Reciprocal Interactions between Cadmium-Induced Cell Wall Responses and Oxidative Stress in Plants

Abstract

Cadmium (Cd) pollution renders many soils across the world unsuited or unsafe for food- or feed-orientated agriculture. The main mechanism of Cd phytotoxicity is the induction of oxidative stress, amongst others through the depletion of glutathione. Oxidative stress can damage lipids, proteins, and nucleic acids, leading to growth inhibition or even cell death. The plant cell has a variety of tools to defend itself against Cd stress. First and foremost, cell walls might prevent Cd from entering and damaging the protoplast. Both the primary and secondary cell wall have an array of defensive mechanisms that can be adapted to cope with Cd. Pectin, which contains most of the negative charges within the primary cell wall, can sequester Cd very effectively. In the secondary cell wall, lignification can serve to immobilize Cd and create a tougher barrier for entry. Changes in cell wall composition are, however, dependent on nutrients and conversely might affect their uptake. Additionally, the role of ascorbate (AsA) as most important apoplastic antioxidant is of considerable interest, due to the fact that oxidative stress is a major mechanism underlying Cd toxicity, and that AsA biosynthesis shares several links with cell wall construction. In this review, modifications of the plant cell wall in response to Cd exposure are discussed. Focus lies on pectin in the primary cell wall, lignification in the secondary cell wall and the importance of AsA in the apoplast. Regarding lignification, we attempt to answer the question whether increased lignification is merely a consequence of Cd toxicity, or rather an elicited defense response. We propose a model for lignification as defense response, with a central role for hydrogen peroxide as substrate and signaling molecule.

Long‐term cadmium exposure influences the abundance of proteins that impact the cell wall structure in Medicago sativa stems

“…Therefore, the plant cell wall continously undergoes structural modifications in order to adapt to the plant's development stages and environmental conditions (Caffall & Mohnen ; Loix et al . ). Plants exposed to Cd show concentration‐dependent alterations in cell wall structure.…”

The Effect of Cadmium on Oxidative Stress in Beta vulgaris

“…During Cd stress, systems capable of preventing excessive oxidation are induced or stimulated. These systems include some enzymes, such as superoxide dismutase (SOD) and peroxidases such as GPOX [24].…”

Sulfur supply as a sustainable technology for phytoextraction: its effects on cadmium uptake and detoxification in Panicum maximum Jacq. cv. Massai

“…Different tissues of Massai grass showed different responses in the primary metabolism when plants were exposed to Cd. Nevertheless, cysteine, ornithine, arginine, tryptophan, lysine, and histidine accumulated in more than one tissue, indicating that these amino acids stress in plants is the increase in the production of reactive oxygen species (ROS), which results in oxidative damages that induce lipid peroxidation CUYPERS et al, 2010;LOIX et al, 2017), as observed in the leaves of Panicum virgatum (TAI et al, 2017). Lipid peroxidation can cause the rupture of tonoplast and change the structure and amount of chloroplasts in the cells (PARMAR; KUMARI; SHARMA, 2013).…”

“…To scavenge ROS and decrease the damage caused by Cd to the photosynthetic apparatus, the plants increase the synthesis of enzymatic and non-enzymatic antioxidants, mainly of the ascorbate-glutathione cycle LOIX et al, 2017). Among the enzymes involved in this cycle, superoxide dismutase (SOD) acts on dismutation of superoxide (O2 -) in hydrogen peroxide (H2O2), while ascorbate peroxidase (APX), catalase (CAT) and guaiacol peroxidase (GPOX) reduce H2O2 to H2O (CUYPERS et al, 2010).…”

“…This result can be attributed to functions of H2O2 as opening and closing of stomata (DESIKAN et al, 2004) and regulation of genes encoding antioxidant enzymes in the leaves of plants exposed to stress conditions (NEILL et al, 2002). Although H2O2 acts in processes related to cellular defense, this ROS can cause lipid peroxidation (LOIX et al, 2017). However, there was no difference (P >0.05) in lipid peroxidation in the leaf blades of Massai grass exposed or not to Cd ( Figure 3D), differently that was observed in the stems and sheaths ( Figure 3E) and roots ( Figure 3F), where plants exposed to Cd showed higher lipid peroxidation.…”