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.