Differential generation of hydrogen peroxide upon exposure to zinc and cadmium in the hyperaccumulating plant specie (Sedum alfredii Hance)

Abstract

Sedum alfredii Hance has been identified as zinc (Zn) and cadmium (Cd) co-hyperaccumulator. In this paper the relationships of Zn or Cd hyperaccumulation to the generation and the role of H 2 O 2 in Sedum alfredii H. were examined. The results show that Zn and Cd contents in the shoots of Sedum alfredii H. treated with 1000 μmol/L Zn 2+ and/or 200 μmol/L Cd 2+ increased linearly within 15 d. Contents of total S, glutathione (GSH) and H 2 O 2 in shoots also increased within 15 d, and then decreased. Total S and GSH contents in shoots were higher under Cd 2+ treatment than under Zn 2+ treatment. However, reverse trends of H 2 O 2 content in shoots were obtained, in which much higher H 2 O 2 content was observed in Zn 2+ -treated shoots than in Cd 2+ -treated shoots. Similarly, the microscopic imaging of H 2 O 2 accumulation in leaves using H 2 O 2 probe technique showed that much higher H 2 O 2 accumulation was observed in the Zn 2+ -treated leaf than in the Cd 2+ -treated one. These results suggest that there are different responses in the generation of H 2 O 2 upon exposure to Zn 2+ and Cd 2+ for the hyperaccumulator Sedum alfredii H. And this is the first report that the generation of H 2 O 2 may play an important role in Zn hyperaccumulation in the leaves. Our results also imply that GSH may play an important role in the detoxification of dissociated Zn/Cd and the generation of H 2 O 2 .

Response of ATP sulfurylase and serine acetyltransferase towards cadmium in hyperaccumulator Sedum alfredii Hance

“…Our results indicate that sulfur assimilation and cysteine synthesis increased in HE with increasing Cd levels. Previous studies proved that GSH contents were markedly higher in HE than in NHE under Cd stress (Jin et al, 2008;Chao et al, 2008), and that the total sulfur accumulation increased rapidly in HE after Cd treatment (Chao et al, 2008). Our results imply that HE enhanced sulfur assimilation pathway enzymes activities, which could be the source of sulfur for GSH synthesis and related to heavy metal accumulation.…”

Zinc Hyperaccumulation in Plants: A Review

“…The random amplified polymorphic DNA (RAPD) method was used to compare the genomic variation of Sedum hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE), and revealed that the Zn/Cd hyperaccumulation trait was related to SH-containing compounds [175]. Recently, Yang et al [176] identified molecular markers single nucleotide polymorphisms (SNPs) and simple sequence repeats (SSRs) of S. alfredii, which constitutes an important resource for genome mapping to identify hyperaccumulation and hypertolerance traits.…”

Hyperaccumulator Plants from China: A Synthesis of the Current State of Knowledge

“…75,104 Concentration of glutathione in the leaf was found to increase with increasing Zn concentrations in growth media for both of the two population types of S. alfredii. 105,106 However, it was shown that the dominant chemical form of Zn in the leaf of the hyperaccumulating population was Zn malate (Figure 3). 107 This finding is similar to that for A. halleri but not N. caerulescens (where foliar Zn was present predominantly in the form of another carboxylic acid; Zn citrate).…”