Tic32, an essential component in chloroplast biogenesis.

Hörmann, Friederike; Küchler, Michael; Sveshnikov, Dmitry S.; Oppermann, U.; Li, Yong; Soll, Jürgen

doi:10.1074/jbc.a402817200

Cited by 21 publications

(24 citation statements)

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“…For example the schlepperless ( slp ) and tic32 mutants lack a chaperonin‐60a protein required for normal thylakoid development and a component of the plastid envelope protein translocation apparatus, respectively, but in both cases the embryo undergoes morphogenesis as far as heart stage before seed abortion occurs (Apuya et al. , 2001; Hörmann et al. , 2004).…”

Section: Discussionmentioning

confidence: 99%

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The plastidial glucose-6-phosphate/phosphate antiporter GPT1 is essential for morphogenesis in Arabidopsis embryos

et al. 2010

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SUMMARYThe glucose-6-phosphate/phosphate antiporter GPT1 is a major route of entry of carbon into nonphotosynthetic plastids. To discover its importance in oilseeds, we used a seed-specific promoter to generate lines of Arabidopsis thaliana with reduced levels of GPT1 in developing embryos. Strong reductions resulted in seed abortion at the end of the globular stage of embryo development, when proplastids in normal embryos differentiate and acquire chlorophyll. Seed abortion was partly dependent on the light level during silique development. Embryos in seeds destined for abortion failed to undergo normal morphogenesis and were 'raspberry-like' in appearance. They had ultrastructural and biochemical defects including proliferation of peroxisomes and starch granules, and altered expression of genes involved in starch turnover and the oxidative pentose phosphate pathway. We propose that GPT1 is necessary for early embryo development because it catalyses import into plastids of glucose-6-phosphate as the substrate for NADPH generation via the oxidative pentose phosphate pathway. We suggest that low NADPH levels during plastid differentiation and chlorophyll synthesis may result in generation of reactive oxygen species and triggering of embryo cell death.

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Section: Discussionmentioning

confidence: 99%

“…, 2004). For example, developmental arrest occurs in mutants that lack components of the plastid protein import machinery (Hörmann et al. , 2004; Hust and Gutensohn, 2006), and in numerous mutants defective in proteins putatively involved in chloroplast protein folding, protein synthesis and membrane synthesis and assembly (e.g.…”

Section: Introductionmentioning

confidence: 99%

The plastidial glucose-6-phosphate/phosphate antiporter GPT1 is essential for morphogenesis in Arabidopsis embryos

et al. 2010

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“…3), suggesting roles in the regulation of import in response to endogenous redox status (Bédard & Jarvis, 2005). Whereas Tic62 and Tic32 each possess NAD(P)H binding sites, the Tic55 protein has a Rieske iron‐sulphur centre and a mononuclear iron‐binding site (Caliebe et al ., 1997; Küchler et al ., 2002; Hörmann et al ., 2004; Stengel et al ., 2008). The binding of NAD(P)H to these components might convey redox information to the translocation machinery.…”

