What Is Moving in the Secretory Pathway of Plants?

Rojo, Enrique; Denecke, Jürgen

doi:10.1104/pp.108.124552

Cited by 71 publications

(72 citation statements)

References 99 publications

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“…The plant cell is the only one with two types of vacuoles (LVs and PSVs) having distinctive features (Frigerio et al, 2008;Rojo and Denecke, 2008). As a consequence, the secretory pathway to this organelle is much more complex in plants with respect to other organisms with vacuoles.…”

Section: Discussionmentioning

confidence: 99%

Traffic of Human α-Mannosidase in Plant Cells Suggests the Presence of a New Endoplasmic Reticulum-to-Vacuole Pathway without Involving the Golgi Complex

2013

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The transport of secretory proteins from the endoplasmic reticulum to the vacuole requires sorting signals as well as specific transport mechanisms. This work is focused on the transport in transgenic tobacco (Nicotiana tabacum) plants of a human a-mannosidase, MAN2B1, which is a lysosomal enzyme involved in the turnover of N-linked glycoproteins and can be used in enzyme replacement therapy. Although ubiquitously expressed, a-mannosidases are targeted to lysosomes or vacuoles through different mechanisms according to the organisms in which these proteins are produced. In tobacco cells, MAN2B1 reaches the vacuole even in the absence of mannose-6-phosphate receptors, which are responsible for its transport in animal cells. We report that MAN2B1 is targeted to the vacuole without passing through the Golgi complex. In addition, a vacuolar targeting signal that is recognized in plant cells is located in the MAN2B1 amino-terminal region. Indeed, when this amino-terminal domain is removed, the protein is retained in the endoplasmic reticulum. Moreover, when this domain is added to a plantsecreted protein, the resulting fusion protein is partially redirected to the vacuole. These results strongly suggest the existence in plants of a new type of vacuolar traffic that can be used by leaf cells to transport vacuolar proteins.

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Section: Discussionmentioning

confidence: 99%

Traffic of Human α-Mannosidase in Plant Cells Suggests the Presence of a New Endoplasmic Reticulum-to-Vacuole Pathway without Involving the Golgi Complex

2013

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“…We note that in plants there is no known pathway for proteins to localize in vacuoles after translation on cytosolic ribosomes (Marty, 1999;Vitale and Raikhel, 1999;Vitale and Hinz, 2005;Rojo and Denecke, 2008). In yeast (Saccharomyces cerevisiae) however, autophagylike mechanisms for cytoplasm to vacuole targeting have been described (Baba et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

“…For retention of proteins in other intracellular compartments, positive sorting information is also thought to be required, with ER signals also well characterized. However, soluble Golgi or endosomal compartment proteins have not been reported; thus their retention signals are not known (Rojo and Denecke, 2008). It was shown previously that overexpression of a secreted form of GFP results in its targeting to puncta identified as part of the vacuolar pathway.…”

Section: Discussionmentioning

confidence: 99%

“…Studies performed mostly in tobacco (Nicotiana tabacum) and Arabidopsis have established that protein sorting to vacuoles requires one of two types of cis-peptide signals, each of which interacts with a specific vacuolar sorting receptor (Vitale and Hinz, 2005;Hunter et al, 2007;Rojo and Denecke, 2008;Bottanelli et al, 2011), neither of which is found in MtENOD8-SP. For retention of proteins in other intracellular compartments, positive sorting information is also thought to be required, with ER signals also well characterized.…”

Section: Discussionmentioning

confidence: 99%

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Multiple Domains in MtENOD8 Protein Including the Signal Peptide Target It to The Symbiosome

et al. 2012

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Symbiotic nitrogen fixation occurs in nodules, specialized organs on the roots of legumes. Within nodules, host plant cells are infected with rhizobia that are encapsulated by a plant-derived membrane forming a novel organelle, the symbiosome. In Medicago truncatula, the symbiosome consists of the symbiosome membrane, a single rhizobium, and the soluble space between them, called the symbiosome space. The symbiosome space is enriched with plant-derived proteins, including the M. truncatula EARLY NODULIN8 (MtENOD8) protein. Here, we present evidence from green fluorescent protein (GFP) fusion experiments that the MtENOD8 protein contains at least three symbiosome targeting domains, including its N-terminal signal peptide (SP). When ectopically expressed in nonnodulated root tissue, the MtENOD8 SP delivers GFP to the vacuole. During the course of nodulation, there is a nodule-specific redirection of MtENOD8-SP-GFP from the vacuole to punctate intermediates and subsequently to symbiosomes, with redirection of MtENOD8-SP-GFP from the vacuole to punctate intermediates preceding intracellular rhizobial infection. Experiments with M. truncatula mutants having defects in rhizobial infection and symbiosome development demonstrated that the MtNIP/LATD gene is required for redirection of the MtENOD8-SP-GFP from the vacuoles to punctate intermediates in nodules. Our evidence shows that MtENOD8 has evolved redundant targeting sequences for symbiosome targeting and that intracellular localization of ectopically expressed MtENOD8-SP-GFP is useful as a marker for monitoring the extent of development in mutant nodules.

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“…This is followed by the Held et al (2008) Update on the prowess of what combinations of fluorescence-based microscope and live cell imaging can achieve for spatial and functional assignments for specific molecules within the entire endomembrane system. The Rojo and Denecke (2008) and Robinson et al (2008) Updates examine the most recently defined players in the secretory and endosomal pathways and how these may be used to interpret, reconcile, or extend prior results. These provide good roadmaps, especially for researchers whose work would benefit from a membrane trafficking perspective.…”

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confidence: 99%