These authors contributed equally to this work.
Isolation and functional characterization of an influx silicon transporter in two pumpkin cultivars contrasting in silicon accumulation
Article first published online: 21 FEB 2011
© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd
The Plant Journal
Volume 66, Issue 2, pages 231–240, April 2011
How to Cite
Mitani, N., Yamaji, N., Ago, Y., Iwasaki, K. and Ma, J. F. (2011), Isolation and functional characterization of an influx silicon transporter in two pumpkin cultivars contrasting in silicon accumulation. The Plant Journal, 66: 231–240. doi: 10.1111/j.1365-313X.2011.04483.x
- Issue published online: 18 APR 2011
- Article first published online: 21 FEB 2011
- Accepted manuscript online: 3 JAN 2011 02:18PM EST
- Received 20 July 2010; revised 16 December 2010; accepted 22 December 2010; published online 21 February 2011.
- root stock;
A high accumulation of silicon (Si) is required for overcoming abiotic and biotic stresses, but the molecular mechanisms of Si uptake, especially in dicotyledonous species, is poorly understood. Herein, we report the identification of an influx transporter of Si in two Cucurbita moschata (pumpkin) cultivars greatly differing in Si accumulation, which are used for the rootstocks of bloom and bloomless Cucumis sativus (cucumber), respectively. Heterogeneous expression in both Xenopus oocytes and rice mutant defective in Si uptake showed that the influx transporter from the bloom pumpkin rootstock can transport Si, whereas that from the bloomless rootstock cannot. Analysis with site-directed mutagenesis showed that, among the two amino acid residues differing between the two types of rootstocks, only changing a proline to a leucine at position 242 results in the loss of Si transport activity. Furthermore, all pumpkin cultivars for bloomless rootstocks tested have this mutation. The transporter is localized in all cells of the roots, and investigation of the subcellular localization with different approaches consistently showed that the influx Si transporter from the bloom pumpkin rootstock was localized at the plasma membrane, whereas the one from the bloomless rootstock was localized at the endoplasmic reticulum. Taken together, our results indicate that the difference in Si uptake between two pumpkin cultivars is probably the result of allelic variation in one amino acid residue of the Si influx transporter, which affects the subcellular localization and subsequent transport of Si from the external solution to the root cells.