Developmental Regulation of the Plastid Protein Import Apparatus

Dahlin, Clas; Cline, Kenneth

doi:10.2307/3869301

Cited by 42 publications

(30 citation statements)

References 9 publications

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“…In almost all cases studied, the precursor proteins appeared to be continuously imported into the organelles (8)(9)(10). Although various plastid types may exhibit different transport competences for certain nuclearencoded plastid precursor proteins, as discussed previously (11)(12)(13), none of these polypeptides could be detected in vivo. In the present paper, however, the nuclear-encoded key enzyme of chlorophyll biosynthesis in higher plants, the lightdependent NADPH:protochlorophyllide (Pchlide) oxidoreductase (POR; EC 1.3.1.33) (14,15), has been shown to accumulate in its precursor form, pPORA, in vivo. pPORA's translocation across the plastid envelope is regulated through its substrate, Pchlide (16,17).…”

mentioning

confidence: 94%

A plastid enzyme arrested in the step of precursor translocation in vivo.

Reinbothe¹,

Reinbothe²,

Neumann³

et al. 1996

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

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mentioning

confidence: 94%

A plastid enzyme arrested in the step of precursor translocation in vivo.

Reinbothe¹,

Reinbothe²,

Neumann³

et al. 1996

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

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“…The third identified component, Ptc52, displays similarity to three, at first glance, quite unrelated proteins: the lethal leaf spot protein Lls1 (37), Tic55 (38), and the recently identified chlorophyllide a oxygenase (Cao) (19) (Fig. 3).…”

Section: The Ptc Complex Contains Pchlide and A Putative Pchlide A Oxmentioning

confidence: 99%

“…Jarvis et al (18) demonstrated that ''twin components'' of the same regulatory GTP-binding protein, Toc34 and Toc33, are differentially expressed during plant development. In 1991, Dahlin and Cline (19) observed that protein import is determined by developmental fate and age of the plant, implying a rather flexible nature of the responsible import machinery.…”

mentioning

confidence: 99%

Identification of plastid envelope proteins required for import of protochlorophyllide oxidoreductase A into the chloroplast of barley

Reinbothe

Quigley

Gray

et al. 2004

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

100

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Chloroplasts synthesize an abundance of different tetrapyrrole compounds. Among them are chlorophyll and its precursor protochlorophyllide (Pchlide), which accumulate in light-and dark-grown plants, respectively. Pchlide is converted to chlorophyllide by virtue of the NADPH:Pchlide oxidoreductase (POR), which, in angiosperms, is the only known light-dependent enzyme of the chlorophyll biosynthetic pathway. In etiolated barley plants, two closely related POR proteins exist termed PORA and PORB, which are nuclear gene products. Here we identified plastid envelope proteins that interact with the cytosolic PORA precursor (pPORA) during its posttranslational chloroplast import. We demonstrate that pPORA interacts with several previously unreported components. Among them is a Pchlide a oxygenase, which provides Pchlide b as import substrate for pPORA, and a tyrosine aminotransferase thought to be involved in the synthesis of photoprotective vitamin E. Two other constituents were found to be orthologs of the GTP-binding proteins Toc33͞34 and of the outer plastid envelope protein Oep16.

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“…Indications of such mechanisms in action were observed, e.g. during the preferential in vitro import of proteins into chloroplasts versus leucoplasts (19), for "younger" versus "older" plastids (20), or plastids of nitrogen-fixing versus nonfixing nodules (21). Toc75-encoding mRNA levels, the outer envelope channel protein, also change in a tissue-specific manner (leaf versus roots) (16).…”

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confidence: 99%

Evidence That the Plastid Translocon Tic40 Components Possess Modulating Capabilities

Taylor

Argenton

et al. 2005

Journal of Biological Chemistry

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The transport of proteins into the plastid is a process that faces changing cellular needs such as the situation found in different plant organs or developing tissues. The plastid translocon must therefore be responsive to the changing cell environment to deliver efficiently different arrays of structurally diverse proteins. Although the Tic40-related envelope proteins appear to be translocon components designed to address the varying needs of protein translocation, details of their involvement remain elusive. This study was thus designed to combine plant-based experiments and yeast mitochondrion-based approaches for unveiling clues related to how the Tic40 components may behave during the protein translocation process. The main findings related to how Tic40 proteins may work are: 1) natural fluctuations are apparent in developing tissues, in different organs of the same plant, and in different species; 2) transgenic Arabidopsis seedlings can tolerate functionally a wide range of variations in Tic40 levels, from partial suppression to excessive production; 3) the Tic40 proteins themselves exhibit configurational changes in their association with yeast mitochondria in response to different carbon sources; 4) the presence of Tic40 proteins in yeast mitochondria influences regulatory aspects of the mitochondrial translocon; and 5) the Tic40 proteins associate with mitochondrial translocon components involved in regulatory-like events. The combined data provide evidence that Tic40 proteins possess modulating capabilities.Plastids are diverse in structure and function and occupy key roles in a variety of biosynthetic activities that take place in the ever changing environment of a plant cell. The role of plastids requires frequent adjustments to accommodate varying cellular needs such as those occurring in different organs, during development, during adaptation to external stimuli, or even a combination of needs. The adjustments required can be relatively subtle or distinct. The ability of the plastid to address such needs is dependent on its compositional status, e.g. chloroplasts versus leucoplasts. Although it is well established that changes to plastidial structure and function are governed predominantly by mechanisms that control gene expression (nuclear and organellar), there is growing evidence that the protein transport process contributes additionally to certain facets of these regulatory mechanisms. The involvement of protein transport in the various mechanisms of plastidial change is not unfounded because most of the plastid proteins involved are made as larger precursors before incorporation into organelles. The protein transport machinery of the plastid envelope (the plastid translocon) must therefore be accommodative in its ability to handle in an efficient manner a diverse, ever changing array of proteins. The proteins being handled range from different proteins to structural variations of the same protein.The plastid translocon is also afforded a position where additional "modulating" mechanisms can b...

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Developmental Regulation of the Plastid Protein Import Apparatus

Cited by 42 publications

References 9 publications

A plastid enzyme arrested in the step of precursor translocation in vivo.

A plastid enzyme arrested in the step of precursor translocation in vivo.

Identification of plastid envelope proteins required for import of protochlorophyllide oxidoreductase A into the chloroplast of barley

Evidence That the Plastid Translocon Tic40 Components Possess Modulating Capabilities

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