Brittle-1, an Adenylate Translocator, Facilitates Transfer of Extraplastidial Synthesized ADP-Glucose into Amyloplasts of Maize Endosperms1

Shannon, Jack C.; Pien, Fang-Mei; Cao, Heping; Liu, Kang-Chien

doi:10.1104/pp.117.4.1235

Cited by 190 publications

(137 citation statements)

References 61 publications

Supporting

Mentioning

120

Contrasting

Order By: Relevance

“…It has been speculated that the cytosolic AGPase may facilitate the partitioning of carbon from sucrose into starch when there is a sufficient supply of sucrose in the endosperm (38), which would require the import of cytosolic ADP-glucose into the plastids. This import has been proposed to be accomplished through the action of the brittle-1 protein, an adenylate translocator with a common ADP-glucose-binding domain (48), for which we detected a seed-specific expression, thus supporting the evidence of cytosolic AGPase pools in seed tissues.…”

Section: Resultssupporting

confidence: 85%

Proteomic survey of metabolic pathways in rice

Koller

Washburn

Lange

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

373

224

View full text Add to dashboard Cite

A systematic proteomic analysis of rice (Oryza sativa) leaf, root, and seed tissue using two independent technologies, two-dimensional gel electrophoresis followed by tandem mass spectrometry and multidimensional protein identification technology, allowed the detection and identification of 2,528 unique proteins, which represents the most comprehensive proteome exploration to date. A comparative display of the expression patterns indicated that enzymes involved in central metabolic pathways are present in all tissues, whereas metabolic specialization is reflected in the occurrence of a tissue-specific enzyme complement. For example, tissuespecific and subcellular compartment-specific isoforms of ADPglucose pyrophosphorylase were detected, thus providing proteomic confirmation of the presence of distinct regulatory mechanisms involved in the biosynthesis and breakdown of separate starch pools in different tissues. In addition, several previously characterized allergenic proteins were identified in the seed sample, indicating the potential of proteomic approaches to survey food samples with regard to the occurrence of allergens.

show abstract

Section: Resultssupporting

confidence: 85%

Proteomic survey of metabolic pathways in rice

Koller

Washburn

Lange

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

373

224

View full text Add to dashboard Cite

show abstract

“…To estimate cross-contamination between the two tissues, we extracted RNA and amplified transcripts of Brittle1 (Bt1) and Viviparous1 (Vp1), which are genes preferentially expressed in the starchy endosperm and aleurone cells, respectively (Shannon et al, 1998;Cao et al, 2007;Kirchberger et al, 2007). Quantification via real-time RT-PCR showed a 12.8-fold enrichment of Bt1 transcripts in starchy endosperm samples and 29.7-fold enrichment of Vp1 transcripts in aleurone samples, indicating very low cross-contamination between the two cell types ( Figures 1A and 1B).…”

Section: Zeins Are Expressed In Both Aleurone and Starchy Endosperm Cmentioning

confidence: 99%

Delivery of Prolamins to the Protein Storage Vacuole in Maize Aleurone Cells

et al. 2011

View full text Add to dashboard Cite

Zeins, the prolamin storage proteins found in maize (Zea mays), accumulate in accretions called protein bodies inside the endoplasmic reticulum (ER) of starchy endosperm cells. We found that genes encoding zeins, a-globulin, and legumin-1 are transcribed not only in the starchy endosperm but also in aleurone cells. Unlike the starchy endosperm, aleurone cells accumulate these storage proteins inside protein storage vacuoles (PSVs) instead of the ER. Aleurone PSVs contain zeinrich protein inclusions, a matrix, and a large system of intravacuolar membranes. After being assembled in the ER, zeins are delivered to the aleurone PSVs in atypical prevacuolar compartments that seem to arise at least partially by autophagy and consist of multilayered membranes and engulfed cytoplasmic material. The zein-containing prevacuolar compartments are neither surrounded by a double membrane nor decorated by AUTOPHAGY RELATED8 protein, suggesting that they are not typical autophagosomes. The PSV matrix contains glycoproteins that are trafficked through a Golgi-multivesicular body (MVB) pathway. MVBs likely fuse with the multilayered, autophagic compartments before merging with the PSV. The presence of similar PSVs also containing prolamins and large systems of intravacuolar membranes in wheat (Triticum aestivum) and barley (Hordeum vulgare) starchy endosperm suggests that this trafficking mechanism may be common among cereals.The cereal endosperm consists of three main cell types: an inner mass of starchy endosperm cells, one to three layers of epidermal aleurone cells, and the transfer cells that contact the maternal vascular tissue (Olsen, 2004). The starchy endosperm accounts for 80 to 90% of the grain weight and contains large amounts of storage proteins and starch. These cells undergo programmed cell death during maturation. Aleurone cells are rich in protein storage vacuoles (PSVs), minerals, and lipid bodies and remain alive during seed development. It is assumed that the breakdown of proteins localized to PSVs in aleurone cells provides an essential source of the amino acids necessary for the synthesis of hydrolytic enzymes required for mobilizing food stored in the starchy endosperm (Filner and Varner, 1967;Jacobsen et al., 1988;Bethke et al., 1998).Besides its biological relevance as a model to study plant development, cell differentiation, and programmed cell death, the cereal endosperm is very important in terms of its nutritional value. Cereal grains contain less protein than do legume seeds, but because cereals are produced and consumed in much larger quantities, they are the main source of protein for the nutrition of humans and livestock (Shewry and Halford, 2002). The major storage proteins in maize (Zea mays) kernels are the alcoholsoluble prolamins, a type of storage proteins present only in grasses. Maize prolamins, referred to as zeins, are divided into different types: a-, b-, g-, and d-zeins (Coleman and Larkins, 1999) that differ in amino acid composition and structural properties (Shewry and Halford, 2002)...

