Transition metals: A double edge sward in ROS generation and signaling

Abstract

Recently, reactive oxygen species (ROS) have emerged as important signaling molecules mediating a broad range of plant adaptive and developmental responses. In plant cells, both photosynthetic and respiratory electron-transport chains, as well as the NADPH oxidases and peroxidases are involved in ROS generation. 1 ROS have been shown to regulate gene expression and signaling transduction pathways and, as such, can control numerous processes, like root gravitropism, hypersensitive response to pathogens, stomatal closure and cell expansion and development. 1-5 During pathogen attack, programmed cell death (PCD) is induced in order to isolate cells and therefore avoiding pathogen spread. ROS play a crucial role in this signaling network. 6 In many cases, ROS production is genetically programmed and is induced during development. Generation of singlet oxygen induces controlled PCD in aleurone cells, leaf senescence, tracheary elements maturation or trichome development. 4 While ROS control over numerous adaptive and developmental responses is absolutely essential, a controlled balance of ROSproducing and ROS-scavenging systems must be kept to ensure an accurate execution of signaling without provoking toxicity. Several types of ROS may be formed in plant cells. These forms can be poorly reactive (non-radicals, such as H 2 O 2 or O 3 ) or can Transition metals such as iron (Fe) and Copper (Cu) are essential for plant cell development. At the same time, due their capability to generate hydroxyl radicals they can be potentially toxic to plant metabolism. Recent works on hydroxyl-radical activation of ion transporters suggest that hydroxyl radicals generated by transition metals could play an important role in plant growth and adaptation to imbalanced environments. in this mini-review, the relation between transition metals uptake and utilization and oxidative stress-activated ion transport in plant cells is analyzed, and a new model depicting both apoplastic and cytosolic mode of ROS signaling to plasma membrane transporters is suggested.

The lime–silicate question

“…The toxicity of ROS has been discussed in numerous reviews (e.g., Choudhury et al, 2013;Rodrigo-Moreno et al, 2013;Shahid et al, 2014). Fe toxicity might be a problem particularly for the plants of acid soils where Fe is readily available.…”

Functional analyses of major cancer-related signaling pathways in Alzheimer's disease etiology

“…Increasing evidence demonstrates that ROS or other free radicals in the AD brain are largely derived from mitochondrial dysfunction [207], Aβ-mediated processes [208], transition metal accumulation [209] and genetic alterations ( Presenilin mutations) [210]. Both neurons containing NFT and AD brains with extensive Aβ deposits show very lower levels of 8-hydroxyguanosine (8OHG), a marker of oxidative damage [205, 211].…”

Polyamines control of cation transport across plant membranes: implications for ion homeostasis and abiotic stress signaling

“…Being a transition metal, Fe is highly redox active and, in the presence of H 2 O 2 , can mediate production of the hydroxyl radical through the Fenton reaction (Rodrigo-Moreno et al, 2013). This may cause lipid peroxidation and damage to key cellular structures as well as result in a massive K + exodus from the cytosol mediated by •OH-activated K + -selective outward rectifying (Demidchik et al, 2010) and non-selective K + permeable (Zepeda-Jazo et al, 2011) channels.…”