Antioxidant gene responses to ROS-generating xenobiotics in developing and germinated scutella of maize.

There is circumstantial evidence implicating reactive oxygen species (ROS) in the highly ordered temporal and spatial regulation of expression of the Cat and Sod antioxidant genes during seed development and germination in maize. In order to understand and provide experimental data for the regulatory role of ROS, the expression patterns of the Cat1, Cat2, Cat3, GstI, Sod3, Sod4, and Sod4A genes, as well as catalase (CAT) and superoxide dismutase (SOD) activity responses, were examined after treatments with ROS-generating xenobiotics in developing and germinated maize scutella. CAT and SOD activities increased at both stages in response to each xenobiotic examined in a dose-dependent and stage-specific manner.

The maize alternative oxidase 1a (Aox1a) gene is regulated by signals related to oxidative stress.

We isolated and characterized the expression of Aox1a, a member of the maize alternative oxidase (Aox) small multigene family. Aox1a consists of four exons interrupted by three introns and its promoter harbors diverse stress-specific putative regulatory motifs pointing to complex regulation and response to multiple signals. Responses of Aox1a to such signals were examined and compared with those of maize glutathione S-transferase I (GstI), a typical oxidative stress inducible gene.

Salt-induced antioxidant metabolism defenses in maize (Zea mays L.) seedlings.

Salinity alters general metabolic processes and enzymatic activities, causing increased production of reactive oxygen species (ROS). Expression of antioxidant defense genes would, in turn, be triggered to defend the cell against oxidative damage. We report that salt disturbed antioxidant metabolism in maize seedlings, causing detrimental effects on the growth and development of maize plantlets, increased hydrogen peroxide production and altered antioxidant activities and transcripts profiles.

Altered Cu metabolism and differential transcription of Cu/ZnSod genes in a Cu/ZnSOD-deficient mutant of maize: evidence for a Cu-responsive transcription factor.

Maize inbred line A351 exhibits extremely low levels of Cu/Zn superoxide dismutase (SOD) isozymes, three cytosolic and one chloroplastic, which are increased by supplying copper to near-toxic concentrations. Activities of the copper enzymes cytochrome c oxidase and ascorbate oxidase are also reduced. The level of expression of the maize copper chaperone for SOD is normal to elevated.

Oxidative stress responses--what have genome-scale studies taught us?

Oxidative stress arises from an imbalance between generation and elimination of reactive oxygen species, often leading to cell death. Genomic tools are expanding our understanding of the antioxidant defenses aerobes have evolved and the recently discovered role(s) of reactive oxygen species in signaling.

Catalase gene expression in response to auxin-mediated developmental signals.

The effect of auxin on maize catalase gene expression was examined at several different developmental stages during embryo and seedling development. All three catalase genes and their respective proteins were induced by both natural and synthetic auxin in immature embryos. Total catalase (CAT) activity increased dramatically in response to high concentrations of auxin, with CAT-2, which is not normally expressed at this stage, being the isozyme most responsible for the increase.

Molecular evolution and structure--function relationships of the superoxide dismutase gene families in angiosperms and their relationship to other eukaryotic and prokaryotic superoxide dismutases.

This study assesses whether the phylogenetic relationships between SODs from different organisms could assist in elucidating the functional relationships among these enzymes from evolutionarily distinct species. Phylogenetic trees and intron positions were compared to determine the relationships among these enzymes. Alignment of Cu/ZnSOD amino acid sequences indicates high homology among plant sequences, with some features that distinguish chloroplastic from cytosolic Cu/ZnSODs.