Article pubs.acs.org/est
Genome-Wide Approach in Arabidopsis thaliana to Assess the Toxicity of Cadmium Sulfide Quantum Dots M. Marmiroli,*,†,§ L. Pagano,†,§ M. L. Savo Sardaro,† M. Villani,‡ and N. Marmiroli† †
Department of Life Sciences, University of Parma, 43100 Parma, Italy IMEM-CNR, 43214 Parma, Italy
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S Supporting Information *
ABSTRACT: Cadmium sulfide quantum dots (CdS QDs) are used in the manufacture of a number of electronics products. Their small size allows their ready entry into living cells, but as yet no attempt has been made to assess their toxicity. Our aim was to exploit two Ds transposition-induced mutant lines of Arabidopsis thaliana which tolerated exposure to CdS QDs to identify the genetic basis of their tolerance. Both a genome-wide top-down (from mutant to genes) and a bottom-up (from gene expression to phenotype) approach were applied. The differential responses of the mutants compared to the wild type showed that sensitivity to CdS QDs was unrelated to sensitivity to Cd2+ ions. A transcriptomic analysis identified a number of genes whose transcript abundance was correlated with the tolerance. The phenotype of one of the mutants was correlated with the overexpression of ELM2, an MYB containing gene visited by a Ds transposon. Segregation analysis showed that the genetic basis of CdS QDs tolerance in both mutants was monogenic. The phenotype of the other mutant could be explained by the mutation of HCF101, a gene involved in photosynthesis.
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many semiconductor electrodes.18,19 The toxicity of QDs in general has been related to their small size, high surface reactivity, photolytic activity, and mechanical stability.20 Exposure to CdS QDs has been associated with damage to the human respiratory system resulting in pulmonary inflammation, but the principal toxicological factors have not been elucidated.21 In the context of plants, the effect of exposure to CdSe QDs has been more widely examined than that to CdS QDs.22 The toxicity of Cd as a bulk material has been well reviewed.23 The aim of the present research was to use a genome-wide transcriptomic approach and a genomic approach to determine the toxic effects of exposure to CdS QDs in A. thaliana. The analysis was based on mutants obtained by Ac/Ds transposition24 and the transcriptomic data was acquired using the Affymetrix ATH1 Genome Array. The goal was to identify pathways which may be generally exploited in plants drug sensitivity, tolerance, and possibly in other eukaryotes in the response to CdS QDs. The mutant’s phenotype helped us sift through the large amount of data pouring from the microarray and sort out only the more relevant and specific gene categoriesthose involved in the resistance to CdS QDs. The experiments showed that the physiological, genetic, and genomic nature of the toxicity of CdSO4 was very different from that of CdS QDs; in particular,
INTRODUCTION Nanotechnology is a rapidly growing industrial sector, expected to achieve revenues of some $26 billion (U.S.) by 2015.1 Nanomaterials (NMs), engineered particles ranging in diameter from 1 to 100 nm, are currently exploited in the electronics, biomedical, pharmaceutical, and cosmetic industries. NMs, some synthetic and others of natural origin, have become ubiquitous in the environment. Recent attempts have been made to study the toxicity of NMs in humans and to a lesser extent their impact on the environment,2 but little is known of how they are incorporated into and how they interact with living cells. Neither their environmental and biological compartmentalization nor their chemical behavior is well understood.3−5 Over the last two decades, NMs have attracted a great deal of research interest, concentrated mostly on the determination of their structure, their physicochemical properties, and their toxicity. Various organisms have been targeted to establish the key features contributing to NM toxicity,6 but controversy remains regarding the major determinants for some NMs.7 The mode of transport and accumulation of Ag NMs has been studied in both Arabidopsis thaliana8 and various cucurbit species,9−11 the effect of ZnO NMs on germination and root growth type has been described in both ryegrass and soybean,12−14 and that of TiO2 NMs on algae, higher plants, and animals has been investigated.15,16 Gold NMs have proven to be somewhat unreactive, and so have been used in a number of therapeutic applications.17 CdS (cadmium sulfide) quantum dots (QDs) are rather small (diameter
