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A complex and mobile structure forms a distinct subregion within the continuous vacuolar membrane in young cotyledons of Arabidopsis
Author(s) -
Saito Chieko,
Ueda Takashi,
Abe Hiroshi,
Wada Yoh,
Kuroiwa Tsuneyoshi,
Hisada Akiko,
Furuya Masaki,
Nakano Akihiko
Publication year - 2002
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.0960-7412.2001.01189.x
Subject(s) - vacuole , biology , arabidopsis , organelle , membrane , arabidopsis thaliana , microbiology and biotechnology , biophysics , cytoplasm , plant cell , green fluorescent protein , fluorescence microscope , electron microscope , protoplast , aquaporin , fluorescence , biochemistry , gene , physics , quantum mechanics , mutant , optics
Summary The plant vacuole is a multifunctional organelle which is essential for growth and development. To visualize the dynamics of plant vacuolar membranes, γ‐TIP (tonoplast intrinsic protein) was fused to GFP and expressed in Arabidopsis thaliana . The marker molecule was targeted to the vacuolar membranes in most tissues, as expected. In rapidly expanding cells, some additional spherical structures were often observed within the lumen of vacuoles, which emitted strong fluorescence. To confirm their normal presence, we examined wild‐type Arabidopsis cotyledons by transmission electron microscopy. The metal‐contact rapid‐freezing method revealed that the vacuolar lumen of epidermal cells contained many cytoplasmic projections, which often formed spherical structures (1–3 µm diameter) consisting of double membranes. Thus we concluded that these structures are authentic and named them ‘bulbs’. Three‐dimensional reconstruction from serial electron microscopic images demonstrates that bulbs are very intricately folded, but are continuous with the limiting vacuolar membrane. The fluorescence intensity of bulbs is about threefold higher than that of vacuolar membrane. GFP‐AtRab75c, another marker of the vacuole, did not give fluorescent signals of bulbs in transgenic plants, but the existence of bulbs was still confirmed by electron microscopy. These results suggest that bulbs define a subregion in the continuous vacuolar membrane, where some proteins are concentrated and others segregated.

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