2011 南瓜中的硅转运体.pdf

The Plant Journal (2011) 66, 231–240 doi: 10.1111/j.1365-313X.2011.04483.x Isolation and functional characterization of an influx silicon transporter in two pumpkin cultivars contrasting in silicon accumulation 1,† 1,† 1 2 1,* Namiki Mitani , Naoki Yamaji , Yukiko Ago , Kozo Iwasaki and Jian Feng Ma 1Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan, and 2Faculty of Agriculture, Kochi University, Otsu 200, Monobe, Nankoku-shi, Kochi 783-8502, Japan Received 20 July 2010; revised 16 December 2010; accepted 22 December 2010; published online 21 February 2011. * For correspondence (fax (81) 86 434 1209; e-mail maj@rib.okayama-u.ac.jp). †These authors contributed equally to this work. SUMMARY 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