engleski

Molecular Mechanism of Cd Accumulation in Nicotiana glauca

Cadmium is one of the most dangerous substances on Earth and toxic for most organisms. Surprisingly, some plants can be hypertolerant and accumulate Cd in significant amounts. Researching this phenomenon is important for our understanding of metal hyperaccumulator biology. Nicotiana glauca is a tobacco plant growing in Negev desert on contaminated soil, with elevated metal content in the tissue. In this study we examine its Cd-accumulating properties and underlying molecular mechanisms in comparison with non-accumulating N. tabacum. Plants were grown on MS media with 15μM Cd for 4 weeks, harvested and dried to constant weight. Cd content was determined by ICP-OES and showed 3-fold higher shoot-to-root ratio for N. glauca in comparison with N. tabacum. 10 week-old plants were treated with 15μM Cd. After 3 days, RNA was isolated, reversely transcribed and qPCR was performed with actin gene as internal control. CIT1 showed higher constitutive expression in N. glauca roots, NRAMP-1 in shoots and NAS in the whole plant. Upon Cd treatment expression of NAS, NRAMP-1 and PCS further increased. NAS (nicotianamine synthetase) appears to have high importance for Cd-accumulation by chelating metals throughout the plant. Additionally, CIT1 (citrate synthase) possibly fosters Cd-xylem loading, while NRAMP-1 (metal transporter) participates in Cd storing into vacuoles in leaves. Our results show that N. glauca is tolerant to Cd and preferably accumulates Cd in shoots. Our future research plan includes NRAMP-1 localization assay in order to verify its role in Cd-accumulation, and investigating expression and localization of other potentially important genes for these properties.

Nicotiana glauca; cadmium; hyperaccumulation

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