Exogenous 3,3′-Diindolylmethane Improves Vanadium Stress Tolerance in Brassica napus Seedling Shoots by Modulating Antioxidant Enzyme Activities

Abstract

3,3′-diindolylmethane (DIM) belongs to a family of indole glucosinolate compounds that have been shown to improve Brassica napus growth through the modulation of reactive oxygen species when applied exogenously. The B. napus cultivar AV Garnet was previously identified as a vanadium-sensitive cultivar. Therefore, in this study we investigated whether exogenous DIM could improve the vanadium tolerance of AV Garnet. We performed the following experiments: seed germination assessment, dry weight assessment, cell viability assay, chlorophyll content assay, malondialdehyde (MDA) assay, conjugated diene (CD) content assay, hydrogen peroxide (H2O2) content assay, superoxide (O2−) content determination, methylglyoxal (MG) content determination, hydroxyl radical (·OH) concentration determination, ascorbate peroxidase (APX) activity assay, superoxide dismutase (SOD) activity assay, glyoxalase I (Gly I) activity assay, glutathione S-transferase (GST) activity assay and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis for vanadium content determination. Under vanadium stress, exogenous DIM increased the seed germination percentage, shoot dry weight, cell viability and chlorophyll content. Exogenous DIM also led to a decrease in MDA, CD, H2O2, O2−, MG and ·OH, under vanadium stress in the shoots. Furthermore, DIM application led to an increase in the enzymatic activities of APX, SOD, Gly I and GST under vanadium stress. Interestingly, under vanadium stress, DIM treatment did not alter vanadium content in B. napus shoots. Our results indicate that exogenous application of DIM can improve B. napus seedling shoot growth and biomass under vanadium stress by priming the antioxidant enzymes via reactive oxygen species (ROS) signaling.

Methylglyoxal improves zirconium stress tolerance in Raphanus sativus seedling shoots by restricting zirconium uptake, reducing oxidative damage, and upregulating glyoxalase I

“…Therefore, we hypothesize that the chlorophyll b improvement by MG under the Zr stress could be as an indirect stress only regulation which is only induced under stress conditions. In a previous study, we also observed the same indirect regulation of chlorophyll b by signaling molecule 3,3′-diindolylmethane (DIM) under vanadium (V) stress in B. napus 18 which supports our hypothesis. The increase in Zr content could have led to a reduction of magnesium (Mg) ions which could also explain the reduction observed.…”

“…However, the concentrations of O 2 •− , H 2 O 2 and · OH have never been measured in MG-only treated plants. Nonetheless, we hypothesize that MG increases O 2 •− and H 2 O 2 for signaling purposes and our hypothesis is supported by Gokul et al 18 which observed increases in O 2 •− and H 2 O 2 but not · OH in B. napus in response to DIM. In our study, exogenous MG led to an endogenous increase in MG and this was also observed in Zea mays by Wang et al 39 .…”

“…The exact mode of Zr induced reduction in plant growth or modification of enzymes is not well understood but Shahid et al 15 speculates that Zr toxicity leads to overproduction of ROS (H 2 O 2 , O 2 •− and ·OH), which subsequently incur lipid damage and cell death. CD and MDA are constituents of membrane lipids and serve as important biomarkers of lipid peroxidation in plants under stress 18 . In addition, heavy metal stress can induce the continuous production of a reactive α, β-dicarbonyl ketoaldehyde called MG 19 which can inhibit cell proliferation and cause protein degradation in plants 20 .…”

“…MG production under Zr stress has not been investigated to date. Nonetheless, plants use enzymatic defense systems SOD and APX to combat downstream heavy metal toxicity from ROS buildup (H 2 O 2 , O 2 •− , and ·OH) and Gly I to reduce toxic MG buildup in affected cells 18 .…”

Supportive effect of naringenin on NaCl-induced toxicity in Carthamus tinctorius seedlings

“…However, the effect of this compound on improving plant yield under stress has been less considered. Some studies have shown that the application of exogenous antioxidant compounds in activating the plant defense system against many stresses such as heavy metals (Sharma et al, 2021;Gokul et al, 2021), cold (Oz dan-Konakci et al, 2019 and salinity stress (Idrees et al, 2011;Azooz et al, 2013;Liu et al, 2016;Oz dan-Konakci et al, 2020). Recently, Oz dan- showed the involvement of naringenin in the improvement of growth and increment of osmotic adjustment on salt (100 mM NaCl)-stressed Phaseolus vulgaris.…”