Section: Later Stages Of the Toc/tic Pathwaymentioning

confidence: 99%

Targeting of nucleus‐encoded proteins to chloroplasts in plants

2008

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ReviewB l a c k w e l l P u b l i s h i n g L t d O x f o r d , U K N P H N e w P h y t o l o g i s t 0 0 2 8 -6 4 6 X 1 4 6 9 -8 1 3 7 © T h e A u t h o r s ( 2 0 0 8 ) . J o u r n a l c o m p i l a t i o n © N e w P h y t o l o g i s t ( 2 0 0 8 ) 10.1111/j. 1469-8137.2008 SummaryMost chloroplast proteins are encoded in the nucleus and synthesized on free, cytosolic ribosomes in precursor form. Each precursor has an amino-terminal extension called a transit peptide, which directs the protein through a post-translational targeting pathway and is removed upon arrival inside the organelle. This 'protein import' process is mediated by the coordinate action of two multiprotein complexes, one in each of the envelope membranes: the TOC and TIC (Translocon at the Outer/ Inner envelope membrane of Chloroplasts) machines. Many components of these complexes have been identified biochemically in pea; these include transit peptide receptors, channel proteins, and molecular chaperones. Intriguingly, the Arabidopsis genome encodes multiple, homologous genes for receptor components of the TOC complex. Careful analysis indicated that the different receptor isoforms operate in different import pathways with distinct precursor recognition specificities. These 'substrate-specific' import pathways might play a role in the differentiation of different plastid types, and/or act to prevent deleterious competition effects between abundant and nonabundant precursors. Until recently, all proteins destined for internal chloroplast compartments were thought to possess a cleavable transit peptide, and to engage the TOC/TIC machinery. New studies using proteomics and other approaches have revealed that this is far from true. Remarkably, a significant number of chloroplast proteins are transported via a pathway that involves the endoplasmic Plastids are a diverse group of organelles found ubiquitously in plant cells (Whatley, 1978), as well as in apicomplexan parasites (Foth & McFadden, 2003). The most prominent and wellstudied members of this plastid family are the chloroplasts. These contain the green pigment chlorophyll and carry out the light-driven carbon fixation reactions of photosynthesis, as well as important steps in the biosynthesis of many essential primary and secondary metabolites (Nelson & Ben-Shem, 2004;Lopez-Juez & Pyke, 2005). Other plastid family members are the amyloplasts, which contain large amounts of starch and play important roles in energy storage and gravitropism, and the chromoplasts, which accumulate red, orange or yellow carotenoid pigments and act as attractants in flowers and fruits (Neuhaus & Emes, 2000;Lopez-Juez & Pyke, 2005). Like mitochondria, plastids entered the eukaryotic lineage through endosymbiosis. It is thought that they evolved monophyletically from an ancient photosynthetic prokaryote similar to extant cyanobacteria (Larkum et al., 2007; ReyesPrieto et al., 2007). While plastids retain a functional genetic system of their own, the organellar genome is greatly reduced and typically encodes just ...

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“…Some cyanobacterial proteins contain cofactor-binding motifs similar to those found in Tic62, Tic55 and Tic32. Tic55 contains a Rieske iron-sulphur centre and a mononuclear iron-binding site [11], and Tic62 and Tic32 each have a NAD(P)-binding motif [12,13]. No prokaryotic counterparts have been detected by direct sequence comparison for the other subunits that compose the translocons, which may indicate that they have evolved from the proteome of the ancestral host to fulfil specific functions demanded after the development of plastids and to ensure the specificity of the transport process in the outer/inner envelope membranes of chloroplasts.…”

Section: Introductionmentioning

confidence: 99%

Tic62: a protein family from metabolism to protein translocation

Balsera¹,

Stengel²,

Soll³

et al. 2007

BMC Evol Biol

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Background: The function and structure of protein translocons at the outer and inner envelope membrane of chloroplasts (Toc and Tic complexes, respectively) are a subject of intensive research. One of the proteins that have been ascribed to the Tic complex is Tic62. This protein was proposed as a redox sensor protein and may possibly act as a regulator during the translocation process. Tic62 is a bimodular protein that comprises an N-terminal module, responsible for binding to pyridine nucleotides, and a C-terminal module which serves as a docking site for ferredoxin-NAD(P)-oxido-reductase (FNR). This work focuses on evolutionary analysis of the Tic62-NAD(P)-related protein family, derived from the comparison of all available sequences, and discusses the structure of Tic62.

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Tic32, an essential component in chloroplast biogenesis.

Cited by 21 publications

References 0 publications

The plastidial glucose-6-phosphate/phosphate antiporter GPT1 is essential for morphogenesis in Arabidopsis embryos

The plastidial glucose-6-phosphate/phosphate antiporter GPT1 is essential for morphogenesis in Arabidopsis embryos

Targeting of nucleus‐encoded proteins to chloroplasts in plants

Tic62: a protein family from metabolism to protein translocation

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