The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Richard B Flavell - One of the best experts on this subject based on the ideXlab platform.
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Developmentally and transgene regulated nuclear processing of primary transcripts of Chalcone Synthase A in petunia
The Plant journal : for cell and molecular biology, 2000Co-Authors: M Metzlaff, Michael O'dell, Roger P. Hellens, Richard B FlavellAbstract:The introduction of Chalcone Synthase A transgenes into petunia plants can result in degradation of Chalcone Synthase A RNAs and loss of Chalcone Synthase, a process called cosuppression or post-transcriptional gene silencing. Here we show that the RNA degradation is associated with changes in premRNA processing, i.e. loss of tissue specificity in transcript cleavage patterns, accumulation of unspliced molecules, and use of template-specific secondary poly(A) sites. These changes can also be observed at a lower level in leaves but not flowers of nontransgenic petunias. Based on this, a model is presented of how transgenes may disturb the carefully evolved, developmentally controlled post-transcriptional regulation of Chalcone Synthase gene expression by influencing the survival rate of the endogenous and their own mRNA.
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Post-transcriptional gene silencing of Chalcone Synthase in transgenic petunias, cytosine methylation and epigenetic variation
The Plant Journal, 1999Co-Authors: Michael O'dell, M Metzlaff, Richard B FlavellAbstract:Summary Post-transcriptional degradation of Chalcone Synthase RNA transcripts often occurs in petunia plants with additional copies of Chalcone Synthase genes. The cytosine methylation status of selected restriction endonuclease sites was studied in the Chalcone Synthase endogenous genes and transgenes of these plants. Methylation patterns varied between transformants and within a series of epigenetically related plants. There was heterogeneity in promoter transgene methylation patterns within and/or between cells, between leaves and flowers and between tandemly duplicated sequences. Thus methylation patterns are determined by more than the local DNA sequence or site of insertion. A site in the 5′ enhancer of the 35S promoter was methylated more frequently in white flowers than in purple flowers. An EcoRII site within the coding sequence of the endogenous ChsA genes is developmentally regulated, being frequently methylated in leaves but rarely in petals of wild-type petunias or stable purple flowered transgenic plants. However, in petals of many transgenic plants, especially those that show extensive post transcriptional RNA degradation, the site is frequently methylated. Thus the transgenes influence developmental methylation of the endogenous genes. In the transgenes the EcoRII site is usually more frequently methylated in petals than in leaves. RNA degradation in petals is correlated in one set of epigenetically related transgenic plants with hypomethylation at the transgene EcoRII site in leaves. Possible relationships between the cytosine methylation patterns in vegetative and floral cells, epigenetic states of ChsA genes and the control of RNA transcript degradation are discussed.
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rna mediated rna degradation and Chalcone Synthase a silencing in petunia
Cell, 1997Co-Authors: M Metzlaff, Michael Odell, P D Cluster, Richard B FlavellAbstract:Abstract Transgenic Petunia plants with a chsA coding sequence under the control of a 35S promoter sometimes lose endogene and transgene Chalcone Synthase activity and purple flower pigment through posttranscriptional chsA RNA degradation. In these plants, shorter poly(A) + and poly(A) − chsA RNAs are found, and a 3′ end–specific RNA fragment from the endogene is more resistant to degradation. The termini of this RNA fragment are located in a region of complementarity between the chsA 3′ coding region and its 3′ untranslated region. Equivalent chsA RNA fragments remain in the white flower tissue of a nontransgenic Petunia variety. We present a model involving cycles of RNA–RNA pairing between complementary sequences followed by endonucleolytic RNA cleavages to describe how RNA degradation is likely to be promoted.
B. Karwatzki - One of the best experts on this subject based on the ideXlab platform.
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In situ localization of Chalcone Synthase in tannin-containing plants
Phytochemistry, 1993Co-Authors: B. Karwatzki, A. Herget, Ludger Beerhues, Rolf WiermannAbstract:Abstract Chalcone Synthase in leaves of Kalanchoe daigremontiana and Acorus calamus , and in phyllodes of Kalanchoe tubiflora was detected both enzymatically and immunochemically. In situ localization by indirect immunofluorescence revealed that, in all three systems, Chalcone Synthase is highly expressed in tannin-containing idioblasts. In A. calamus the enzyme is additionally present in oil cells. The spatial distribution of Chalcone Synthase did not change during organ development.
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Immunofluorescence localization of Chalcone Synthase in roots ofPisum sativum L. andPhaseolus vulgaris L. and comparable immunochemical analysis of Chalcone Synthase from pea leaves
Protoplasma, 1992Co-Authors: M. Rommeswinkel, B. Karwatzki, L. Beerhues, R. WiermannAbstract:Chalcone Synthase in roots of Pisum sativum and Phaseolus vulgaris was demonstrated enzymatically and immunochemically. In situ localization by indirect immunofluorescence revealed that Chalcone Synthase is chiefly present in the lateral regions of the calyptra, in the rhizodermis, and the cortex. In the central cylinder the enzyme protein is no longer detectable a short distance behind the meristem. Chalcone Synthase was not found in root tips of Zea mays . Two isoforms of Chalcone Synthase were separated by chromatofocusing of protein extracts from pea leaves. The two forms differed in their subunit molecular masses. The smaller isoform was not detected in roots.
