Identifying the Pressure Points of Acute Cadmium Stress Prior to Acclimation in Arabidopsis thaliana

Abstract

The toxic metal cadmium (Cd) is a major soil pollutant. Knowledge on the acute Cd-induced stress response is required to better understand the triggers and sequence of events that precede plant acclimation. Therefore, we aimed to identify the pressure points of Cd stress using a short-term exposure set-up ranging from 0 h to 24 h. Acute responses related to glutathione (GSH), hydrogen peroxide (H2O2), 1-aminocyclopropane-1-carboxylic acid (ACC), ethylene and the oxidative challenge were studied at metabolite and/or transcript level in roots and leaves of Arabidopsis thaliana either exposed or not to 5 µM Cd. Cadmium rapidly induced root GSH depletion, which might serve as an alert response and modulator of H2O2 signalling. Concomitantly, a stimulation of root ACC levels was observed. Leaf responses were delayed and did not involve GSH depletion. After 24 h, a defined oxidative challenge became apparent, which was most pronounced in the leaves and concerted with a strong induction of leaf ACC synthesis. We suggest that root GSH depletion is required for a proper alert response rather than being a merely adverse effect. Furthermore, we propose that roots serve as command centre via a.o. root-derived ACC/ethylene to engage the leaves in a proper stress response.

Glutathione Metabolism in Plants under Stress: Beyond Reactive Oxygen Species Detoxification

“…This suggests that GGT1 plays a role in redox signaling from the extracellular environment to internal compartments and transmits redox information important for plant adaptation to their environment [ 152 , 161 ]. In connection to this proposed role, Arabidopsis roots exposed to Cd 2+ display a robust and early transcriptional induction of GGT1 during the acute stress response phase (within the first 24 h of stress) that precedes the subsequent acclimation process [ 162 ].…”

Reactive Oxygen Species and Abiotic Stress in Plants

“…Luckily, the recent advances in technologies allowing large-scale "-omics" analyses accelerate this process. The studies in this Special Issue add valuable pieces of the puzzle related to stress responses by: (i) reporting novel potent regulators and the mechanisms through which they exert their effects [15,[17][18][19]; (ii) throwing light on previously unexplored components [16] or the pathways involved in particular stress types [11][12][13]; or (iii) exploring strategies to mitigate the detrimental effects [14]. We are confident that they will inspire further productive research in the future.…”

“…A critical role of glutathione was also suggested for counteracting cadmium (Cd) toxicity in Arabidopsis thaliana [12]. Cd and other heavy metals are major soil pollutants and can induce severe oxidative stress.…”

“…Moreover, 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene, accumulated first in the roots and later in the leaves. The authors proposed a spatial-temporal model of acute Cd responses, in which hydrogen peroxide/glutathione ratio serves as a signal that regulates Cd responses in roots and later in shoots [12].…”

Jasmonates, Ethylene and Brassinosteroids Control Adventitious and Lateral Rooting as Stress Avoidance Responses to Heavy Metals and Metalloids

“…In accordance, it has been shown that ET biosynthesis increases after Cd exposure and that the Cd-induced oxidative stress affects ET signaling, suggesting a crosstalk between the two pathways [ 85 ]. Recently, the promotion of ACC synthesis by Cd has been confirmed in Arabidopsis , and it has been proposed that the roots are the command center for ACC/ET to engage the proper Cd-stress response in the aerial organs [ 86 ]. Moreover, a crosstalk between JA and ET signaling is also active in response to Cd toxicity.…”