Polyribosome formation in early wheat embryo germination independent of either transcription or polyadenylation

Spiegel, S.; Marcus, Abraham

doi:10.1038/256228a0

Cited by 119 publications

(52 citation statements)

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“…It has been shown that GSSG inhibits the initiation of protein synthesis in cell-free extracts from rabbit reticulocytes (4,10). Wheat embryos lack polysomes in the dry, quiescent state but polysomes appear shortly after initiation of germination (15) as has also been found for-N. crassa conidia (17). Endogenous ribosome activity is largely lost if embryos are desiccated after the early stages of imbibition but is regained upon reimbibition (3).…”

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confidence: 88%

“…Endogenous ribosome activity is largely lost if embryos are desiccated after the early stages of imbibition but is regained upon reimbibition (3). It has been established that protein synthesis which; occurs during the early stages of germination uses preexisting mRNA but the mechanism regulating the translation of the message has not been established (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Indirect evidence presented by Weeks and Marcus (18) implicates a sulfhydryl protein present in a partially purified message fraction as potentially important to template activity.…”

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confidence: 99%

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Role of Hydration State and Thiol-Disulfide Status in the Control of Thermal Stability and Protein Synthesis in Wheat Embryo

Fahey¹,

Stefano²,

Meier³

et al. 1980

Plant Physiol.

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Reduced (GSH), oxidized (GSSG), and protein-bound (PSSG) glutsthione were-determined in dry and hydrated wheat embryos. Dry embryos contained-about 0.6 tkmoles per gramdry weight each of GSSG and PSSG, and thege levels declned 5-to lO4fold within minutes after the onset of imbibition. GSH declined from about 8 to 2pmoles per gram over a peiod of 90 minutes. Similar changes occurred when embryos were hydrated by storage at 100% relative humidity. The decline in glutathione levels was not reversed-upon redrying hydrated enbryos. About 40% of the cysteine residues of embryo protein was found to be in the disulfide form in both dry and inbibd embryos. he -ability of wheat embryos to withstandheat shock was shown to correlate with water content but not GSSG content.Incorporation of 135SImethlonine-into protein was studied using a systen based upon wheat embryo extract (S23). Incorportion rate was found to be snsitive-to the-nature of thiol added to the system and to be decreased. by GSSG. S23 exhibited a substantial capacity to reduce GSSG and preparation of S23 having a GSSG content comparable to dry embryos requlredladltlon of large amounts of GSSG to-the extraction buffer .823 prepared in this fashion exhibited a marked decrease in ability to suppo protein syn-thesis. These results suggest that the early decrease in GSSG. during germination is necessary for optimal protein synthesis in wheat embryo. This is one ofa series ofstudies undertaken to identify biological systems in which changes in the glutathione thiol-disulfide status (9) might be of potential importance in regulating biological activity. -In an earlier study (6) we demonstrated that GSSG3 levels are higher in the asexual spores (conidia) than in the vegetative cells of the fungus Neurospora crassa and that this difference disappears during the first minutes of conidial germination. P.arallel changes occur in the level of PSSG, suggesting that reversible conversion of protein thiol groups to disulfide forms might be involved as part of a control process. The initial objective of the present studies was to ascertain whether similar changes in glutat" thione thiol-disulfide status occur during germination of seed embryos. The results obtained with wheat and-barley embryos, proved generally similar to those obtained with N. crassa conidia.What role do such thiol-disulfide changes play in seed embryos?Since disulfide proteins generally exhibit greater thermal stability than proteins lacking disulfide bonds (12) confer thermal stability upon proteins. The second objective in the present study was to differentiate the effects of dehydration and thiol-disulfide changes upon thermal stability in seed embryos.Another possibility is that thiol-disulfide reactions are involved in the control of protein synthesis. It has been shown that GSSG inhibits the initiation of protein synthesis in cell-free extracts from rabbit reticulocytes (4, 10). Wheat embryos lack polysomes in the dry, quiescent state but polysomes appear shortly after initiation of germinat...

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confidence: 88%

mentioning

confidence: 99%

Role of Hydration State and Thiol-Disulfide Status in the Control of Thermal Stability and Protein Synthesis in Wheat Embryo

Fahey¹,

Stefano²,

Meier³

et al. 1980

Plant Physiol.

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“…Although synthesis of messenger RNA has been shown to occur at the earliest times of wheat embryo imbibition [l], there is evidence to suggest that this mRNA synthesis is not required either for formation of polyribosomes or for the protein synthesis which occurs during the first 40 min of germination [2]. Accordingly, it has been inferred that this early protein synthesis is directed by mRNA which is transcribed prior to dehydration and then stored in the dry wheat embryo /2,3].…”

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confidence: 99%

Protein Synthesis in Imbibing Wheat Embryos

Cuming

Lane

1979

European Journal of Biochemistry

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Polypeptides synthesized by imbibing wheat embryos have been compared with those made by cell-free extracts programmed with bulk poly(A)-rich RNA from dry wheat embryos. Newly synthesized polypeptides, labeled with [35S]methionine, were resolved by one-dimensional and two-dimensional electrophoresis and then records of the separations were prepared by fluorography. When programmed by bulk poly(A)-rich RNA from dry wheat embryos, a nuclease-treated rabbit reticulocyte lysate synthesizes an array of polypeptides which is broadly similar to that formed when a wheat germ extract is programmed with the same RNA. Polypeptides made in both homologous and heterologous cell-free systems, under the direction of bulk poly(A)-rich RNA from dry wheat embryos, are broadly similar to those formed during early (0-40 min) imbibition of dry wheat embryos. As imbibition progresses beyond 40 min, there are profound changes in the one-dimensional and twodimensional electrophoretic distributions of newly made polypeptides present in the 23 000 x g supernatant fraction of cell-free homogenates; characteristically, low-molecular-weight and basic polypeptides comprise a diminishing proportion of the total polypeptides as imbibition progresses beyond 40 min. Ribosomal proteins are conspicuous among the proteins formed during early imbibition and especially prominent among the products formed when homologous cell-free polypcptide synthesis is programmed by bulk poly(A)-rich RNA from dry wheat embryos.

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“…The formation of polyribosomes at this developmental stage does not depend on transcription [6]. It is now evident that these phenomena represent a consequence of mobilization of the previously formed and stored mRNA.…”

Section: Introductionmentioning

confidence: 89%

Free poly(A) tracts complexed with protein in the cytoplasm of dried wheat embryos

Filimonov

Ajtkhozhin²

1977

FEBS Letters

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Polyribosome formation in early wheat embryo germination independent of either transcription or polyadenylation

Cited by 119 publications

References 16 publications

Role of Hydration State and Thiol-Disulfide Status in the Control of Thermal Stability and Protein Synthesis in Wheat Embryo

Role of Hydration State and Thiol-Disulfide Status in the Control of Thermal Stability and Protein Synthesis in Wheat Embryo

Protein Synthesis in Imbibing Wheat Embryos

Free poly(A) tracts complexed with protein in the cytoplasm of dried wheat embryos

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