Evidence for a novel route of wheat storage proteins to vacuoles.

Levanony, Hanna; Rubin, Regina; Altschuler, Yoram; Galili, Gad

doi:10.1083/jcb.119.5.1117

Cited by 251 publications

(216 citation statements)

References 36 publications

(59 reference statements)

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“…72 Microautophagy has been reported during plant senescence and development, but little is known about its role in plant cell homeostasis. 48,50,[73][74][75] It is possible that ATG5 is involved in a microautophagy-like or other novel mechanism that does not require ATG9 (Fig. 9).…”

Section: Discussionmentioning

confidence: 99%

“…Autophagy is blocked in rns2-2 atg9-4 and rns2-2 atg5-1 Some autophagy-like processes have been described that do not rely on the classical autophagy machinery. [48][49][50] To characterize the dependence of the rns2-2 constitutive autophagy phenotype on known core autophagy proteins, we analyzed autophagy in rns2-2 atg9-4 and rns2-2 atg5-1 double mutants. Seven-dold seedling roots were stained with MDC to detect autophagosomes and were visualized by confocal microscopy ( Fig.…”

Section: Atg8-labeled Autophagic Bodies Accumulate In An Rns2-2 Mutantmentioning

confidence: 99%

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Evidence for autophagy-dependent pathways of rRNA turnover inArabidopsis

et al. 2015

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Ribosomes account for a majority of the cell's RNA and much of its protein and represent a significant investment of cellular resources. The turnover and degradation of ribosomes has been proposed to play a role in homeostasis and during stress conditions. Mechanisms for the turnover of rRNA and ribosomal proteins have not been fully elucidated. We show here that the RNS2 ribonuclease and autophagy participate in RNA turnover in Arabidopsis thaliana under normal growth conditions. An increase in autophagosome formation was seen in an rns2-2 mutant, and this increase was dependent on the core autophagy genes ATG9 and ATG5. Autophagosomes and autophagic bodies in rns2-2 mutants contain RNA and ribosomes, suggesting that autophagy is activated as an attempt to compensate for loss of rRNA degradation. Total RNA accumulates in rns2-2, atg9-4, atg5-1, rns2-2 atg9-4, and rns2-2 atg5-1 mutants, suggesting a parallel role for autophagy and RNS2 in RNA turnover. rRNA accumulates in the vacuole in rns2-2 mutants. Vacuolar accumulation of rRNA was blocked by disrupting autophagy via an rns2-2 atg5-1 double mutant but not by an rns2-2 atg9-4 double mutant, indicating that ATG5 and ATG9 function differently in this process. Our results suggest that autophagy and RNS2 are both involved in homeostatic degradation of rRNA in the vacuole.

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Section: Discussionmentioning

confidence: 99%

Section: Atg8-labeled Autophagic Bodies Accumulate In An Rns2-2 Mutantmentioning

confidence: 99%

Evidence for autophagy-dependent pathways of rRNA turnover inArabidopsis

et al. 2015

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“…In wheat, however, the deposition of seed storage protein into protein bodies inside vacuoles does not involve transit through the Golgi complex. Instead, the storage proteins aggregate into protein bodies within the ER and are then transported as intact protein bodies to the vacuole by a novel route (Levanony et al, 1992). Retention of many of the ER proteins in the lumen of the ER has been attributed to the presence of an amino acid sequence (KDEL) at the carboxy terminus (Pelham, 1990).…”

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confidence: 99%

Accumulation of 15-Kilodalton Zein in Novel Protein Bodies in Transgenic Tobacco

et al. 1995

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Zeins, the seed storage proteins of maize, are a group of alcoholsoluble polypeptides of different molecular masses that share a similar amino acid composition but vary i n their sulfur amino acid composition. They are synthesized on the rough endoplasmic reticulum (ER) in the endosperm and are stored in ER-derived protein bodies. Our goal i s to balance the amino acid composition of the methionine-deficient forage legumes by expressing the sulfur amino acid-rich 15-kD zeins in their leaves. However, it is crucial to know whelher this protein would be stable i n nonseed tissues of transgenic plants. The major focus of this paper is to compare the accumulation pattern of the 15-kD zein protein with a vacuolar targeted seed protein, p-phaseolin, in nonseed tissues and to determine the basis for i t s stability/instability. We have introduced the 15-kD zein and bean p-phaseolin-coding sequences behind the 35s cauliflower mosaic virus promoter into tobacco (Nicofiana fabacum) and analyzed the protein's accumulation pattern in different tissues. Our results demonstrate that the 15-kD seed protein i s stable not only i n seeds but in all nonseed tissues tested, whereas the P-phaseolin protein accumulated only i n mid-and postmaturation seeds. Interestingly, zein accumulates in novel protein bodies both in the seeds and in nonseed tissues. We attribute the instability of the p-phaseolin protein i n nonseed tissues to the fact that it is targeted to protease-rich vacuoles. The stability of the 15-kD zein could be attributed to its retention i n the ER or to the proteaseresistant nature of the protein.Seed storage proteins constitute a potentially useful class of proteins for the improvement of forage crops if they can be made to accumulate in leaves. It is a fairly simple genetic engineering feat to introduce a seed protein-coding sequence behind a strong constitutive promoter into transgenic plants and ensure high rates of synthesis of the corresponding protein. However, stability of the protein in an alien environment is still not clearly defined and has to be treated on a case by case basis.Seed proteins are synthesized during seed development and accumulate in protein bodies. These proteins are then utilized by the emerging seedling during germination. The major seed protein in dicotyledonous plants are the saltsoluble globulins, which are stored in vacuole-derived protein bodies. Most monocot seed storage proteins are '

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“…The few examples of proteins that reach the vacuoles while bypassing the Golgi apparatus are ascribed to membrane proteins or to polypeptides that form insoluble aggregates (Levanony et al, 1992;Hara-Nishimura et al, 1998;Herman and Schmidt, 2004). Moreover, the direct transport of proteins from the ER to the vacuole can be adopted by cells in particular physiological situations such as seed germination (Chrispeels and Herman, 2000) or apoptosis (Hayashi et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the route that bypasses the Golgi system seems to be linked to the specific transport of proteins that form large aggregates (Herman and Schmidt, 2004;Herman, 2008). Cereal prolamins, when aggregated in the ER in large polymers, can also be transported directly from the ER to PSVs, apparently by autophagy (Levanony et al, 1992;Reyes et al, 2011). Moreover, many vacuolar enzymes are stored in ER-derived vesicles, which, under certain circumstances such as programmed cell death or seed germination, are directly fused with the vacuolar compartment (Hayashi et al, 2001;Rojo et al, 2003).…”

mentioning

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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Evidence for a novel route of wheat storage proteins to vacuoles.

Cited by 251 publications

References 36 publications

Evidence for autophagy-dependent pathways of rRNA turnover inArabidopsis

Evidence for autophagy-dependent pathways of rRNA turnover inArabidopsis

Accumulation of 15-Kilodalton Zein in Novel Protein Bodies in Transgenic Tobacco

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

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