Effects of exogenous sulfur on alleviating cadmium stress in tartary buckwheat

Abstract

Supplying exogenous sulfur-rich compounds increases the content of glutathione(GSH) and phytochelatins(PCs) in plant tissues, enabling plants to enhance their cellular defense capacity and/or compartmentalize Cadmium(Cd) into vacuoles. However, the mechanism by which surplus S modulates tolerance to Cd stress in different tissues need further investigation. In the present study, we found that supplementing the tartary buckwheat( Fagopyrum tararicum ) exposed to Cd with surplus S reversed Cd induced adverse effects, and increased Cd concentrations in roots, but decreased in leaves. Further analysis revealed that exogenous S significantly mitigated Cd-induced oxidative stress with the aids of antioxidant enzymes and agents both in leaves and roots, including peroxidase(POD), ascorbate peroxidase(APX), glutathione peroxidase(GPX), glutathione S-transferase(GST), ascorbic acid(AsA), and GSH, but not superoxide dismutase(SOD) and catalase(CAT). The increased Cd uptake in root vacuoles and decreased translocation in leaves of exogenous S treated plants could be ascribed to the increasing Cd binding on cell walls, chelation and vacuolar sequestration with helps of non-protein thiols(NPT), PCs and heavy metal ATPase 3(FtHMA3) in roots, and inhibiting expression of FtHMA2 , a transporter that helps Cd translocation from roots to shoots. Results provide the fundamental information for the application of exogenous S in reversal of heavy metal stress.

SLIM1 Transcription Factor Promotes Sulfate Uptake and Distribution to Shoot, Along with Phytochelatin Accumulation, Under Cadmium Stress in Arabidopsis thaliana

“…Reduced Cd accumulation in roots associated with a less tolerant Cd phenotype was also observed in the disruption lines of SULTR1;2 [51]. In addition to this, sulfate application increased Cd concentrations in the roots of wheat, mustard, and buckwheat plant [32,35,75]. However, these findings should be considered in relation to the general suggestion that the ability of plants to accumulate higher heavy metal levels in shoots rather than in roots is associated with a higher heavy metal tolerance [8].…”

“…Cd exposure-induced synthesis of GSH and PC stimulates S assimilation by Cys, a major substrate for GSH synthesis [28][29][30][31]. Recent studies reported the close relation between sulfur availability and increased plant tolerance to Cd stress [32][33][34][35][36]. S assimilation in plants starts with the uptake of sulfate by the rhizosphere via sulfate transporters (SULTR) [30,31,37].…”

Cadmium Uptake by Wheat (Triticum aestivum L.): An Overview

“…Furthermore, S may have contrasting effects in crops. Low S content improves crop growth, whereas high S content limits nitrogen uptake, thereby diminishing crop production; hence, a proper level of S is vital [74]. Shi et al [73] found that the use of sodium sulfate enhances root Cd concentrations by up to 39%.…”

“…Shi et al [73] found that the use of sodium sulfate enhances root Cd concentrations by up to 39%. Lu et al [74] indicated that enhancing Cd uptake via root vacuoles and reducing translocation in shoots under S-treated plants may be attributed to the increasing Cd binding on cell walls, chelation, and vacuolar sequestration with the support of nonprotein thiols, phytochelatins, and heavy metal ATPases in roots; it may also prevent the expression of transporters that support Cd translocation from roots to shoots.…”

Antioxidant activity as a response to cadmium pollution in three durum wheat genotypes differing in salt-tolerance

“…We can assume that higher Cd concentration (5 mg kg −1 DM) was toxic enough to block the processes involved in the transport of assimilates and ions to the seeds. Lu et al [56] observed a similar phenomenon in Fagopyrum tataricum. They stated that in plants exogenously treated with sulfur, increased Cd uptake in root vacuoles and its decreased translocation to the leaves can result from enhanced Cd binding by cell walls, chelation and vacuolar sequestration with nonprotein thiols, and inhibited transport of Cd from roots to shoots.…”