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Identification of Sorbitol Transporters Expressed in the Phloem of Apple Source Leaves

Watari, Junya ; Kobae, Yoshihiro ; Yamaki, Shohei ; Yamada, Kunio ; Toyofuku, Kyoko ; Tabuchi, Toshihito ; Shiratake, Katsuhiro

In: Plant and Cell Physiology, 2004, vol. 45, no. 8, p. 1032-1041

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    Titre
    • Identification of Sorbitol Transporters Expressed in the Phloem of Apple Source Leaves
    Auteur
    • Watari, Junya. Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, 464-8601 Japan
    • Kobae, Yoshihiro. Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, 464-8601 Japan
    • Yamaki, Shohei. Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, 464-8601 Japan
    • Yamada, Kunio. Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, 464-8601 Japan
    • Toyofuku, Kyoko. Laboratory of Biophysics, School of Medicine, Teikyo University, Hachioji, Tokyo, 192-0395 Japan
    • Tabuchi, Toshihito. Faculty of Agriculture, Tamagawa University, 6-1-1 Tamagawa Gakuen, Machida, Tokyo, 194-8610 Japan
    • Shiratake, Katsuhiro. Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, 464-8601 Japan
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Plant and Cell Physiology, 2004, vol. 45, no. 8, p. 1032-1041. Oxford University Press
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:294941
    Summary
    Sorbitol is a major photosynthetic product and a major phloem-translocated component in Rosaceae (e.g. apple, pear, peach, and cherry). We isolated the three cDNAs, MdSOT3, MdSOT4, and MdSOT5 from apple (Malus domestica) source leaves, which are homologous to plant polyol transporters. Yeasts transformed with the MdSOTs took up sorbitol significantly. MdSOT3- and MdSOT5-dependent sorbitol uptake was strongly inhibited by xylitol and myo-inositol, but not or only weakly by mannitol and dulcitol. Apparent Km values of MdSOT3 and MdSOT5 for sorbitol were estimated to be 0.71mM and 3.2mM, respectively. The protonophore, carbonyl cyanide m-chlorophenylhydrazone (CCCP), strongly inhibited the sorbitol transport. MdSOT3 was expressed specifically in source leaves, whereas MdSOT4 and MdSOT5 were expressed in source leaves and also in some sink organs. MdSOT4 and MdSOT5 expressions were highest in flowers. Fruits showed no or only weak MdSOT expression. Although MdSOT4 and MdSOT5 were also expressed in immature leaves, MdSOT expressions increased with leaf maturation. In addition, in situ hybridization revealed that all MdSOTs were expressed to high levels in phloem of minor veins in source leaves. These results suggest that these MdSOTs are involved in sorbitol loading in Rosaceae