Protein synthesis by poly somes isolated from wheat leaves

Musk, P.; Chakravorty, Arun K.; Scott, K. J.

doi:10.1093/oxfordjournals.pcp.a075935

Cited by 3 publications

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“…We have demonstrated previously that, during cell-free translation, each ribosome translates the mRNA to which it is attached only once (20,21). This observation rules out the second possibility that some polysomal mRNA molecules may be translated at a greater frequency.…”

Section: Discussionmentioning

confidence: 81%

“…This observation rules out the second possibility that some polysomal mRNA molecules may be translated at a greater frequency. It has also been established that the size classes of polypeptides radiolabeled in vitro reflect the size classes of mRNA molecules that specify them (20,21). The increased synthesis of some size classes of polypeptides by the polysomes from inoculated leaves (Fig.…”

Section: Discussionmentioning

confidence: 95%

“…Aurintricarboxylic acid, a potent inhibitor of polypeptide chain initiation (14,18), has no effect on cell-free polysomal mRNA translation. This observation suggests that, once a ribosome has completed the translation of a polysomal mRNA, it does not reinitiate a new polypeptide chain (20,21). Consequently, the size classes of polypeptides radiolabeled in vitro correspond to the size classes of mRNA molecules present in the polysome preparation.…”

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confidence: 95%

“…We have developed a method for characterizing polysomal mRNA populations by in vitro translation of wheat leaf polysomes in a cell-free system followed by analytical gel electrophoresis of the radiolabeled polypeptides (20,21). The isolated polysomes consist of mRNA-bound ribosomes, each of which contains an in vivoinitiated polypeptide chain.…”

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confidence: 99%

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Changes in Wheat Leaf Polysomal Messenger RNA Populations during the Early Stages of Rust Infection

Pure¹,

Chakravorty²,

Scott³

1980

Plant Physiol.

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Polysomes isolated from a susceptible variety of wheat leaves (cultivar W2691) and those inoculated with the wheat stem rust fungus (f. sp. tritici, race 126-ANZ-6, 7) were incubated in a cell-free protein-synthesizing system. Under these conditions, different size classes of polypeptides, ranging in molecular weight from 10,000 to 80,000, are radiolabeled. Using double-isotope labeling technique, we show that some discrete size classes of polypeptides are synthesized in significantly greater quantitites by polysomes from inoculated leaves compared to the corresponding size classes synthesized by polysomes from healthy leaves. These results confirm our previous observation that there are signifkant changes in the wheat leaf polysomal messenger RNA populations at 3 days after inoculation with the rust fungus.The effects of the organeLe-specific inhibitors of protein synthesis, chloramphenicol and lincomycin, on in vitro polysomal messenger RNA translation were investigated. The polypeptides synthesized by polysomes from healthy and inoculated leaves in the presence of chloramphenicol were compared. The results show that, even in the presence of this antibiotic, the polysomes from Inoculated leaves synthesize greater quantities of some size classes of polypeptides. These data indicate that changes in polysomal messenger RNA populations involve, at least in part, cytoplasniic messenger RNA.Recent investigations in this and other laboratories indicated that there are marked changes in the pattern of gene expression in susceptible varieties of host plants during the initial stages of rust infection (see ref. 5 for a review). In a number of different rust infected host plants, it has been reported that there are increases in the synthesis and accumulation of ribosomal RNA (26,28) as well as messenger-like RNA (4,25,27). Infection of higher plants by obligate fungal pathogens is accompanied by major changes in the metabolism of the host plants (23). These metabolic transitions require the synthesis of new messenger RNA (mRNA) and enzymes. There are very few reports in the literature providing direct evidence for changes in mRNA populations in plants during the early stages of host-parasite interactions.

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Section: Discussionmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 95%

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confidence: 95%

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confidence: 99%

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