Ethylene promotes cadmium‐induced root growth inhibition through EIN3 controlled XTH33 and LSU1 expression in Arabidopsis

Abstract

Cadmium (Cd) stress is one of the most serious heavy metal stresses limiting plant growth and development. However, the molecular mechanisms underlying Cd-induced root growth inhibition remain unclear. Here, we found that ethylene signalling positively regulates Cd-induced root growth inhibition. Arabidopsis seedlings pretreated with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid exhibited enhanced Cd-induced root growth inhibition, whereas the addition of the ethylene biosynthesis inhibitor aminoethoxyvinyl glycine decreased Cd-induced root growth inhibition. Consistently, ethylene-insensitive mutants, such as ein4-1, ein3-1 eil1-1 double mutant, and EBF1ox, displayed an increased tolerance to Cd. Furthermore, we also observed that Cd inhibited EIN3 protein degradation, a process that was regulated by ethylene signalling. Genetic and biochemical analyses showed that EIN3 enhanced root growth inhibition under Cd stress through direct binding to the promoters and regulating the expression of XTH33 and LSU1, which encode key regulators of cell wall extension and sulfur metabolic process, respectively. Collectively, our study demonstrates that ethylene plays a positive role in Cd-regulated root growth inhibition through EIN3-mediated transcriptional regulation of XTH33 and LSU1 and provides a molecular framework for the integration of environmental signals and intrinsic regulators in modulating plant root growth.

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

“…Similarly, Kong et al (2018) showed that the ethylene-insensitive mutants ein4-1 and ein3-1 eil1-1, and EBF1 overexpression lines, which had repressed ethylene signalling, were more tolerant to Cd, whereas increased ethylene sensitivity in the mutant ebf1-1 (more EIN3 protein accumulation) and the constitutive ethylene response ctr1-1 mutant or in the overexpressing lines of EIN3 and EIL1 were more sensitive to Cd. These results suggest that ethylene signalling is involved in the early responses to Cd stress.…”

“…Inhibition of primary root growth is a typical phenotype of Cd toxicity in Arabidopsis (Howden & Cobbett, ; Kong et al, ). Based on this phenotype, we isolated a Cd‐hypersensitive mutant, cdsr1 cad1‐3 , in the cad1‐3 background that lacks the functional PCS (Howden, Goldsbrough, et al, ).…”

“…Ethylene is a well‐known negative regulator of cell cycle and growth (Swarup et al, ). Inhibition of ethylene biosynthesis by AVG was found to alleviate Cd inhibition of root growth (Kong et al, ), whereas the acs2 acs6 double mutant was less sensitive to Cd than wild type (Schellingen et al, ). In our study, AVG addition also alleviated Cd sensitivity, whereas ACC addition increased Cd sensitivity in both cad1‐3 and cdsr1 cad1‐3 (Figure S5a,b).…”

“…The ethylene signalling pathway in plants comprises four modules, including a phosphotransfer relay, an EIN2‐based unit, a ubiquitin‐mediated protein degradation component, and a transcriptional cascade (Alonso & Stepanova, ). Ethylene‐insensitive mutants, such as ein4‐1 and ein3‐1 eil1‐1 double mutant, are more tolerant to Cd, suggesting that ethylene is closely related to Cd toxicity responses (Kong et al, ). However, how Cd regulates ethylene production remains unclear.…”

Peer Review #2 of "Mulberry EIL3 confers salt and drought tolerances and modulates ethylene biosynthetic gene expression (v0.1)"

“…In model plants, EIN3/EILs are involved in many aspects of the life cycle, including seed germination, soil emergence, seedling development, leaf senescence, pigments biosynthesis, light perception, and abiotic stress responses (Kim et al, 2017;Zhong et al, 2014;An et al, 2018;Yu et al, 2013;Yu et al, 2016). Additionally, the regulatory functions of EIN3/EILs in response to abiotic stresses have also attracted considerable attention (Zhang et al, 2011;Cui et al, 2015;Shi et al, 2012;Kong et al, 2018;Peng et al, 2014). However, there are no reports on the functions of EIN3/EILs in the abiotic stress tolerance of woody plants, including mulberry.…”