Targeting of Proteins to Endoplasmic Reticulum-Derived Compartments in Plants. The Importance of RNA Localization

Crofts, Andrew J.; Washida, Haruhiko; Okita, Thomas W.; Ogawa, Masahiro; Kumamaru, Toshihiro; Satoh, Hiroyuki

doi:10.1104/pp.104.048934

Cited by 62 publications

(55 citation statements)

References 34 publications

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“…These experiments indicate that the patterns of localization of the Sad1 and Sad2 mRNAs in the cytoplasm are distinct and rarely overlap, suggesting that the translation of these two mRNA species into proteins is unlikely to be spatially coordinated. A few examples of targeting of transcripts to specific parts of the cytoplasm in plant cells have been reported, including transcripts for expansins and seed storage proteins (Choi et al, 2000;Okita and Choi, 2002;Crofts et al, 2004;Washida et al, 2004). Avenacins accumulate in the cell vacuole (Mylona et al, 2008), but the route by which pathway intermediates are transported from the ER to this final destination is unknown.…”

Section: Online) Sad1mentioning

confidence: 99%

Cell Type–Specific Chromatin Decondensation of a Metabolic Gene Cluster in Oats

et al. 2009

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Transcription-related chromatin decondensation has been studied in mammals for clusters of structurally and/or functionally related genes that are coordinately regulated (e.g., the homeobox locus in mice and the major histocompatability complex locus in humans). Plant genes have generally been considered to be randomly distributed throughout the genome, although several examples of metabolic gene clusters for synthesis of plant defense compounds have recently been discovered. Clustering provides for genetic linkage of genes that together confer a selective advantage and may also facilitate coordinate regulation of gene expression by enabling localized changes in chromatin structure. Here, we use cytological methods to investigate components of a metabolic gene cluster for synthesis of developmentally regulated defense compounds (avenacins) in diploid oat (Avena strigosa). Our experiments reveal that expression of the avenacin gene cluster is associated with cell type-specific chromatin decondensation, providing new insights into regulation of gene clusters in plants. Importantly, chromatin decondensation could be visualized not only at the large-scale level but down to the single gene level. We further show that the avenacin and sterol pathways are likely to be inversely regulated at the level of transcription.

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Section: Online) Sad1mentioning

confidence: 99%

Cell Type–Specific Chromatin Decondensation of a Metabolic Gene Cluster in Oats

et al. 2009

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“…Some rice prolamins contain the characteristic ABC sequences described above; however, unlike monomeric 2S albumins, the ABC-containing prolamins are stored in the form of polymers or aggregates in spherical intracisternal inclusion granules, referred to as type I protein bodies (PB-I), within the endoplasmic reticulum (ER) lumen (Mitsukawa et al, 1999;Muench et al, 1999). Recent studies have reported that the mRNAs of these prolamins associate with protein body ER, whereas the mRNAs of glutelins associate with cisternal ER (Crofts et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

The Critical Role of Disulfide Bond Formation in Protein Sorting in the Endosperm of Rice

et al. 2005

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Many seed storage proteins, including monomeric 2S albumin and polymeric prolamin, contain conserved sequences in three separate regions, termed A, B, and C, which contain the consensus motifs LxxC, CCxQL, and PxxC, respectively. Protein-sorting mechanisms in rice (Oryza sativa) endosperm were studied with a green fluorescent protein (GFP) fused to different segments of rice a-globulin, a monomeric, ABC-containing storage protein. The whole ABC region together with GFP was efficiently transported to protein storage vacuoles (type II protein bodies [PB-II]) in the endosperm cells and sequestered in the matrix that surrounds the crystalloids. Peptide Gln-23 to Ser-43 in the A region was sufficient to guide GFP to PB-II. However, GFP fused with the AB or B region accumulated in prolamin protein bodies. Substitution mutations in the CCxQL motif in the B region significantly altered protein localization in the endosperm cells. Furthermore, protein extracts containing these substituted proteins had increased amounts of the endoplasmic reticulum (ER) chaperons BiP (for binding protein), protein disulfide isomerase, and calnexin as a part of protein complexes that were insoluble in a detergent buffer. These results suggest that the ER chaperons and disulfide bonds formed at the dicysteine residues in CCxQL play critical roles in sorting fused proteins in the endosperm cells.

