The increased production of ethylene during carnation petal senescence regulates the transcription of the GSTI gene encoding a subunit ofglutathione-S-transferase. We have investigated the molecular basis for this ethyleneresponsive transcription by examining the cis elements and trans-acting factors involved in the expression of the GSTI gene. Transient expression assays following delivery ofGSTI 5' flanking DNA fused to a P-glucuronidase reporter gene were used to functionally define sequences responsible for ethyleneresponsive expression. Deletion analysis of the 5' fanking sequences of GST1 identifted a single positive regulatory element of 197 bp between -667 and -470 necesary for ethylene-responsive expression. The sequences within this ethylene-responsive region were further localized to 126 bp between -596 and -470. The ethylene-responsive element (ERE) within this region conferred ethylene-regulated expression upon a mi l cauliflower mosaic virus-35S TATA-box promoter in an orientation-independent manner. Gel electrophoresis mobilityshift assays and DNase I footprinting were used to identify proteins that bind to sequences within the ERE. Nuclear proteins from carnation petals were shown to specifically interact with the 126-bp ERE and the presence and binding of these proteins were independent of ethylene or petal senescence. DNase I footprinting defined DNA sequences between -510 and -488 within the ERE specifically protected by bound protein. An 8-bp sequence (ATTTCAAA) within the protected region shares si ant homology with promoter sequences required for ethylene responsiveness from the tomato fruitripening E4 gene.
The proteases involved in proteolytic degradation in the thylakoid lumen are largely unknown. Western analysis with an antibody against the Escherichia coli periplasmic serine protease DegP suggested that pea chloroplasts contain a homologue of this protease. This homologue was peripherally bound to the luminal side of the thylakoid membrane and could only be removed by a combination of high salt and non-ionic detergent. Its level increased almost 2-fold in pea seedlings exposed to elevated temperature for 4 h, suggesting this protease's role in the chloroplast's heat response. Isolated thylakoid membranes containing the chloroplastic homologue of DegP degraded -casein, an in vitro substrate of the bacterial protease. This activity was partially inhibited by a serine protease inhibitor, suggesting that at least part of the casein-degrading activity in the thylakoid membrane is attributable to DegP. The existence of chloroplastic DegP was further supported by isolating a full-length Arabidopsis cDNA (designated AtDegP) encoding a protein that is 37% identical and 60% similar to the E. coli protease. The amino terminus of the deduced amino acid sequence contained a bipartite transit peptide, typical of proteins targeted to the thylakoid lumen, and the mature portion of the protein contained the highly conserved serine protease catalytic triad His-Asp-Ser. The possible physiological roles of chloroplastic DegP protease are discussed.The chloroplast, the photosynthetic organelle of eukaryotic cells, is composed of six compartments: three different membranes and the three aqueous compartments delimited by them. The chloroplast envelope, composed of an outer membrane, an inner membrane, and an intramembrane space, surrounds the stroma, the soluble compartment where most carbon metabolism reactions take place. The third membrane is the extensive network of thylakoid membranes, harboring the photosynthetic antennae, the photosynthetic electron transport system, and the ATP synthesis machinery. The sixth compartment is the thylakoid lumen, into which protons are pumped to form a proton gradient across the thylakoid membrane. This gradient is the driving force for ATP synthesis. Proteins found within the lumen, either soluble or bound to the inner side of the thylakoid membrane, include the oxygenevolving complex of photosystem II, components of the photosynthetic electron transport system, and many as yet unidentified proteins. As in other biological systems, maintenance of the lumen is expected to require protein degradation to remove damaged or otherwise nonfunctional proteins. However, the proteolytic machinery in this compartment has never been detailed.Many examples of protein degradation in the chloroplast have been documented (for review, see Ref. 1). Specific degradation of luminal proteins has also been demonstrated, with plastocyanin being the best characterized example. When Chlamydomonas cells are grown in a Cu 2ϩ -deficient medium, apoplastocyanin is synthesized, imported into the chloroplast, and transloca...
Chromoplasts are carotenoid-accumulating plastids found in the corollas and fruits of many higher plants. In most cases, the pigment in these plastids is accumulated with the aid of carotenoid-associated proteins located within unique structures. This paper reports the isolation and characterization of the cDNA (CHRC) from Cucumis sativus corollas which encodes the chromoplast-specific carotenoid-associated protein CHRC. The transit peptide cleavage site was determined and, using a chloroplast uptake system, it is shown that CHRC can be post-translationally targeted to these plastids where it is peripherally associated with thylakoids. Analysis of CHRC transcript level in Cucumis sativus revealed its temporal and tissue-specific regulation: the transcript was detected only in corollas, where its level increased in parallel to flower development, peaking just before anthesis. CHRC shares significant homology (59%) with the gene coding for fibrillin-a protein in Capsicum annuum red fruits whose function is essentially identical to that of CHRC. A CHRC fragment including the potential active site of the protein was used as a probe in Northern blot analyses of floral and fruit tissues from various plants containing chromoplasts of different types: CHRC homologs of similar sizes were revealed in all cases. The existence of a group of homologous genes coding for chromoplast-specific proteins which aid in the sequestration of carotenoids within specific structures is proposed.
The broad host range of arbuscular mycorrhizal (.4M) fungi differs from the specificity encountered in biotrophic pathogens. We summarize here the basic plant strategies of defence plant responses to colonization -with pathogenic micro-organisms and evaluate their possible involvement in AM performance. Detailed evidence ts presented that, during early colonization of plant roots by symbiotic Glomus, defence-related root responses are induced and then subsequently suppressed. In AM interactions, the broad host-range infection capacity and the induction of defence-related genes suggests that the compatible interaction is dominant. These results are discussed in relation to the possible conclusion that AM fungi might Jack avirulence homologues or alternatively, that the factor causing suppression of the host defence response might be dominant.
In this paper we present the structural analysis of two tightly linked genes from the glutathione S-transferase (GST) gene family in carnation (Dianthus caryophyllus). Southern blot analysis and restriction endonuclease mapping revealed a single cloned region of the carnation genome was highly homologous to the previously characterized ethylene-responsive GST mRNA expressed in flower petals during senescence. Nucleotide sequencing of this region revealed the presence of two tandemly arranged genes designated GST1 and GST2. Comparison of the nucleotide sequences of the cloned genomic region with the previously characterized GST cDNA clone pSR8 revealed that GST1 contains the entire transcription unit in 10 exons interrupted by 9 introns. The transcription unit of GST2 was found to be very similar to GST1 with complete conservation of intron position. In addition, the length and nucleotide sequences of the two genes' introns were highly conserved. GST2 was not completely represented by the cloned genomic region, missing the 3' portion of the transcription unit. Primer extension analysis indicated a single transcriptional start site for transcripts which accumulate in senescing carnation petals. The 5'-flanking sequences of GST1 and GST2 were compared and regions of homology and divergence identified. These upstream sequences were compared with other plant ethylene-responsive genes and GST genes and several sequence motifs of potential importance in the regulation of GST expression were identified. A chimeric gene constructed between -1457 bp of the 5'-flanking DNA of GST1 and the coding region of beta-glucuronidase was found to confer ethylene-inducible expression in flower petals following delivery of the construct into tissue by particle bombardment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.