by Staff Writers
Bochum, Germany (SPX) Apr 20, 2012
In order to survive, plants should take up neither too many nor too few minerals from the soil. New insights into how they operate this critical balance have now been published by biologists at the Ruhr-Universitat in a series of three papers in the journal The Plant Cell. The researchers discovered novel functions of the metal-binding molecule nicotianamine.
"The results are important for sustainable agriculture and also for people - to prevent health problems caused by deficiencies of vital nutrients in our diet" says Prof. Dr. Ute Kramer of the RUB Department of Plant Physiology.
Plants: at the start of the food chain
How the cell tells the competitors zinc and iron apart
The membrane transport protein Zinc-Induced Facilitator1 (ZIF1) can move the metal-binding molecule from the cytosol to the vacuole - a separate area of the cell which stores substances, among other roles. Given high zinc concentrations in the cytosol, ZIF1 transports nicotianamine into the vacuole.
As a consequence, zinc ions are also transported into the vacuole and thus removed from the cytosol and the internal transport routes of the plant. The zinc is now less competition for the iron, so that iron is more readily available in the cell.
From the roots to the leaves: nicotianamine is crucial for zinc transport
When the researchers deactivated the synthesis of this molecule by means of genetic manipulation, the plants also transported less zinc from the roots to the leaves. Nicotianamine is therefore crucial for the high zinc concentration in leaves.
"In developing countries, zinc deficiency is one of the biggest dietary risk factors for health problems" Kramer explains. "Our data may provide important clues on how to breed crops with increased zinc content".
How copper gets into the plant cell
This gives a complete picture of what proteins the cell should produce in what quantities. From these data, Kramer's team identified new molecules with a critical role in the absorption of copper. The scientists demonstrated that the copper ions are first converted from the double positively charged cupric to the single positively charged cuprous form, which is essential for the following absorption in the plant. Two specific enzymes, called copper reductases, are responsible for this.
"Independently of this, we have also discovered that copper deficiency in plants triggers a secondary iron deficiency - contrary to previous expectations, and very similar to human metal metabolism".
Bibliographic records; M.J. Haydon, M. Kawachi, M. Wirtz, S. Hillmer, R. Hell, U. Kramer (2012): Vacuolar nicotianamine has critical and distinct roles under iron deficiency and for zinc sequestration in Arabidopsis, The Plant Cell, doi: 10.1105/tpc.111.095042 - U. Deinlein, M. Weber, H. Schmidt, S. Rensch, A. Trampczynska, T.H. Hansen, S. Husted, J.K. Schjoerring, I.N. Talke, U. Kramer, S. Clemens (2012): Elevated nicotianamine levels in Arabidopsis halleri roots play a key role in zinc hyperaccumulation, The Plant Cell, doi: 10.1105/tpc.111.095000 - M. Bernal, D. Casero, V. Singh, G.T. Wilson, A. Grande, H. Yang, S.C. Dodani, M. Pellegrini, P. Huijser, E.L. Connolly, S.S. Merchant, U. Kramer (2012): Transcriptome sequencing identifies SPL7-regulated copper acquisition genes FRO4/FRO5 and the copper dependence of iron homeostasis in Arabidopsis, The Plant Cell, doi: 10.1105/tpc.111.090431
Department of Plant Physiology at Ruhr-University Bochum
Farming Today - Suppliers and Technology
Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.
That is why plants grow towards the light
Brussels, Belgium (SPX) Apr 20, 2012
Have you ever wondered why stems grow upwards and roots downwards? Why plants always seem to turn towards the light and climbing plants run up the trellis rather than down? But maybe not that simple, since plant hormones - and auxin is a plant hormone - are regulated by complex combinations of various processes. Elke Barbez, Jurgen Kleine-Vehn and Jiri Friml, connected to VIB and UGent rec ... read more