Protein bodies of mung bean cotyledons as autophagic organelles

Wilden, Willem Van der; Herman, Eliot M.; Chrispeels, Maarten J.

doi:10.1073/pnas.77.1.428

Cited by 138 publications

(53 citation statements)

References 19 publications

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“…It is worth noting in this context that protein bodies are part of the vacuolar/lysosomal compartment of plant cells. Recent evidence shows that protein bodies are derived from vacuoles during seed maturation (5,6,27) and that they contain numerous acid hydrolases (14,17,20,26). Protein bodies therefore have an enzymic complement and function similar to that of the central vacuole of plant cells or the lysosomes of animal cells.…”

Section: Discussionmentioning

confidence: 99%

Assembly of storage protein oligomers in the endoplasmic reticulum and processing of the polypeptides in the protein bodies of developing pea cotyledons

Chrispeels¹,

Higgins²,

Spencer³

1982

The Journal of Cell Biology

175

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Cotyledons of developing pea seeds (Pisurn sativum L.) were labeled with radioactive amino acids and glucosamine, and extracts were prepared and separated into fractions rich in endoplasmic reticulum (ER) or protein bodies . The time-course of synthesis of the polypeptides of legumin and vicilin and the site of their assembly into protein oligomers were studied using immunoaffinity gels and sucrose density gradients. When cotyledons were pulselabeled (1-2 h), newly synthesized legumin was present in polypeptides with Mr 60,000-65,000, and newly synthesized vicilin was present as a series of polypeptides with Mr 75,000, 70,000, 50,000, and 49,000. These radioactive polypeptides were found primarily in the ER (Chrispeels et al ., 1982, /. Cell BioL, 93 :5-14) . During a subsequent chase period, newly synthesized reserve proteins were initially present in the protein bodies in the above-named polypeptides . Between 1 and 20 h later, radioactive legumin subunits (M r 40,000 and 19,000) and smaller vicilin polypeptides (Mr 34,000, 30,000, 25,000, 18,000, 14,000, 13,000, and 12,000) appeared in the protein bodies . The appearance of these labeled polypeptides in the protein bodies was not the result of a slow transport from the ER (or cytoplasm) .Newly synthesized legumin and vicilin polypeptides were assembled into oligomers of 85 and 7S, respectively, in the ER . They appeared in the protein bodies in these oligomeric forms before the appearance of the smaller polypeptides (M r <49,000) . These results indicate that the smaller vicilin polypeptides (M r <49,000) arise by delayed posttranslational processing of some or all of the larger vicilin polypeptides . The precursors of legumin are completely processed in the protein bodies 2-3 h after their synthesis. The processing of the vicilin precursors is much slower (6-20 h) and only a fraction of the precursor molecules are processed . As a result both large (M r >49,000) and small polypeptides of vicilin accumulate in the protein bodies, whereas legumin accumulates only as polypeptides of Mr 40,000 and 19,000 .The large parenchymal cells of the cotyledons of pea (Pisum sativum L.) seeds contain 20-30% protein on a dry weight basis. The reserve proteins vicilin and legumin make up 70% of this protein. These reserve proteins are localized in protein bodies, which are spherical organelles measuring 1-3 gm in diameter consisting of an amorphous protein matrix surrounded by a limiting membrane. In mature seeds, legumin is a 12S protein (Mr 360,000) that consists of six acidic (Mr 40,000) and six basic (Mr 20,000) subunits, linked together in pairs by disulfide bridges (11). When legumin is fractionated by SDS PAGE, heterogeneity is found in both the acidic and basic subunits with three to five polypeptides in each molecular weight class .306

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Section: Discussionmentioning

confidence: 99%

Assembly of storage protein oligomers in the endoplasmic reticulum and processing of the polypeptides in the protein bodies of developing pea cotyledons

Chrispeels¹,

Higgins²,

Spencer³

1982

The Journal of Cell Biology

175

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“…The hypothesis that PSVs have an ontogenetic relationship to the central vacuole has a long history (Hara and Matsubara, 1980;Van der Wilden et al, 1980;Melroy and Herman, 1991;Olbrich et al, 2007), but the general mechanism of the PSV-to-LV transformation Figure 9. Schematic diagram illustrating the different pathways involved in the transformation of PSVs into LVs in different types of root cells during seed germination and early root development.…”

Section: Cryofixation and Freeze-substitution Methods Are Important Fmentioning

confidence: 99%

“…Most likely, this sequence of events is designed to allow for the development of the vascular system before the amino acids are mobilized in the cotyledons and sent to the embryo axis cells (Tiedemann et al, 2001). During mobilization of the reserves, the PSVs become more acidic and acquire hydrolytic enzymes, and these physiological changes are accompanied by major changes in PSV structure (Ashton, 1976;Van der Wilden et al, 1980;Bethke et al, 1998;Tiedemann et al, 2000Tiedemann et al, , 2001Jiang et al, 2001, Saito et al, 2002He et al, 2007;Wang et al, 2007).…”

mentioning

confidence: 99%

Protein Storage Vacuoles Are Transformed into Lytic Vacuoles in Root Meristematic Cells of Germinating Seedlings by Multiple, Cell Type-Specific Mechanisms

Zheng

Staehelin

2011

Plant Physiology

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We have investigated the structural events associated with vacuole biogenesis in root tip cells of tobacco (Nicotiana tabacum) seedlings preserved by high-pressure freezing and freeze-substitution techniques. Our micrographs demonstrate that the lytic vacuoles (LVs) of root tip cells are derived from protein storage vacuoles (PSVs) by cell type-specific sets of transformation events. Analysis of the vacuole transformation pathways has been aided by the phytin-dependent black osmium staining of PSV luminal contents. In epidermal and outer cortex cells, the central LVs are formed by a process involving PSV fusion, storage protein degradation, and the gradual replacement of the PSV marker protein a-tonoplast intrinsic protein (TIP) with the LV marker protein g-TIP. In contrast, in the inner cortex and vascular cylinder cells, the transformation events are more complex. During mobilization of the stored molecules, the PSV membranes collapse osmotically upon themselves, thereby squeezing the vacuolar contents into the remaining bulging vacuolar regions. The collapsed PSV membranes then differentiate into two domains: (1) vacuole "reinflation" domains that produce pre-LVs, and (2) multilamellar autophagosomal domains that are later engulfed by the pre-LVs. The multilamellar autophagosomal domains appear to originate from concentric sheets of PSV membranes that create compartments within which the cytoplasm begins to break down. Engulfment of the multilamellar autophagic vacuoles by the pre-LVs gives rise to the mature LVs. During pre-LV formation, the PSV marker a-TIP disappears and is replaced by the LV marker g-TIP. These findings demonstrate that the central LVs of root cells arise from PSVs via cell type-specific transformation pathways.

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“…In seeds, for example, protein storage vacuoles are formed during maturation while the proteins are degraded by the time of seed germination. 40 Data of Van der Wilden et al 41 and Herman et al 42 suggested that protein bodies enclose what seem to be autophagic vesicles. These vesicles carry acid hydrolases, including carboxypeptidase.…”

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confidence: 99%