Indole-3-butyric acid priming reduced cadmium toxicity in barley root tip via NO generation and enhanced glutathione per
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ORIGINAL ARTICLE
Indole‑3‑butyric acid priming reduced cadmium toxicity in barley root tip via NO generation and enhanced glutathione peroxidase activity Loriana Demecsová1 · Veronika Zelinová1 · Ľubica Liptáková1 · Katarína Valentovičová1 · Ladislav Tamás1 Received: 5 June 2020 / Accepted: 27 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Main conclusion Activation of GPX and enhanced NO level play a key role in IBA-mediated enhanced Cd tolerance in young barley roots. Abstract Application of exogenous indole-3-acetic acid (IAA) or an IAA precursor improves the tolerance of plants to heavy metals. However, the physiology of these tolerance mechanisms remains largely unknown. Therefore, we studied the priming effect of indole-3-butyric acid (IBA), an IAA precursor, on mild and severe cadmium (Cd) stress-induced responses in roots of young barley seedlings. IBA, similarly to mild Cd stress, significantly increased the glutathione peroxidase (GPX) activity in the apexes of barley roots, which remained elevated after the IBA pretreatment as well. IBA pretreatment-evoked high nitric oxide generation in roots effectively reduced the high superoxide level under the severe Cd stress, leading to less toxic peroxynitrite accumulation accompanied by markedly reduced Cd-induced cell death. On the other hand, the IBA-evoked changes in IAA homeostasis resulted in root growth reorientation from longitudinal elongation to radial swelling. However, the application of an IAA signaling inhibitor, following the activation of defense responses by IBA, was able to promote root growth even at high concentrations of Cd. Based on the results, it can be concluded that the application of IBA, as an effective activator of Cd tolerance mechanisms in young barley roots, and the subsequent use of an IAA signaling inhibitor for the inhibition of root morphogenic responses induced by altered auxin metabolism, results in a high degree of root Cd tolerance, helping it to withstand even the transient exposure to lethal Cd concentration without the absolute inhibition of root growth. Keywords Cell death · Indole-3-acetic acid · Reactive nitrogen species · Reactive oxygen species · Root stress responses Abbreviations DAA 1,2-Diaminoanthraquinone GPX Glutathione peroxidase IBA Indole-3-butyric acid RNS Reactive nitrogen species PCIB P-Chlorophenoxyisobutyric acid RFU Relative fluorescence unit RGI Root growth inhibition
Communicated by Dorothea Bartels. * Ladislav Tamás [email protected] 1
Institute of Botany, Plant Science and Biodiversity Centre, Slovak Academy of Sciences, Dúbravská cesta 9, 84523 Bratislava, Slovak Republic
Introduction In the past decades, it became clear that the contamination of soils with heavy metals, such as cadmium (Cd), is an environmental problem and a growing threat. Although Cd occurs naturally in soils in very low concentrations, recent reports showed that in Europe large Cd deposition can be found in Ireland, England, France, Italy, Slovenia, and Croatia (Pan
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