Localization of Green Fluorescent Protein Fusions with the Seven Arabidopsis Vacuolar Sorting Receptors to Prevacuolar Compartments in Tobacco BY2 Cells1(W)(OA) (original) (raw)
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Plant Physiology, 2006
We have previously demonstrated that vacuolar sorting receptor (VSR) proteins are concentrated on prevacuolar compartments (PVCs) in plant cells. PVCs in tobacco (Nicotiana tabacum) BY-2 cells are multivesicular bodies (MVBs) as defined by VSR proteins and the BP-80 reporter, where the transmembrane domain (TMD) and cytoplasmic tail (CT) sequences of BP-80 are sufficient and specific for correct targeting of the reporter to PVCs. The genome of Arabidopsis (Arabidopsis thaliana) contains seven VSR proteins, but little is known about their individual subcellular localization and function. Here, we study the subcellular localization of the seven Arabidopsis VSR proteins (AtVSR1-7) based on the previously proven hypothesis that the TMD and CT sequences correctly target individual VSR to its final destination in transgenic tobacco BY-2 cells. Toward this goal, we have generated seven chimeric constructs containing signal peptide (sp) linked to green fluorescent protein (GFP) and TMD/CT sequences (sp-GFP-TMD/CT) of the seven individual AtVSR. Transgenic tobacco BY-2 cell lines expressing these seven sp-GFP-TMD-CT fusions all exhibited typical punctate signals colocalizing with VSR proteins by confocal immunofluorescence. In addition, wortmannin caused the GFP-marked prevacuolar organelles to form small vacuoles, and VSR antibodies labeled these enlarged MVBs in transgenic BY-2 cells. Wortmannin also caused VSR-marked PVCs to vacuolate in other cell types, including Arabidopsis, rice (Oryza sativa), pea (Pisum sativum), and mung bean (Vigna radiata). Therefore, the seven AtVSRs are localized to MVBs in tobacco BY-2 cells, and wortmannin-induced vacuolation of PVCs is a general response in plants.
We have previously demonstrated that vacuolar sorting receptor (VSR) proteins are concentrated on prevacuolar compartments (PVCs) in plant cells. PVCs in tobacco (Nicotiana tabacum) BY-2 cells are multivesicular bodies (MVBs) as defined by VSR proteins and the BP-80 reporter, where the transmembrane domain (TMD) and cytoplasmic tail (CT) sequences of BP-80 are sufficient and specific for correct targeting of the reporter to PVCs. The genome of Arabidopsis thaliana contains seven VSR proteins, but little is known about their individual subcellular localization and function. Here we study the subcellular localization of the seven Arabidopsis VSR proteins (AtVSR1-7) based on previously proved hypothesis that the TMD and CT sequences correctly target individual VSR to its final destination in transgenic tobacco BY-2 cells. Toward this goal, we have generated seven chimeric constructs containing signal peptide (sp) linked to GFP (green fluorescent protein) and TMD/CT sequences (sp-GFP-TMD/CT) of the seven individual AtVSR. Transgenic tobacco BY-2 cell lines expressing these seven sp-GFP-TMD-CT fusions all exhibited typical punctate signals colocalizing with VSR proteins by confocal immunofluorescence. In addition, wortmannin caused the GFP-marked prevacuolar organelles to form small vacuoles and VSR antibodies labeled these enlarged MVBs in transgenic BY-2 cells. Wortmannin also caused VSR-marked PVCs to vacuolate in other cell types including Arabidopsis, rice, pea, and mungbean. Therefore, the seven AtVSRs are localized to MVBs in tobacco BY-2 cells and wortmannin-induced vacuolation of PVCs is a general response in plants. www.plant.org on January 12, 2015 -Published by www.plantphysiol.org Downloaded from
Protein Targeting to the Vacuole in Plant Cells
Plant Physiology, 1993
Bednarek SY, Raikhel NV (1991) The barley lectin carboxyl-termi-na1 propeptide is a vacuolar sorting determinant in plants. Plant Cell3 1195-1206 Bednarek SY, Raikhel NV (1992) Intracellular trafficking of secretory proteins. Plant Mo1 Biol 20: 133-150 Bednarek SY, Wilkins TA, Dombrowski JE, Raikhel NV (1990) A carboxyl-terminal propeptide is necessary for proper sorting of barley lectin to vacuoles of tobacco. Plant Cell 2 1145-1155 Braun M, Waheed A, von Figura K (1989) Lysosomal acid phos
Molecular cloning and further characterization of a probable plant vacuolar sorting receptor
Plant Physiology, 1997
(Pisum safivum) clathrin-coated vesicles (CCVs) that binds with high affinity to vacuole-targeting determinants containing asparagine-proline-isoleucine-arginine. Here we present results from cDNA cloning and studies of its intracellular localization. Its sequence and sequences of homologs from Arabidopsis, rice (Oryza safiva), and maize (Zea mays) define a nove1 family of proteins unique to plants that is highly conserved in both monocotyledons and dicotyledons. l h e BP-80 protein is present in dilated ends of Colgi cisternae and in "prevacuoles," which are small vacuoles separate from but capable of fusing with lytic vacuoles. Its cytoplasmic tail contains a Tyr-X-X-hydrophobic residue motif associated with transmembrane proteins incorporated into CCVs. When transiently expressed in tobacco (Nicotiana tabacum) suspensionculture protoplasts, a truncated form lacking transmembrane and cytoplasmic domains was secreted. These results, coupled with previous studies of ligand-binding specificity and pH dependence, strongly support our hypothesis that BP-80 is a vacuolar sorting receptor that trafficks in CCVs between Colgi and a newly described prevacuolar compartment.
