Role of reactive oxygen species-generating enzymes and hydrogen peroxide during cadmium, mercury and osmotic stresses in barley root tip

Abstract

The effect of cadmium (Cd) on the expression and activity of NADPH oxidase, peroxidase and oxalate oxidase as well as on the expression of aquaporins and dehydrins was studied in barley root tip. The root tip represented intact apical part of the barley root containing the root cap, meristems and elongation zone. Except stress induced by Cd, barley root tips were analysed after their exposure to phytotoxic concentration of mercury (Hg)-, hydrogen peroxide (H2O2)- or polyethylene glycol (PEG)-induced water stress in order to compare the Cd-induced changes with changes induced by these other stress factors. Cd, Hg, H2O2 and with some exceptions also PEG treatments caused similar alterations in the gene expression of reactive oxygen species (ROS)-generating and water deficiency-related genes, and in the activity of ROS-generating enzymes. These evidences support our opinion that ROS accumulation and water imbalance are the common symptoms of these stress factors and that the elevated production of H2O2 plays, probably as a signal molecule, a key role in the induction of plant responses to abiotic stresses in barley root tip. On the other hand, H2O2 at permanent high concentration is probably the main toxic factor during stress conditions.

Elevated indole-3-acetic acid peroxidase activity is involved in the cadmium-induced hydrogen peroxide production in barley root tip

“…Our results showed that in addition to the activation of IAA-POD activity by exogenously added IAA also H 2 O 2 is involved in the activation of IAA-POD. The generation of ROS by several enzymes is a general syndrome of plants under Cd stress (Garnier et al 2006;Ortega-Villasante et al 2007;Tamás et al 2010). In barley, we have previously reported that both superoxide and hydrogen peroxide production was markedly induced at the presence of Cd (Tamás et al 2009).…”

“…In spite of that Cd is a non-redox-active metal, it has been suggested that one of the key factors responsible for these changes is the alteration in ROS production. Apart from the Cd-induced inhibition of antioxidant systems, the enhanced production of ROS has been reported through the activation of ROS-generating enzymes including NADPH oxidase, oxalate oxidase and extracellular PODs (Garnier et al 2006;OrtegaVillasante et al 2007;Tamás et al 2010).…”

The Influence of Metal Stress on the Availability and Redox State of Ascorbate, and Possible Interference with Its Cellular Functions

“…In different studies, a correlation between growth reduction and increased lignin content in roots has been considered as a typical event in defense against metal stress in different plant species [79–85]. Lignification can limit the cell expansion, the capacity for nutrient uptake and thus the ability to sustain plant growth [47].…”

“…Moreover, the lignin biosynthesis related enzymes, peroxidases and laccases were enhanced during Cd treatment [82]. Tamás et al [85] showed in barley seeds ( Hordeum vulgare ) exposed to 1 mM CdCl 2 that stress activated several H 2 O 2 generating enzymes, e.g., NADPH-oxidase, which probably contributes to general stress induced morphological changes of barley root tips, such as root thickening, cell wall modifications and lignification. These responses were accompanied by root growth inhibition due to the enhanced rigidification of cell wall and accelerated differentiation of root cells [85].…”

Quantitative Trait Loci for Mercury Accumulation in Maize (Zea mays L.) Identified Using a RIL Population

“…At high concentrations in soil, Hg can poison plant cells and cause physiological disorders [8], producing detrimental effects on plant growth and metabolism [9], [10]. Hg accumulation in roots prevents the uptake and transport of other mineral nutrients [11], and excess Hg in solution culture can inhibit biomass production [5].…”