M Metzlaff - One of the best experts on this subject based on the ideXlab platform.
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Novartis Foundation Symposium 214 ‐ Epigenetics - Transgene-promoted epigenetic switches of Chalcone Synthase activity in petunia plants.
Novartis Foundation symposium, 2007Co-Authors: R. B. Flavell, Michael O'dell, M MetzlaffAbstract:Epigenetic variation affecting pigment pattern formation in petunia flowers due to the insertion of transgenes encoding Chalcone Synthase is described. The loss of pigment formation in petals or parts of petals is due to the post-transcriptional degradation of Chalcone Synthase RNA, from both the endogenous petunia Chalcone Synthase genes and from the Chalcone Synthase transgenes. The RNA cleavage pathway and its control are described. Different epigenetic states of RNA breakdown are correlated with specific cytosine methylation changes in the coding sequences of the genes. The probability, extent and developmental location of Chalcone Synthase RNA breakdown are related to the number and organization of transgenes in the genome but epigenetic switches that affect RNA turnover probably occur in meristems and between sexual generations. Hypotheses to explain how the transgenes influence the levels of Chalcone Synthase RNA breakdown and how different epigenetic states are created are discussed.
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Developmentally and transgene regulated nuclear processing of primary transcripts of Chalcone Synthase A in petunia
The Plant journal : for cell and molecular biology, 2000Co-Authors: M Metzlaff, Michael O'dell, Roger P. Hellens, Richard B FlavellAbstract:The introduction of Chalcone Synthase A transgenes into petunia plants can result in degradation of Chalcone Synthase A RNAs and loss of Chalcone Synthase, a process called cosuppression or post-transcriptional gene silencing. Here we show that the RNA degradation is associated with changes in premRNA processing, i.e. loss of tissue specificity in transcript cleavage patterns, accumulation of unspliced molecules, and use of template-specific secondary poly(A) sites. These changes can also be observed at a lower level in leaves but not flowers of nontransgenic petunias. Based on this, a model is presented of how transgenes may disturb the carefully evolved, developmentally controlled post-transcriptional regulation of Chalcone Synthase gene expression by influencing the survival rate of the endogenous and their own mRNA.
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Post-transcriptional gene silencing of Chalcone Synthase in transgenic petunias, cytosine methylation and epigenetic variation
The Plant Journal, 1999Co-Authors: Michael O'dell, M Metzlaff, Richard B FlavellAbstract:Summary Post-transcriptional degradation of Chalcone Synthase RNA transcripts often occurs in petunia plants with additional copies of Chalcone Synthase genes. The cytosine methylation status of selected restriction endonuclease sites was studied in the Chalcone Synthase endogenous genes and transgenes of these plants. Methylation patterns varied between transformants and within a series of epigenetically related plants. There was heterogeneity in promoter transgene methylation patterns within and/or between cells, between leaves and flowers and between tandemly duplicated sequences. Thus methylation patterns are determined by more than the local DNA sequence or site of insertion. A site in the 5′ enhancer of the 35S promoter was methylated more frequently in white flowers than in purple flowers. An EcoRII site within the coding sequence of the endogenous ChsA genes is developmentally regulated, being frequently methylated in leaves but rarely in petals of wild-type petunias or stable purple flowered transgenic plants. However, in petals of many transgenic plants, especially those that show extensive post transcriptional RNA degradation, the site is frequently methylated. Thus the transgenes influence developmental methylation of the endogenous genes. In the transgenes the EcoRII site is usually more frequently methylated in petals than in leaves. RNA degradation in petals is correlated in one set of epigenetically related transgenic plants with hypomethylation at the transgene EcoRII site in leaves. Possible relationships between the cytosine methylation patterns in vegetative and floral cells, epigenetic states of ChsA genes and the control of RNA transcript degradation are discussed.
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rna mediated rna degradation and Chalcone Synthase a silencing in petunia
Cell, 1997Co-Authors: M Metzlaff, Michael Odell, P D Cluster, Richard B FlavellAbstract:Abstract Transgenic Petunia plants with a chsA coding sequence under the control of a 35S promoter sometimes lose endogene and transgene Chalcone Synthase activity and purple flower pigment through posttranscriptional chsA RNA degradation. In these plants, shorter poly(A) + and poly(A) − chsA RNAs are found, and a 3′ end–specific RNA fragment from the endogene is more resistant to degradation. The termini of this RNA fragment are located in a region of complementarity between the chsA 3′ coding region and its 3′ untranslated region. Equivalent chsA RNA fragments remain in the white flower tissue of a nontransgenic Petunia variety. We present a model involving cycles of RNA–RNA pairing between complementary sequences followed by endonucleolytic RNA cleavages to describe how RNA degradation is likely to be promoted.