Wortmannin induces homotypic fusion of plant prevacuolar compartments
Journal of Experimental Botany, 2009
Wortmannin, a specific inhibitor of phosphatidyl-inositol 3-kinase, is a useful tool for studying protein trafficking and identifying organelles in the plant secretory and endocytic pathways. It has recently been demonstrated that wortmannin at 16.5 mM or 33 mM caused the prevacuolar compartments (PVCs), identified as multivesicular bodies (MVBs) by their enrichment in vacuolar sorting receptor (VSRs) proteins and the BP-80 reporter, to form small vacuoles rapidly. However, the source(s) of the membrane needed for the rapid enlargement of PVCs/MVBs has been unclear. Using both confocal immunofluorescence and immunogold EM with high pressure freeze substitution of plant samples, it has been demonstrated here that wortmannin induces homotypic fusions of PVCs/MVBs thus providing an explanation for the demand for extra membrane. In addition, possible wortmannin-induced fusions between the trans-Golgi network (TGN) and PVC, as well as between the small internal vesicles and PVC membrane, were also observed and they may also contribute to the membranes needed for PVC enlargement. In contrast to mammalian cells and yeast, wortmannin-induced fusion of PVCs appears to be unique to plants.
The Journal of cell biology, 1995
Vacuolar matrix proteins in plant cells are sorted from the secretory pathway to the vacuoles at the Golgi apparatus. Previously, we reported that the NH2-terminal propeptide (NTPP) of the sporamin precursor and the COOH-terminal propeptide (CTPP) of the barley lectin precursor contain information for vacuolar sorting. To analyze whether these propeptides are interchangeable, we expressed constructs consisting of wild-type or mutated NTPP with the mature part of barley lectin and sporamin with CTPP and mutated NTPP in tobacco BY-2 cells. The vacuolar localization of these constructs indicated that the signals were interchangeable. We next analyzed the effect of wortmannin, a specific inhibitor of mammalian phosphatidylinositol (PI) 3-kinase on vacuolar delivery by NTPP and CTPP in tobacco cells. Pulse-chase analysis indicated that 33 microM wortmannin caused almost complete inhibition of CTPP-mediated transport to the vacuoles, while NTPP-mediated transport displayed almost no sensi...
Demonstration in Yeast of the Function of BP-80, a Putative Plant Vacuolar Sorting Receptor
THE PLANT CELL ONLINE, 2001
BP-80, later renamed VSR PS-1 , is a putative receptor involved in sorting proteins such as proaleurain to the lytic vacuole, with its N-terminal domain recognizing the vacuolar sorting determinant. Although all VSR PS-1 characteristics and in vitro binding properties described so far favored its receptor function, this function remained to be demonstrated. Here, we used green fluorescent protein (GFP) as a reporter in a yeast mutant strain defective for its own vacuolar receptor, Vps10p. By expressing VSR PS-1 together with GFP fused to the vacuolar sorting determinant of petunia proaleurain, we were able to efficiently redirect the reporter to the yeast vacuole. VSR PS-1 is ineffective on GFP either alone or when fused with another type of plant vacuolar sorting determinant from a chitinase. The plant VSR PS-1 therefore interacts specifically with the proaleurain vacuolar sorting determinant in vivo, and this interaction leads to the transport of the reporter protein through the yeast secretory pathway to the vacuole. This finding demonstrates VSR PS-1 receptor function but also emphasizes the differences in the spectrum of ligands between Vps10p and its plant equivalent.
Propeptide of a precursor to a plant vacuolar protein required for vacuolar targeting
Proceedings of the National Academy of Sciences, 1991
Sporamin is a protein without glycans that accumulates in large quantities in the vacuoles of the tuberous root of the sweet potato. It is synthesized as a prepro precursor with an N-terminal extension composed of a 21-amino-acid signal peptide and a 16-amino-acid propeptide. A total of 48 base pairs, corresponding to the nucleotide sequence that encodes the propeptide, was deleted from a cDNA clone for sporamin. This delta pro mutant sequence, as well as the sequence of the wild-type sporamin cDNA, was placed downstream from the promoter of the 35S transcript from cauliflower mosaic virus and introduced into the genome of suspension-cultured tobacco cells by Agrobacterium-mediated transformation. In contrast to the vacuolar localization of sporamin in cells that expressed the wild-type precursor, sporamin was secreted into the culture medium from cells in which the delta pro precursor was expressed. The secreted form of sporamin was shorter by two amino acids at its N terminus than...
Molecular Characterization of Plant Prevacuolar and Endosomal Compartments
Journal of Integrative Plant Biology, 2007
Prevacuolar compartments (PVCs) and endosomal compartments are membrane-bound organelles mediating protein traffic to vacuoles in the secretory and endocytic pathways of plant cells. Over the years, great progress has been made towards our understanding in these two compartments in plant cells. In this review, we will summarize our contributions toward the identification and characterization of plant prevacuolar and endosomal compartments. Our studies will serve as important steps in future molecular characterization of PVC biogenesis and PVC-mediated protein trafficking in plant cells.