Expression of Cereal Peroxidase and Oxalate Oxidase Genes in Tobacco Results in Alterations in Plant Development and Programmed Cell Death in Cell Cultures

Abstract

Peroxidases and oxalate oxidases are enzymes associated with the production and scavenging of hydrogen peroxide in plants. Peroxidases can influence developmental processes, including auxin metabolism (Normanly, 1997) and lignification (Mader and Amberg-Fisher, 1982), as well as responses to biotic (Thordal-Christensen et al., 1992) and abiotic stresses (Jansen et al., 2001). Oxalate oxidase (germin) is although believed to have several roles in plant development and response to pathogens (Bernier and Berna, 2001), and has recently been shown to afford resistance to insect predation (Ramputh et al., 2002). Hydrogen peroxide (H₂O₂), levels might reasonably be expected to be altered by modifications in activities of peroxidase (H₂O₂-utilising) and oxalate oxidase (H₂O₂-generating) enzymes. H₂O₂ itself may act as a signaling molecule, triggering programmed cell death and the production of lignified cells. This may be defence related, as in the “oxidative burst” associated with hypersensitive response to pathogens (Levine et al., 1994), or connected to normal developmental processes, such as xylogenesis. The latter involves both programmed cell death, and the action of peroxidase in the cross-linking of lignin precursors.