Zea mays L. protein changes in response to potassium dichromate treatments M. Labra a, * , E. Gianazza b , R. Waitt c , I. Eberini b , A. Sozzi b , S. Regondi b , F. Grassi d , E. Agradi b a DISAT, Universita ` di Milano-Bicocca, P.zza della Scienza 1, 20126 Milano, Italy b Dipartimento di Scienze Farmacologiche, Universita ` di Milano, via Balzaretti 9, 20133 Milano, Italy c Kennedy Institute of Rheumatology Division, Imperial College of London, Aspenlea Road, Hammersmith, London W6 8LH, UK d Dipartimento di Biologia, Universita ` degli Studi di Milano, via Celoria 26, 20133 Milano, Italy Received 7 April 2005; received in revised form 13 June 2005; accepted 28 June 2005 Available online 28 November 2005 Abstract The plant metabolic response to heavy metal stress is largely unknown. The present investigation was undertaken to examine the influence of different concentrations of potassium dichromate on the Zea mays L. plantlets. A clear effect of chromium on maize plantlets growth and seed germination was observed strating from 100–300 ppm up to 1500 ppm. In this concentration range, chromium uptake was dependent on the concentration in the medium. Metallothioneins, involved in heavy metal binding, were measured by capillary electrophoresis (CE), and showed a dose-response induc- tion. Protein profile analyzed by two-dimensional gel electrophoresis showed differential expression of several proteins. Identification of spots of upregulated proteins was performed by MALDI mass spectrometry. Results showed that pro- teins induced by heavy metal exposure are principally involved in oxidative stress tolerance or in other stress pathways. Induction of proteins implicated in sugar metabolism was also observed. Identification of factors involved in plant response may lead to a better understanding of the mechanisms involved in cell protection and tolerance. This information could be used to improve agricultural production and environmental quality. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Chromium; Metallothioneins; Proteomics; Stres-response proteins; Zea mays L. 1. Introduction Heavy metal contamination of soil has become a worldwide problem, leading to losses in agricultural yield and hazardous effects on health when the contam- inants enter the food chain. Living organisms require trace amounts of such heavy metals as cobalt, copper, iron, manganese, molybdenum, vanadium, and zinc. Excessive levels of essential metals, however, are 0045-6535/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2005.06.062 Abbreviations: SDS-PAGE, Sodium Dodecylsulfate Poly- acrylamide Gel Electrophoresis; IEF, Isoelectric Focusing; 2- DE, Two-Dimensional Gel Electrophoresis; CE, Capillary Electrophoresis. * Corresponding author. Tel.: +39 02 64482943; fax: +39 02 64482994. E-mail address: massimo.labra@unimib.it (M. Labra). Chemosphere 62 (2006) 1234–1244 www.elsevier.com/locate/chemosphere