show abstract

“…Another potential target relevant to starch metabolism, Brittle-1, was shown to be an ADP-glucose transporter after its identification in mutant maize enriched in sugar and deficient in starch (31). The contribution of Brittle-1 gained prominence in subsequent studies showing that the cytosol, rather than the plastid, is the major site of ADP-glucose formation in wheat starchy endosperm (17,32).…”

Section: Identification Of Members Of the Ferredoxin͞trx System And Smentioning

confidence: 99%

A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts

Balmer

Vensel

Cai

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

161

137

View full text Add to dashboard Cite

A growing number of processes throughout biology are regulated by redox via thiol-disulfide exchange. This mechanism is particularly widespread in plants, where almost 200 proteins have been linked to thioredoxin (Trx), a widely distributed small regulatory disulfide protein. The current study extends regulation by Trx to amyloplasts, organelles prevalent in heterotrophic plant tissues that, among other biosynthetic activities, catalyze the synthesis and storage of copious amounts of starch. Using proteomics and immunological methods, we identified the components of the ferredoxin͞Trx system (ferredoxin, ferredoxin-Trx reductase, and Trx), originally described for chloroplasts, in amyloplasts isolated from wheat starchy endosperm. Ferredoxin is reduced not by light, as in chloroplasts, but by metabolically generated NADPH via ferredoxin-NADP reductase. However, once reduced, ferredoxin appears to act as established for chloroplasts, i.e., via ferredoxinTrx reductase and a Trx (m-type). A proteomics approach in combination with affinity chromatography and a fluorescent thiol probe led to the identification of 42 potential Trx target proteins, 13 not previously recognized, including a major membrane transporter (Brittle-1 or ADP-glucose transporter). The proteins function in a range of processes in addition to starch metabolism: biosynthesis of lipids, amino acids, and nucleotides; protein folding; and several miscellaneous reactions. The results suggest a mechanism whereby light is initially recognized as a thiol signal in chloroplasts, then as a sugar during transit to the sink, where it is converted again to a thiol signal. In this way, amyloplast reactions in the grain can be coordinated with photosynthesis taking place in leaves.redox regulation ͉ target proteins ͉ ferredoxin-thioredoxin reductase O ur understanding of the function of the regulatory disulfide protein thioredoxin (Trx) has increased dramatically in the past few years, with the advent of new methodologies. Recent approaches make it possible to identify proteins linked to Trx by combining proteomics with affinity chromatography (1) or thiol probes (2-4). These capabilities have defined an extended role of Trx in chloroplasts (1, 5) and helped elucidate its function in other plant systems: mitochondria (6), seeds (2,3,7,8), and seedlings (4, 9). Currently almost 200 proteins appear to be linked to Trx in plants (10). One major organelle that has been neglected, however, is the amyloplast, a plastid of heterotrophic tissues that performs a wide range of biosynthetic reactions, including the synthesis and storage of abundant quantities of starch.To help fill this gap, we have applied proteomic and immunological approaches to investigate the occurrence and function of Trx in amyloplasts. We now report evidence that amyloplasts isolated from wheat starchy endosperm resemble chloroplasts in containing a complete ferredoxin͞Trx system composed of ferredoxin, ferredoxin-Trx reductase (FTR), and Trx (m-type). Application of affinity chromatography and fl...

show abstract

Brittle-1, an Adenylate Translocator, Facilitates Transfer of Extraplastidial Synthesized ADP-Glucose into Amyloplasts of Maize Endosperms1

Cited by 190 publications

References 61 publications

Proteomic survey of metabolic pathways in rice

Proteomic survey of metabolic pathways in rice

Delivery of Prolamins to the Protein Storage Vacuole in Maize Aleurone Cells

A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts

Contact Info

Product

Resources

About