Michael T Clegg - One of the best experts on this subject based on the ideXlab platform.
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nucleotide polymorphism in the Chalcone Synthase a locus and evolution of the Chalcone Synthase multigene family of common morning glory ipomoea purpurea
Molecular Ecology, 1997Co-Authors: Gavin A. Huttley, Mary L. Durbin, D. E. Glover, Michael T CleggAbstract:Chalcone Synthase (CHS) is a small multigene family with at least four members (CHS-A, B, C and PS) in common morning glory Ipomoea purpurea ROTH. The Chalcone Synthase enzyme performs the initial condensation reaction that results in the 15-carbon three-ring structure that is the backbone of flavonoid biosynthesis. The biochemical pathway that commences with CHS is important in plant disease defence, pigment biosynthesis and UV protection. Accordingly, it is of substantial interest to characterize levels and patterns of molecular diversity for genes that encode this important enzyme. We report the sequence of 19 CHS-A alleles from Mexican and American populations of common morning glory. American populations of this annual self-compatible vine are believed to have been introduced from Mexico, where the species is native. Individual plants were sampled from populations of common morning glory throughout Mexico and the south-eastern USA. Four American alleles were sequenced and these, together with one allele from Mexico City, were identical in primary nucleotide sequence. These data suggest a restricted origin for the American population, probably as a consequence of selection for domestication by pre-Columbian peoples. Additionally the Mitontic (Chiapas, Mexico) population is significantly more homogeneous than expected by chance indicating that this population may also have experienced a recent population bottleneck. Estimates of nucleotide diversity from the Mexican CHS-A alleles were high. We present evidence that these estimates may, in part, result from low to moderate levels of interlocus recombination/gene conversion. We also present evidence that the ancient duplication of the CHS gene family, preceding the origin of the genus Ipomoea, was associated with heterogeneity in the rate of substitution between the resulting gene family members. The group of gene family members whose sequences possess a signature amino acid of the closely related Stilbene Synthase exhibit a significantly faster proportional rate of nonsynonymous substitution.
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Nucleotide polymorphism in the Chalcone Synthase‐A locus and evolution of the Chalcone Synthase multigene family of common morning glory Ipomoea purpurea
Molecular Ecology, 1997Co-Authors: Gavin A. Huttley, Mary L. Durbin, D. E. Glover, Michael T CleggAbstract:Chalcone Synthase (CHS) is a small multigene family with at least four members (CHS-A, B, C and PS) in common morning glory Ipomoea purpurea ROTH. The Chalcone Synthase enzyme performs the initial condensation reaction that results in the 15-carbon three-ring structure that is the backbone of flavonoid biosynthesis. The biochemical pathway that commences with CHS is important in plant disease defence, pigment biosynthesis and UV protection. Accordingly, it is of substantial interest to characterize levels and patterns of molecular diversity for genes that encode this important enzyme. We report the sequence of 19 CHS-A alleles from Mexican and American populations of common morning glory. American populations of this annual self-compatible vine are believed to have been introduced from Mexico, where the species is native. Individual plants were sampled from populations of common morning glory throughout Mexico and the south-eastern USA. Four American alleles were sequenced and these, together with one allele from Mexico City, were identical in primary nucleotide sequence. These data suggest a restricted origin for the American population, probably as a consequence of selection for domestication by pre-Columbian peoples. Additionally the Mitontic (Chiapas, Mexico) population is significantly more homogeneous than expected by chance indicating that this population may also have experienced a recent population bottleneck. Estimates of nucleotide diversity from the Mexican CHS-A alleles were high. We present evidence that these estimates may, in part, result from low to moderate levels of interlocus recombination/gene conversion. We also present evidence that the ancient duplication of the CHS gene family, preceding the origin of the genus Ipomoea, was associated with heterogeneity in the rate of substitution between the resulting gene family members. The group of gene family members whose sequences possess a signature amino acid of the closely related Stilbene Synthase exhibit a significantly faster proportional rate of nonsynonymous substitution.
Rolf Wiermann - One of the best experts on this subject based on the ideXlab platform.
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In situ localization of Chalcone Synthase in tannin-containing plants
Phytochemistry, 1993Co-Authors: B. Karwatzki, A. Herget, Ludger Beerhues, Rolf WiermannAbstract:Abstract Chalcone Synthase in leaves of Kalanchoe daigremontiana and Acorus calamus , and in phyllodes of Kalanchoe tubiflora was detected both enzymatically and immunochemically. In situ localization by indirect immunofluorescence revealed that, in all three systems, Chalcone Synthase is highly expressed in tannin-containing idioblasts. In A. calamus the enzyme is additionally present in oil cells. The spatial distribution of Chalcone Synthase did not change during organ development.