Protein phosphatase 2A alleviates cadmium toxicity by modulating ethylene production in Arabidopsis thaliana

Abstract

Cadmium (Cd) is phytotoxic and detoxified primarily via phytochelatin (PC) complexation in Arabidopsis. Here, we explore Cd toxicity responses and defence mechanisms beyond the PC pathway using forward genetics approach. We isolated an Arabidopsis thaliana Cd‐hypersensitive mutant, Cd‐induced short root 1 (cdsr1) in the PC synthase mutant (cad1‐3) background. Using genomic resequencing and complementation, we identified PP2A‐4C as the causal gene for the mutant phenotype, which encodes a catalytic subunit of protein phosphatase 2A (PP2A). Root and shoot growth of cdsr1 cad1‐3 and cdsr1 were more sensitive to Cd than their respective wild‐type cad1‐3 and Col‐0. A mutant of the PP2A scaffolding subunit 1A was also more sensitive to Cd. PP2A‐4C was localized in the cytoplasm and nucleus and PP2A‐4C expression was downregulated by Cd in cad1‐3. PP2A enzyme activity was decreased in cdsr1 and cdsr1 cad1‐3 under Cd stress. The expression of 1‐aminocyclopropane‐1‐carboxylic acid synthase genes ACS2 and ACS6 was upregulated by Cd more in cad1‐3 and cdsr1 cad1‐3 than in Col‐0 and the double mutant had a higher ACS activity. cdsr1 cad1‐3 and cdsr1 overproduced ethylene under Cd stress. The results suggest that PP2A containing 1A and 4C subunits alleviates Cd‐induced growth inhibition by modulating ethylene production.

Differences in Cadmium Accumulation, Detoxification and Antioxidant Defenses between Contrasting Maize Cultivars Implicate a Role of Superoxide Dismutase in Cd Tolerance

“…Apparently the deficiency of PCs production in pcs mutant decreased Cd tolerance compared to WT plants [89], while mutant plants overproduced PCs showed a higher tolerance against Cd-stress [89]. Moreover, the higher stimulation of GST shown by TG than WT reveals an activated sequestration of PCs in vacuole as well as the removal of the toxic lipid peroxides [19].…”

GsERF1 enhances Arabidopsis thaliana aluminum tolerance through an ethylene-mediated pathway

“…These results are similar to those found in other studies in which the ASC1 , ASC2 , and ASC5 genes associated with ethylene synthesis increased under NaHCO 3 stress in GmERF7 -overexpressing lines [ 28 ]. Protein phosphatase 2A can reduce the toxicity of cadmium by regulating ethylene production in Arabidopsis, and ASC2 and ASC6 were found to be upregulated under cadmium stress [ 49 ]. In the present study, the root elongation advantage of transgenic Arabidopsis no longer occurred when ACC was added to the aluminum treatment solution (Fig.…”

Molecular mechanisms underlying the toxicity and detoxification of trace metals and metalloids in plants

“…In contrast, the protein phosphatase AtPP2A plays a counterbalancing role by dephosphorylating AtACS6, thus preventing excessive production of ethylene (Skottke et al, 2011; Chen et al, 2020b). Mutation in an AtPP2A subunit gene aggravates Cd toxicity in A. thaliana by increasing ethylene production (Chen et al, 2020b). A. thaliana AtEIN3/AtEIL1 are transcription factors involved in ethylene signaling, and ein3‐1 eil1‐1 double mutant is more tolerant to Cd due to repressed ethylene signaling (Ju and Chang, 2015; Kong et al, 2018).…”

“…Cadmium stress increases the production of ethylene in A. thaliana , pea and bean (Fuhrer, 1982; Rodríguez‐Serrano et al, 2006; Chen et al, 2020b). Cadmium stress upregulates the expression AtACS2 and AtACS6 in A. thaliana , which encode aminocyclopropane‐1‐carboxylic acid synthase responsible for the biosynthesis of ethylene (Schellingen et al, 2014).…”