Induction of Specialized Compartments from the ER

Hara‐Nishimura, Ikuko; Shimada, Tomoo

doi:10.1007/7089_067

Cited by 2 publications

(1 citation statement)

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“…Another exception, although only of temporary nature, are the PAC (precursor-accumulating) vesicles seen in maturing pumpkin ( Cucurbita maxima ) and castor bean ( Ricinus communis ) seeds. These are derived from the ER and contain aggregates of the pro-forms of 11S globulins and 2S albumin (Hara-Nishimura and Shimada, 2006). On their way to the PSV, PAC vesicles receive a contribution from the Golgi apparatus, as they also contain complex glycans (Hara-Nishimura et al ., 1998; Jiang and Sun, 2002).…”

Section: Discussionmentioning

confidence: 99%

Successful transport to the vacuole of heterologously expressed mung bean 8S globulin occurs in seed but not in vegetative tissues

Wang

Shen

Cai

et al. 2013

Journal of Experimental Botany

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This study investigated the subcellular location of mung bean (Vigna radiata) 8S globulin in transient expression systems as well as in tobacco (Nicotiana tabacum) BY-2 cells and different tissues from a transgenic Arabidopsis (Arabidopsis thaliana) line stably expressing this storage globulin. When transiently expressed in protoplasts from both BY-2 cells and Arabidopsis suspension cultured cells, the 8S globulin located to structures that were neither Golgi nor pre-vacuolar compartments (PVCs). Immunogold electron microscopy of the transgenics reveals the 8S globulin-positive structures to be small, spherical, ribosome-covered endoplasmic reticulum (ER)-derived bodies. In BY-2 cells and all vegetative cells, the 8S globulin was present as a pro-form. However, in Arabidopsis embryos, with the onset of endogenous storage protein synthesis, the 8S globulin exited the ER and passed through the PVC to the protein storage vacuole where it was processed to its smaller mature form. These results clearly demonstrated that, when taken out of context and expressed in vegetative cells, the mung bean 8S storage globulin cannot exit the ER, and indicate that natural targeting of storage proteins to the vacuole should be better studied in the maturing seed.

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Section: Discussionmentioning

confidence: 99%

Successful transport to the vacuole of heterologously expressed mung bean 8S globulin occurs in seed but not in vegetative tissues

Wang

Shen

Cai

et al. 2013

Journal of Experimental Botany

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Receptor-mediated transport of vacuolar proteins: a critical analysis and a new model

Robinson

Pimpl

2013

Protoplasma

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In this article we challenge the widely accepted view that receptors for soluble vacuolar proteins (VSRs) bind to their ligands at the trans-Golgi network (TGN) and transport this cargo via clathrin-coated vesicles (CCV) to a multivesicular prevacuolar compartment. This notion, which we term the "classical model" for vacuolar protein sorting, further assumes that low pH in the prevacuolar compartment causes VSR-ligand dissociation, resulting in a retromer-mediated retrieval of the VSRs to the TGN. We have carefully evaluated the literature with respect to morphology and function of the compartments involved, localization of key components of the sorting machinery, and conclude that there is little direct evidence in its favour. Firstly, unlike mammalian cells where the sorting receptor for lysosomal hydrolases recognizes its ligand in the TGN, the available data suggests that in plants VSRs interact with vacuolar cargo ligands already in the endoplasmic reticulum. Secondly, the evidence supporting the packaging of VSR-ligand complexes into CCV at the TGN is not conclusive. Thirdly, the prevacuolar compartment appears to have a pH unsuitable for VSR-ligand dissociation and lacks the retromer core and the sorting nexins needed for VSR recycling. We present an alternative model for protein sorting in the TGN that draws attention to the much overlooked role of Ca(2+) in VSR-ligand interactions and which may possibly also be a factor in the sequestration of secretory proteins.

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Induction of Specialized Compartments from the ER

Cited by 2 publications

References 50 publications

Successful transport to the vacuole of heterologously expressed mung bean 8S globulin occurs in seed but not in vegetative tissues

Successful transport to the vacuole of heterologously expressed mung bean 8S globulin occurs in seed but not in vegetative tissues

Receptor-mediated transport of vacuolar proteins: a critical analysis and a new model

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