A vacuolar iron transporter in tulip, TgVit1, is responsible for blue coloration in petal cells through iron accumulation |
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Authors: | Kazumi Momonoi Kumi Yoshida Shoji Mano Hideyuki Takahashi Chihiro Nakamori Kazuaki Shoji Akira Nitta Mikio Nishimura |
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Institution: | Graduate School of Information Science, Nagoya University, Nagoya 464-8601, Japan;, Horticultural Research Institute, Toyama Prefectural Agricultural, Forestry and Fisheries Research Center, Tonami 939-1327, Japan;, Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan;, Department of Basic Biology, School of Life Science, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan;, and Agricultural Research Institute, Toyama Prefectural Agricultural, Forestry and Fisheries Research Center, Toyama 939-8153, Japan |
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Abstract: | Blue color in flowers is due mainly to anthocyanins, and a considerable part of blue coloration can be attributed to metal-complexed anthocyanins. However, the mechanism of metal ion transport into vacuoles and subsequent flower color development has yet to be fully explored. Previously, we studied the mechanism of blue color development specifically at the bottom of the inner perianth in purple tulip petals of Tulipa gesneriana cv. Murasakizuisho. We found that differences in iron content were associated with the development of blue- and purple-colored cells. Here, we identify a vacuolar iron transporter in T. gesneriana ( TgVit1 ), and characterize the localization and function of this transporter protein in tulip petals. The amino acid sequence of TgVit1 is 85% similar that of the Arabidopsis thaliana vacuolar iron transporter AtVIT1, and also showed similarity to the AtVIT1 homolog in yeast, Ca2+-sensitive cross-complementer 1 (CCC1). The gene TgVit1 was expressed exclusively in blue-colored epidermal cells, and protein levels increased with increasing mRNA expression and blue coloration. Transient expression experiments revealed that TgVit1 localizes to the vacuolar membrane, and is responsible for the development of the blue color in purple cells. Expression of TgVit1 in yeast rescued the growth defect of ccc1 mutant cells in the presence of high concentrations of FeSO4. Our results indicate that TgVit1 plays an essential role in blue coloration as a vacuolar iron transporter in tulip petals. These results suggest a new role for involvement of a vacuolar iron transporter in blue flower color development. |
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Keywords: | TgVit1 Tulipa gesneriana vacuolar iron transporter blue flower coloration metal-complex anthocyanin |
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