| text |
Reactive Oxygen Species (O2-, H2O2, and hydroxyl radical) are produced in the living cell in response to various metabolic activities, and in response to stress conditions. In plants, the majority of the ROS are produced in chloroplast during the light cycle of photosynthesis and in mitochondria during respiration. The increased amounts of intracellular ROS have been associated with cellular damage. However, recent studies suggest that ROS acts as a signaling molecule (secondary messenger) in numerous biological processes that involve programmed cell Death, seed development, root hair growth and elongation, plant defense, and acclimation to different abiotic stresses (drought, waterlogging conditions/submergence, salinity, heat, etc.). Under submergence, ethylene induces expression of RBOH gene (NADH oxidases). RBOHH protein is subsequently activated/phosphorylated by CDPK5 and/or CDPK13 and then produces O2-. This O2-. is spontaneously or enzymatically converted to H2O2, which diffuses or is transported into the cytosol. H2O2 participates in hypoxia signal transduction to modulate the expression of a set of genes encoding heat-shock proteins and other groups of ROS-mediated proteins. In addition, peroxidases play a role in the generation and neutralization of ROS during root growth.
|
