Characterization of mechanisms involved in tolerance and accumulation of Cd in Biscutella auriculata L

Abstract

Biscutella auriculata L. is one of the rare species that is able to grow in a very contaminated mining area in Villamayor de Calatrava (Ciudad Real, Spain). In an effort to understand the mechanisms involved in the tolerance of this plant to high metal concentrations, we grew B. auriculata in the presence of 125 μM Cd(NO3)2 for 15 days and analysed different parameters associated with plant growth, nitric oxide and reactive oxygen species metabolism, metal uptake and translocation, photosynthesis rate and biothiol (glutathione and phytochelatins) content. Treatment with Cd led to growth inhibition in both the leaves and the roots, as well as a reduction of photosynthetic parameters, transpiration and stomatal conductance. The metal was mainly accumulated in the roots and in the vascular tissue, although most Cd was detected in areas surrounding their epidermal cells, while in the leaves the metal accumulated mainly in spongy mesophyll, stomata and trichrome. Based on the Cd bioaccumulation (5.93) and translocation (0.15) factors, this species denoted enrichment of the metal in the roots and its low translocation to the upper tissues. Biothiol analysis showed a Cd-dependent increase of reduced glutathione (GSH) as well as the phytochelatins (PC2 and PC3) in both roots and leaves. Cd-promoted oxidative damage occurred mainly in the leaves due to disturbances in enzymatic and nonenzymatic antioxidants, while the roots did not show significant damage as a result of induction of antioxidant defences. It can be concluded that B. auriculata is a new Cd-tolerant plant with an ability to activate efficient metal-sequestering mechanisms in the root surface and leaves and to induce PCs, as well as antioxidative defences in roots.

Characterization of the biochemical basis for copper homeostasis and tolerance inBiscutella auriculataL.

“…The analysis of SOD activity through native‐PAGE showed four isoforms in control leaves, while in those with Cu treatment three of them had almost disappeared (Figure 4). The same phenomenon was observed in this species in response to Cd, which could indicate the low contribution of SOD to the mechanism of Cu and Cd tolerance in B. auriculata (Peco, Higueras, et al, 2020), while in plants exposed to Pb a considerably induction of all isoforms were observed (Peco, Campos, et al, 2020), suggesting mechanistic differences depending on the type of metal. Several evidences demonstrate changes in SOD activity depending on the Cu concentration in different plant species; low doses produced an increment in SOD activity in Boehmeria nivea and Withania somnifera , while high doses resulted in a reduction of this activity (Rout et al, 2013, Hakeem et al, 2019).…”

“…Although there are few studies in which the accumulation of PC in response to Cu has been found, it has been well documented that this is a general response to other metals such as cadmium (Peco, Higueras, et al, 2020; Wojas et al, 2010). In B. auriculata cadmium induced both PC2 and PC3 in roots and leaves (Peco, Higueras, et al, 2020), while lead only induced PC2 in roots (Peco, Campos, et al, 2020), demonstrating a metal‐dependent specific regulation of PCs synthesis. The mechanism of the action of PCs has been described for Nicotiana tabacum plants in response to cadmium, in which PCs form complexes with the metal in the cytosol and these are actively transported into the vacuole (Wojas et al, 2010).…”

“…The rest of the enzymatic activities were analysed spectrophotometrically: CAT activity (EC 1.11.1.6); POD activity; GOX activity (EC 1.1.3.1); APX activity (EC 1.11.1.11), GR activity (EC 1.6.4.2); MDHAR activity (EC 1.6.5.4) and DHAR activity (EC 1.8.5.1) as reported by Hafsi et al (2010); NADP + ‐dependent glucose‐6‐phosphate dehydrogenase enzyme (NADP‐G6PDH) (EC 1.1.1.49), NADP + ‐dependent isocitrate dehydrogenase (NADP‐IDH) (EC 1.1.1.42) and NADP + ‐dependent isocitrate dehydrogenase (NADP‐MS) (EC 4.1.3.2) as reported by León et al (2002); GST activity (EC 2.5.1.1) as described by Habig et al (1974) and S‐nitrosoglutathione reductase (GSNOR) (EC 1.2.1.46) as described by Ortega‐Galisteo et al (2012). Details of the enzymatic assays are given by Peco, Campos, et al (2020).…”

Influence of Biochar Derived Nitrogen on Cadmium Removal by Ryegrass in a Contaminated Soil

“…Therefore, more attention must be paid to plants metabolism and molecular mechanisms to reveal the direct role of organic amendments, such as biochar, in future phytoremediation studies, as pointed out by Liu et al [50]. For example, the recent study of Peco et al [51] has found Biscutella Control SGB PLB auriculata L, a wild herbaceous species that grows on pastureland, as a new Cd-tolerant plant capable of activating efficient metal-sequestering mechanisms in the root surfaces and leaves, and of inducing phytochelatins in both parts, besides stimulating antioxidative defenses in roots.…”

The effects of cadmium on growth, some anatomical and physiological parameters of wheat (Triticum aestivum L.)

“…According to similar studies on stoma and epidermal hairs (for 1 mm 2 leaf surface); in after the applications of 0 and 125 μM Cd [68]. This could be a response for survival of the plant in applied Cd concentrations, with increased stomata and epidermal hair numbers even when the plant is under stress.…”