Thymol Mitigates Cadmium Stress by Regulating Glutathione Levels and Reactive Oxygen Species Homeostasis in Tobacco Seedlings

Abstract

Abstract:Thymol is a famous plant-derived compound that has been widely used in pharmacy due to its antioxidant and antimicrobial properties. However, the modulation of intrinsic plant physiology by thymol remains unclear. It is a significant challenge to confer plant tolerance to Cd (cadmium) stress. In the present study physiological, histochemical, and biochemical methods were applied to investigate thymol-induced Cd tolerance in tobacco (Nicotiana tabacum) seedlings. Thymol was able to alleviate Cd-induced growth inhibition of tobacco seedlings in both dose-and time-dependent manners. Both histochemical detection and in-tube assays suggested that thymol treatment blocked Cd-induced over-generation of reactive oxygen species (ROS), lipid peroxidation, and loss of membrane integrity in both leaves and roots. Thymol decreased Cd-induced cell death that was indicated in vivo by propidium iodide (PI) and trypan blue, respectively. Thymol stimulated glutathione (GSH) biosynthesis by upregulating the expression of γ-glutamylcysteine synthetase 1 (GSH1) in Cd-treated seedlings, which may contribute to the alleviation of Cd-induced oxidative injury. In situ fluorescent detection of intracellular Cd 2+ revealed that thymol significantly decreased free Cd 2+ in roots, which could be explained by the thymol-stimulated GSH biosynthesis and upregulation of the expression of phyochelatin synthase 1 (PCS1). Taken together, these results suggested that thymol has great potential to trigger plant resistant responses to combat heavy metal toxicity, which may help our understanding of the mechanism for thymol-modulated cell metabolic pathways in response to environmental stimuli.

The role of antioxidant mechanism in photosynthesis under heavy metals Cd or Zn exposure in tobacco leaves

“…Similar to APX, GPX can also reduce H 2 O 2 . Regeneration of GSH could be achieved by reducing GR, and GSH is an antioxidant that can improve plant tolerance to environmental stresses, such as those posed by HMs (Jia et al 2016;Ye et al 2016). Under Cd exposure, our results indicate that GPX and GR activities significantly up-regulated in parallel with an increased expression of GR compared with CK, indicating that tobacco leaves may improve the tolerance to Cd by enhancing the GSH-GSSG cycle.…”

Thymol ameliorates ammonium toxicity via repressing polyamine oxidase-derived hydrogen peroxide and modulating ammonium transporters in rice root

“…The fluorescence was observed and captured with a fluorescence microscope (ECLIPSE, TE2000-S, Nikon, Melville, NY, USA) with setting of excitation 480-490 nm/emission 515-525 nm for green fluorescence (DCFH-DA and HPF) and excitation 530-540 nm/emission 610-620 nm for red fluorescence (DHE and PI). Histochemical staining of leaves was performed based on our previous study (Ye et al 2016). O 2…”

“…The relative abundance of house-keeping gene Actin was used as the internal standard to normalize the expression data. The detailed procedure can be found in our previous study (Ye et al 2016). The final expression data was clustered and presented as heatmap using Cluster 3.0 combined with Java Treeview (Shi et al 2014).…”

Thymol ameliorates 5‐fluorouracil‐induced intestinal mucositis: Evidence of down‐regulatory effect on TGF‐β/MAPK pathways through NF‐κB

“…[27] It is classified by the Food and Drug Administration, as being generally recognized as safe (GRAS). [28] Moreover, a number of studies showed that thymol reduced the key mediators of inflammation, such as cyclooxygenase (COX-2)catalyzed prostaglandin E2 (PGE2), [29] as well as inflammatory cytokines like nuclear factor kappa B (NF-κB), TNF-α, and IL-1β. [30,31] It also reduced gastric and colon inflammation induced by ethanol and acetic acid, respectively, in previous studies.…”