Cadmium-induced effects on the ethylene pathway and the link with oxidative stress in Arabidopsis thaliana

Abstract

Elevated concentrations of toxic metals such as cadmium (Cd) in soils, primarily caused by anthropogenic sources (e.g. mining), are a severe problem worldwide. Plants grown on contaminated soils accumulate Cd, which consequently enters the food chain, eliciting a major threat to the public health. In plants, Cd disturbs several developmental (e.g. growth) and physiological (e.g. photosynthesis) processes. Despite its non redox-active character, Cd is also capable of inducing the production of reactive oxygen species (ROS) at the cellular level, resulting in an oxidative challenge. Excessive ROS react with virtually all biomolecules, causing cellular damage. However, controlled levels of ROS, maintained by the antioxidative defence system, act as signal transduction molecules contributing to plant acclimation to abiotic stress such as exposure to Cd. Increasing evidence suggests an existing relation between cellular redox signalling and phytohormones, key regulators of plant growth and development, in order to control defence responses. Furthermore, the phytohormone ethylene, often considered as the ‘stress hormone’, is known to mediate hormone and redox signalling processes during abiotic stress. The stress-induced oxidative burst as well as the biosynthesis of glutathione (GSH), an important antioxidant during Cd stress, were already shown to be mediated by ethylene. Therefore, the aim of the current work was to unravel the involvement of ethylene biosynthesis and signalling during the Cd-induced oxidative challenge induced by sublethal Cd concentrations (5 and 10 µM Cd) in Arabidopsis thaliana.