Specific stress responses to cadmium, arsenic and mercury appear in the metallophyte Silene vulgaris when grown hydroponically

Abstract

The tolerance of the metallophyte Silene vulgaris, a plant suitable for the phytostabilisation of metal(loid)contaminated soils, to arsenic (As), mercury (Hg) and cadmium (Cd) was evaluated in a semi-hydroponic culture system under controlled environmental conditions. The appearance of oxidative stress, alteration of photochemical processes and modification of biothiol content were studied as physiological parameters of metal(loid) stress in plants treated with 0, 6 and 30 mM (As, Hg or Cd) for 7 days. In spite of the metal(loid) excluder behaviour of S. vulgaris, Cd was translocated to the aerial part of the plant at a higher rate than Hg or As. The major toxic effects were observed in roots, where lipid peroxidation was increased in a dose-dependent manner. Redox enzymes such as glutathione reductase (GR) were severely inhibited by Hg, whereas GR was overexpressed. The accumulation of Cd produced a remarkable production of phytochelatins (PCs) in roots, whereas Hg and As led to modest PCs synthesis. There was a severe loss of chlorophyll content in Cd-treated plants, accompanied with a significant decrease in photosystem II efficiency (WPSII) and photochemical quenching (qP). Similar negative effects were observed in Hg-and Asexposed plants, but to a lesser degree. The exposure to the highest dose of each toxic element (30 mM) caused depletion of the light harvesting complex b1 protein. In conclusion, specific stress signatures to each metal(loid) were observed, with As being the least toxic element, suggesting that different mechanisms of tolerance were exerted. These results could be applied in future experiments to select tolerant ecotypes to optimize the phytostabilisation of metal(loid) multipolluted soils.

Antioxidant responses of peanut roots exposed to realistic groundwater doses of arsenate: Identification of glutathione S-transferase as a suitable biomarker for metalloid toxicity

“…The metalloid content in roots was higher than in shoots, showing that more than 97% of the As taken up by peanut plants was retained in the root system. This is a common response of non-hyperaccumulator plants where roots accumulate the major metalloid concentration (Dhankher et al 2006;Carbonell-Barrachina et al 2009;Sobrino-Plata et al 2013). Probably, this toxic level of contaminant inhibited peanut growth, metabolism and transport allowing the passage of the metalloid to shoots disrupting the root protective "barrier" against As(V).…”

“…These enzymes constitutes the major ROS scavenging mechanisms of plants (Mittler 2012) and their induction under different metal (loid) treatments has been demonstrated in several species (Sharma and Dietz, 2009). One of the most studied antioxidant metabolite essential to cope with the oxidative stress induced by toxic elements such as Cd, Hg and As is the tripeptide GSH (Li et al 2006;Bianucci et al 2012;Sobrino-Plata et al 2013). GSH transits from its reduced form (thiol) to its oxidized form (GSSG, disulfide), keeping a strong reducing environment in the cell which plays an important role in…”

Structural, physiological and genetic diversification of Silene vulgaris ecotypes from heavy metal-contaminated areas and their synchronous in vitro cultivation

“…For S. vulgaris, the complexation of toxic ions with organic acids (Harmens et al 1994) or free amino acids (Nadgórska-Socha et al 2009) has been demonstrated. Many experiments have indicated the important role of phytochelatins and glutathione in the response of S. vulgaris to HMs (Nadgórska-Socha et al 2009;Sobrino-Plata et al 2013;Koszelnik-Leszek 2017). Compared to the abundant knowledge on tolerance strategy in S. vulgaris, relatively little is known about the antioxidant machinery preventing oxidative stress which occurred as a consequence of toxic ion penetration into the protoplast.…”

Sulphur and biothiol metabolism determines toxicity responses and fate of mercury in Arabidopsis

“…Strong GR inhibition occurred in roots of cad2-1 ,pad2-1 and rax1-1 treated with 10 μM Hg for 72 h, which also suffered extensive alterations in membrane proteins (i.e., degradation of H + -ATPase and strong inhibition of NADPH-oxidase; Sobrino-Plata et al, 2014b). The GR inhibition appears to be triggered specifically by Hg over certain concentrations inMedicago sativa or Silene vulgaris , whereas other toxic elements usually lead to an enhanced activity (Sobrino-Plata et al, 2013;2009), as can be used as a marker of Hg-stress. Besides the strong GR inhibition, there were minor and non-consistent changes in the proportion of GSSG in the analysed Arabidopsis genotypes (Table 1).…”