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  • Publication
    Métadonnées seulement
    Two glycosylated vacuolar GFPs are new markers for ER-to-vacuole sorting
    (2013)
    Stigliano, Egidio
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    Faraco, Marianna
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    Montefusco, Anna
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    Dalessandro, Giuseppe
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    Piro, Gabriella
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    Di Sansebastiano, Gian-Pietro
    Vacuolar Sorting Determinants (VSDs) have been extensively studied in plants but the mechanisms for the accumulation of storage proteins in somatic tissues are not yet fully understood. In this work we used two mutated versions of well-documented vacuolar fluorescent reporters, a GFP fusion in frame with the C-terminal VSD of tobacco chitinase (GFPChi) and an N-terminal fusion in frame with the sequence-specific VSD of the barley cysteine protease aleurain (AleuGFP). The GFP sequence was mutated to present an N-glycosylation site at the amino-acid position 133. The reporters were transiently expressed in Nicotiana tabacum protoplasts and agroinfiltrated in Nicotiana benthamiana leaves and their distribution was identical to that of the non-glycosylated versions. With the glycosylated GFPs we could highlight a differential ENDO-H sensitivity and therefore differential glycan modifications. This finding suggests two different and independent routes to the vacuole for the two reporters. BFA also had a differential effect on the two markers and further, inhibition of COPII trafficking by a specific dominant-negative mutant (NtSar1h74l) confirmed that GFPChi transport from the ER to the vacuole is not fully dependent on the Golgi apparatus.
  • Publication
    Accès libre
    Expression of a glycosylated GFP as a bivalent reporter in exocytosis
    (2010)
    Paris, Nadine
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    Saint-Jean, Bruno
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    Faraco, Marianna
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    Krzeszowiec, Weronika
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    Dalessandro, Giuseppe
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    Di Sansebastiano, Gian Pietro
    The complex-type N-linked glycans of plants differ markedly in structure from those of animals. Like those of insects and mollusks they lack terminal sialic acid(s) and may contain an α-(1,3)-fucose (Fuc) linked to the proximal GlcNAc residue and/or a β-(1,2)-xylose (Xyl) residue attached to the proximal mannose (Man) of the glycan core. N-glycosylated GFPs were used in previous studies showing their effective use to report on membrane traffic between the ER and the Golgi apparatus in plant cells. In all these cases glycosylated tags were added at the GFP termini. Because of the position of the tag and depending on the sorting and accumulation site of these modified GFP, there is always a risk of processing and degradation, and this protein design cannot be considered ideal. Here, we describe the development of three different GFPs in which the glycosylation site is internally localized at positions 80, 133, or 172 in the internal sequence. The best glycosylation site was at position 133. This glycosylated GFPgl133 appears to be protected from undesired processing of the glycosylation site and represents a bivalent reporter for biochemical and microscopic studies. After experimental validation, we can conclude that amino acid 133 is an effective glycosylation site and that the GFPgl133 is a powerful tool for in vivo investigations in plant cell biology.
  • Publication
    Accès libre
    Vacuolar system distribution in Arabidopsis tissues, visualized using GFP fusion proteins
    (2003-06-01)
    Flückiger, Ricardo
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    De Caroli, Monica
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    Piro, Gabriella
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    Dalessandro, Giuseppe
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    ;
    Di Sansebastiano, Gian-Pietro
    Green fluorescent protein (GFP) allows the direct visualization of gene expression and the subcellular localization of fusion proteins in living cells. The localization of different GFP fusion proteins in the secretory system was studied in stably transformed Arabidopsis plants cv. Wassilewskaja. Secreted GFP (SGFP) and GFP retained in the ER (GFP-KDEL) confirmed patterns already known, but two vacuolar GFPs (GFP-Chi and Aleu-GFP) labelled the Arabidopsis vacuolar system for the first time, the organization of which appears to depend on cell differentiation. GFP stability in the vacuoles may depend on pH or degradation, but these vacuolar markers can, nevertheless, be used as a tool for physiological studies making these plants suitable for mutagenesis and gene-tagging experiments.
  • Publication
    Métadonnées seulement
    Regeneration of a lytic central vacuole and of neutral peripheral vacuoles can be visualized by green fluorescent proteins targeted to either type of vacuoles
    (2001)
    Di Sansebastiano, Gian Pietro
    ;
    Paris, Nadine
    ;
    ;
    Protein trafficking to two different types of vacuoles was investigated in tobacco (Nicotiana tabacum cv SR1) mesophyll protoplasts using two different vacuolar green fluorescent proteins (GFPs). One GFP is targeted to a pH-neutral vacuole by the C-terminal vacuolar sorting determinant of tobacco chitinase A, whereas the other GFP is targeted to an acidic lytic vacuole by the N-terminal propeptide of barley aleurain, which contains a sequence-specific vacuolar sorting determinant. The trafficking and final accumulation in the central vacuole (CV) or in smaller peripheral vacuoles differed for the two reporter proteins, depending on the cell type. Within 2 d, evacuolated (mini-) protoplasts regenerate a large CV. Expression of the two vacuolar GFPs in miniprotoplasts indicated that the newly formed CV was a lytic vacuole, whereas neutral vacuoles always remained peripheral. Only later, once the regeneration of the CV was completed, the content of peripheral storage vacuoles could be seen to appear in the CV of a third of the cells, apparently by heterotypic fusion.