time, carcinoma-derived Caco-2 cells form a polarized epithelium in culture, whereas HT29-D4 cells are nonpolarized and undifferentiated but can form a polarized monolayer when cultured in a galactose-supplemented medium. Using NF-kappaB translocation and IL-8 and ICAM-1 gene activation as an index, we have studied the relationship between the differentiation state and the cell response to cytokines. We found that differentiated Caco-2 and HT29-D4 cells were responsive to both cytokines TNFalpha- and IL-1beta-mediated activation of NF-kappaB but that undifferentiated HT29-D4 cells were unresponsive to IL-1beta.

Monolayer versus aggregate balance in survival process for EGF-induced apoptosis in A431 carcinoma cells: Implication of ROS-P38 MAPK-integrin alpha2beta1 pathway.

A431 cells escape EGF-induced apoptosis by forming cell aggregates. We show that these clusters migrate and merge with neighboring ones, resulting in larger structures composed of a multilayer central (3D) population surrounded by a cell monolayer (2D). We found that after 48 hr of 10 nM EGF treatment, 3D structure formation correlates with alpha2beta1 integrin upregulation.

Purification and identification of a Ca(2+)-pectate binding peroxidase from Arabidopsis leaves.

A protein fraction was obtained from Arabidopsis (Arabidopsis thaliana, L.) leaf extract by affinity chromatography through a Ca(2+)-pectate/polyacrylamide gel. Further purification by preparative isoelectric focusing and SDS PAGE allowed the separation of a peroxidase that was identified as being peroxidase AtPrx34 (AtprxCb, accession number X71794) by N-terminal amino acid microsequencing.

The plasma membrane-associated NADH oxidase of spinach leaves responds to blue light.

The plasma membrane-associated NADH oxidase (NOX) of spinach leaf disks is characterized by oscillations in activity with a regular period length of ca. 24 min. Within a single population of plants exposed to light at the same time, NOX activities of all plants function synchronously.

Analysis and expression of the class III peroxidase large gene family in Arabidopsis thaliana.

Higher plants possess a large set of the classical guaiacol peroxidases (class III peroxidases, E.C. 1.

The novel non-glycosylated invertase from Candida utilis (the properties and the conditions of production and purification).

The Candida utilis yeast, which is cultivated in liquid media enriched with saccharose, synthesizes the well-known invertase of 300 kDa (EC 3.2.1.

Are hyperhydric shoots of Prunus avium L. energy deficient?

The content of oxidized and reduced pyridine nucleotides and some enzymatic activities of the oxidative pentose phosphate and glycolytic pathways were compared in normal (NS, growing on agar) and hyperhydric (HS, growing on gelrite) shoots of Prunus avium L. after 4 weeks of in vitro culture. The chlorophyll fluorescence from leaves and the redox capacity of the plasma membrane (reduction of exogenously added ferricyanide) of both types of shoots were recorded.