Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A Chlamydomonas reinhardtii chloroplast transformant, designated MU7, carrying a chimeric (rbcL promoter: beta-glucuronidase [GUS]: psaB 3' end) gene whose transcripts have been found previously to be unstable in light (half-life of 20 min in light as opposed to a half-life of 5 h in the dark), was used to study the role of electron transport and of the redox state in the degradation of chloroplast transcripts in the light. Blocking photosynthetic electron transport with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) prevented the light-dependent breakdown of the pool of GUS transcripts in MU7 cells. Diamide, an oxidizing agent, caused a measurable delay in the degradation of GUS transcripts in the light. The addition of dithiothreitol (DTT), a dithiol reductant, to MU7 cells in which GUS transcript levels were stabilized by DCMU induced degradation of GUS transcripts. Similarly, DTT induced a decrease in the levels of GUS transcripts when added to MU7 cells in the dark period of the light/dark cycle, a period in which GUS transcript levels normally increase. The levels of transcripts of endogenous chloroplast genes were affected by DCMU and DTT in the same direction as levels of GUS transcripts. The results suggest a regulatory role of the redox state in the degradation of chloroplast transcripts in C. reinhardtii.
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PMID:The redox state regulates RNA degradation in the chloroplast of Chlamydomonas reinhardtii. 1059 24

Chloroplast transformation has many potential advantages for the production of recombinant proteins in plants. However, it has been reported that heterologous protein accumulation in chloroplasts could be hindered by post-transcriptional mechanisms not yet characterized. Here, we describe the development and characterization of transplastomic tobacco plants transformed with four different transformation vectors for the expression of human epidermal growth factor (hEGF). We showed that, although the corresponding transcript was present in all of the analyzed plants, hEGF could only be detected when fused to the first 186 amino acids of bacterial beta-glucuronidase (GUS). In addition, we observed that the expression levels of recombinant protein increased when plants were placed in the dark or when leaves were incubated in the presence of electron transport inhibitors, such as methyl viologen (MV) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). These results suggest that the mechanism responsible for hEGF instability in chloroplasts is regulated by light.
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PMID:Accumulation of hEGF and hEGF-fusion proteins in chloroplast-transformed tobacco plants is higher in the dark than in the light. 1658 96

Persistent light quality gradients in dense plant populations induce imbalances in the distribution of excitation energy between the photosystems. Plants counteract such conditions by re-adjusting the stoichiometry of photosystems, which involves control of photosynthesis gene expression both in chloroplasts and in the nucleus. Decisive control parameters are redox signals from the photosynthetic electron transport chain, one prominent is the plastoquinone (PQ) pool. In a recent study, a plastocyanin (PC)-promoter::beta-glucuronidase reporter gene construct in tobacco demonstrated reversible redox regulation in response to varying light qualities. Here, northern and Western analyses demonstrate that this promoter regulation also accounts for the accumulation of the endogenous tobacco PetE gene transcripts and the protein amounts of the encoded PC. Hence, the reporter gene construct reflects the natural regulation of this nuclear gene in tobacco. In kinetic experiments, the response of the construct to either oxidation or reduction of the PQ pool was tested by defined light quality shifts. The construct displayed upregulation in response to a reduction signal and downregulation in response to an oxidation signal, both with a half-time of about 24 h. The response was finished after 48 h. DCMU application abolished the upregulation in response to the reduction signal, indicating the dependence on thylakoid membrane electron transport. To study the redox-responsive promoter region in more detail, several promoter deletion constructs were tested for their responsiveness. All constructs displayed a reversible response to light-induced oxidation and reduction signals; however, a minimal promoter region localised between -168 to -79 bp upstream of the transcription start site was sufficient to confer this redox regulation. This indicates that photosynthetic redox signals act on distinct regions in the PC promoter in a manner independent from photoreceptors and upstream cis elements conferring high basic expression in the light.
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PMID:Photosynthetic redox regulation of the plastocyanin promoter in tobacco. 1841 38