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“…Trans-acting interactions between prolamins and ER-residing chaperones, such as BiP, also play a role in prolamin retention by facilitating its folding and assembly (5,14,15). In rice, the localized targeting of prolamin mRNAs to distinct ER subdomains also facilitates the assembly and retention of these proteins (16,17). An essential role of protein-disulfide isomerase in the segregation of rice storage proteins within the ER lumen has also been proposed as a trans-factor (18).…”

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confidence: 99%

Relevant Elements of a Maize γ-Zein Domain Involved in Protein Body Biogenesis

Llop‐Tous

Madurga

Giralt

et al. 2010

Journal of Biological Chemistry

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The N-terminal proline-rich domain of ␥-zein (Zera) plays an important role in protein body (PB) formation not only in the original host (maize seeds) but in a broad spectrum of eukaryotic cells. However, the elements within the Zera sequence that are involved in the biogenesis of PBs have not been clearly identified. Here, we focused on amino acid sequence motifs that could be involved in Zera oligomerization, leading to PB-like structures in Nicotiana benthamiana leaves. By using fusions of Zera with fluorescent proteins, we found that the lack of the repeat region (PPPVHL) 8 of Zera resulted in the secretion of the fusion protein but that this repeat by itself did not form PBs. Although the repeat region containing eight units was the most efficient for Zera self-assembly, shorter repeats of 4 -6 units still formed small multimers. Based on site-directed mutagenesis of Zera cysteine residues and analysis of multimer formation, we conclude that the two N-terminal Cys residues of Zera (Cys 7 and Cys 9 ) are critical for oligomerization. Immunoelectron microscopy and confocal studies on PB development over time revealed that early, small, Zera-derived oligomers were sequestered in buds along the rough ER and that the mature size of the PBs could be attained by both cross-linking of preformed multimers and the incorporation of new chains of Zera fusions synthesized by active membrane-bound ribosomes. Based on these results and on the behavior of the Zera structure determined by molecular dynamics simulation studies, we propose a model of Zera-induced PB biogenesis.The mechanisms by which prolamins, which lack the ER 3 retention (H/K)DEL motif, are retained and assembled in the ER-derived PBs are only partially understood. Different factors act as determinants of PB biogenesis, some of them derived from cis-cargo properties and others with a cellular trans-origin (1). It has been proposed that the physico-chemical properties of prolamins, such as hydrophobicity and disulfide bond formation, promote specific interactions resulting in the formation of large self-assemblies that are responsible for their retention in the ER and PB formation (2-4). These polymers could be excluded because of their size from being carried by the COP II vesicles that transport cargo proteins to the Golgi complex (5). However, the generic COPII vesicles are flexible enough for large cargo loading, including that of procollagen (more than 300 nm in size) (6) and the collagen VII trimer (900 kDa) (7).In maize, four distinct types of prolamins (␣-, ␤-, ␥-, and ␦-zein) coexist in the PBs (8) and play distinct roles in PB formation. Recently, maize storage protein mutants created through RNAi showed that ␥-RNAi maize mutant lines exhibited slightly altered protein body formation and that a more drastic effect was observed in the ␤-␥ combined mutant, where protein bodies showed an irregular shape, particularly in their periphery (9).Various studies on zein accumulation in heterologous expression systems suggest that ␥-zein and ␤-zein mediate t...

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Targeting of Proteins to Endoplasmic Reticulum-Derived Compartments in Plants. The Importance of RNA Localization

Cited by 62 publications

References 34 publications

Cell Type–Specific Chromatin Decondensation of a Metabolic Gene Cluster in Oats

Cell Type–Specific Chromatin Decondensation of a Metabolic Gene Cluster in Oats

The Critical Role of Disulfide Bond Formation in Protein Sorting in the Endosperm of Rice

Relevant Elements of a Maize γ-Zein Domain Involved in Protein Body Biogenesis

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