Cadmium tolerance and antioxidative defenses in hairy roots of the cadmium hyperaccumulator, Thlaspi caerulescens

Abstract

Plant species capable of hyperaccumulating heavy metals are of considerable interest for phytoremediation and phytomining. This work aims to identify the role of antioxidative metabolism in heavy metal tolerance in the Cd hyperaccumulator, Thlaspi caerulescens. Hairy roots of T. caerulescens and the non-hyperaccumulator, Nicotiana tabacum (tobacco), were used to test the effects of high Cd environments. In the absence of Cd, endogenous activities of catalase were two to three orders of magnitude higher in T. caerulescens than in N. tabacum. T. caerulescens roots also contained significantly higher endogenous superoxide dismutase activity and glutathione concentrations. Exposure to 20 ppm (178 microM) Cd prevented growth of N. tabacum roots and increased hydrogen peroxide (H(2)O(2)) levels by a factor of five relative to cultures without Cd. In contrast, growth was maintained in T. caerulescens, and H(2)O(2) concentrations were controlled to low, nontoxic levels in association with a strong catalase induction response. Treatment of roots with the glutathione synthesis inhibitor, buthionine sulfoximine (BSO), exacerbated H(2)O(2) accumulation in Cd-treated N. tabacum, but had a relatively minor effect on H(2)O(2) levels and did not reduce Cd tolerance in T. caerulescens. Lipid peroxidation was increased by Cd treatment in both the hyperaccumulator and non-hyperaccumulator roots. This work demonstrates that metal-induced oxidative stress occurs in hyperaccumulator tissues even though growth is unaffected by the presence of heavy metals. It also suggests that superior antioxidative defenses, particularly catalase activity, may play an important role in the hyperaccumulator phenotype of T. caerulescens.

Induction of in vitro roots cultures of Thypha latifolia and Scirpus americanus and study of their capacity to remove heavy metals

“…In the particular case of Thlaspi caerulescens the analysis of root cell wall fractions revealed that the hairy roots partitioned virtually all the Cd uptake by the biomass in the cell wall fraction for 7 to 10 days before allowing passage into the symplast (Nedelkoska and Doran, 2000). The mechanism of Cd hyperaccumualtion in this species seems to be related to an efficient antioxidative defense, particularly an enhanced catalase activity (Boominathan and Doran, 2003). Further studies will be required to define the specific mechanisms of tolerance to Pb, Cr and Mn in S. americanus root cultures.…”

Phytoremediation: The Application of Vermicompost to Remove Zinc, Cadmium, Copper, Nickel and Lead by Sunflower Plant

“…According to Chaignon and Hinsinger (2003), higher concentrations of copper can inhibit root growth before shoot growth and can accumulate in the roots without any significant increase in its content of the aerial parts. Previous studies have demonstrated that growth of T. caerulescens roots was essentially unaffected by 20 ppm concentration of cadmium relative to the control cultures without cadmium (Boominathan and Doran, 2003). Root density and the depth of rooting are particularly significant in the context of phytoremediation.…”

“…Higher Cd concentrations are generally observed in plants grown on soil subjected to the metal-processing industry, sludge application, and long-term fertilization, with up to 70 mg Cd kg -1 DM in lettuce (Gerard et al, 2000). Moreover, many studies have demonstrated that Cd taken up by plants accumulates at higher concentrations in the roots than in the leaves (Boominathan and Doran, 2003). Alloway (1995) reported that Alyssum species which are naturally adapted to serpentine soils can accumulate over 2% Ni.…”

Effects of Cadmium Stress on Root Tip Cells and Some Physiological Indexes in Allium Cepa Var. Agrogarum L.

“…In plant cells, cadmium tends to be stored in the apoplast and in vacuoles, which may contribute to Cd tolerance in hyperaccumulator plants and common crops (Boominathan and Doran, 2003;Ma et al, 2005;Liu et al, 2007). Cadmium may cause growth inhibition related to reduction of mitotic activity, induction of chromosome aberrations, toxicity to nucleoli in apical meristems (Liu et al, 2003(Liu et al, /2004Zhang et al, 2009;Qin et al, 2010), damage of macromolecules, mainly proteins and lipids (Skórzyńska-Polit and Krupa, 2006) and DNA (Li et al, 2005), and disturbance of the organization of the microtubular cytoskeleton in interphase and mitotic cells Liu et al, 2009).…”