Cloning, Localization, and Expression Analysis of a New Tonoplast Monosaccharide Transporter from Vitis vinifera L |
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| Authors: | Lei Zeng Zeng Wang Alexander Vainstein Shangwu Chen Huiqin Ma |
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| Institution: | (1) Key Lab of Functional Dairy Science of Chinese Ministry of Education and Municipal Government of Beijing, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China;(2) College of Agriculture and Biotechnology, China Agricultural University, Beijing, China;(3) The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel; |
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| Abstract: | Tonoplast sugar transporters are important for sugar partitioning, immobilization, and accumulation during fruit development
and ripening. Here we report the cloning, localization, and functional analysis of one of these transporters in grape berries
(Vitis vinifera L.). This clone, named VvTMT1, encodes a 742-aa protein with a calculated molecular mass of 80.2 kDa. Predicted membrane topology and phylogenetic analysis
suggest that VvTMT1 belongs to the major facilitator superfamily of membrane carriers. Semiquantitative RT-PCR suggests that VvTMT1 is a sink-specific transporter, whose expression decreases with berry development. Heterologous expression of VvTMT1 in yeast can partially restore growth of the hxt-null strain in glucose and other monosaccharide media, indicating that VvTMT1 is a functional monosaccharide transporter.
Induction of VvTMT1-GFP fusion protein expression in transgenic yeast revealed its tonoplast localization. The subcellular
localization of VvTMT1 in plants was shown by immunogold labeling of grape berry mesocarp cells and VvTMT1-GFP transient expression
in tobacco epidermis cells. Based on the above analyses of VvTMT1, this is the first report of a functional tonoplast-localized
monosaccharide transporter in grapevine. |
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