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Jean-marc Brillouet - One of the best experts on this subject based on the ideXlab platform.
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On the Role of Chloroplasts in the Polymerization of Tannins in Tracheophyta: A Monograph
American Journal of Plant Sciences, 2015Co-Authors: Jean-marc BrillouetAbstract:Proanthocyanidins are formed in the chlorophyllous organs of Tracheophyta from a redifferentiation of chloroplasts involving the thylakoidal membrane and lumen. With the purpose to help researchers of concerned disciplines to identify such chloroplasts, we described herein the morphologies of functional and redifferentiating chloroplasts in various members of Tracheophyta. The most obvious sign of redifferentiation is a tremendous swelling of the chloroplast which turns obese. De novo genesis of osmiophilic materials is also characteristic, either as single dots attached to the inner face of the swollen thylakoidal membrane which will yield the tannosomes, or as pearl necklace-shaped structures protruding into the lumen; this last formation can be viewed as a giant tannosome forming finally stromal chlorotannic accretions. Whatever their mode of formation is, tannosomes are expulsed from the chloroplast as shuttles.
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Formation of vacuolar tannin deposits in the chlorophyllous organs of Tracheophyta: from shuttles to accretions
Protoplasma, 2014Co-Authors: Jean-marc Brillouet, Charles Romieu, Marc Lartaud, Elodie Jublanc, Laurent Torregrosa, Chantal CazevieilleAbstract:Most Tracheophyta synthesize-condensed tannins (also called proanthocyanidins), polymers of catechins, which appear in the vacuole as uniformly stained deposits—termed tannin accretions—lining the inner face of the tonoplast. A large body of evidence argues that tannins are formed in recently described thylakoid-derived organelles, the tannosomes, which are packed in membrane-bound shuttles (Brillouet et al. 2013 ); it has been suggested that shuttles agglomerate into tannin accretions. The aim of the study was to describe the ontogenesis of tannin accretions in members of the Tracheophyta. For this purpose, fresh specimens of young tissues from diverse Tracheophyta were cut, gently lacerated in paraformaldehyde, and examined using light, epifluorescence, confocal, and transmission electron microscopy. Fresh samples were also incubated with gelatin-Oregon Green, a fluorescent marker of condensed tannins. Our observations showed that vacuolar accretions (1 → 40 μm), that constitute the typical form of tannin storage in tannin-producing Tracheophyta, are formed by agglomeration (not fusion) of shuttles containing various proportions of chlorophylls and tannins.
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Plasticity of the Tannosome Ontogenesis in the Tracheophyta
Journal of Plant Sciences (Science Publishing Group), 2014Co-Authors: Jean-marc BrillouetAbstract:The tannosome, an organelle producing condensed tannins in the chlorophyllous organs of the Tracheohyta, is formed from the unstacked granal thylakoids by pearling into tiny spheres [1]. Other variants of intraplastidial ontogenesis of the tannosomes were investigated in the Tracheophyta by transmission electron microscopy. The “pearl necklace” model consists in the formation of vaguely ellipsoidal loculi by inflation of the intrathylakoidal lumen in which emerge, bound to the inner face of the lumen, “pear necklace”-shaped suites of osmiophilic spheres (30 nm); once filled with tannins, these loculi can be described as giant tannosomes bound by a single thylakoidal membrane. In the “snail” model, the granal thylakoids whirl upon themselves while pearling tannosomes which remain, in the stroma, aggregated in vaguely spherical osmiophilic structures. While in the former model [1], numerous isolated tannosomes are packed in a shuttle, the aggregated tannosomes (“pearl necklace” and “snail” models) are ejected from the chloroplast by budding into shuttles.
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the tannosome is an organelle forming condensed tannins in the chlorophyllous organs of Tracheophyta
Annals of Botany, 2013Co-Authors: Jean-marc Brillouet, Charles Romieu, Benoit Schoefs, Katalin Solymosi, Veronique Cheynier, Helene Fulcrand, Jean Luc Verdeil, Genevieve ConejeroAbstract:† Background and Aims Condensed tannins (also called proanthocyanidins) are widespread polymers of catechins and are essential for the defence mechanisms of vascular plants (Tracheophyta). A large body of evidence argues for the synthesis of monomeric epicatechin on the cytosolic face of the endoplasmic reticulum and its transport to the vacuole, although the site of its polymerization into tannins remains to be elucidated. The aim of the study was to re-examine the cellular frame of tannin polymerization in various representatives of the Tracheophyta. † Methods Light microscopy epifluorescence, confocal microscopy, transmission electron microscopy (TEM), chemical analysis of tannins following cell fractionation, and immunocytochemistry were used as independent methods on tannin-rich samples from various organs from Cycadophyta, Ginkgophyta, Equisetophyta, Pteridophyta, Coniferophyta and Magnoliophyta. Tissues were fixed in a caffeine‐glutaraldehyde mixture and examined by TEM. Other fresh samples were incubated with primary antibodies against proteins from both chloroplastic envelopes and a thylakoidal chlorophyll-carrying protein; they were also incubated with gelatin‐ Oregon Green, a fluorescent marker of condensed tannins. Coupled spectral analyses of chlorophyll and tannins were carried out by confocal microscopy on fresh tissues and tannin-rich accretions obtained through cell fractionation; chemical analyses of tannins and chlorophylls were also performed on the accretions. † Key Results and Conclusions The presence of the three different chloroplast membranes inside vacuolar accretions that constitute the typical form of tannin storage in vascular plants was established in fresh tissues as well as in purified organelles, using several independent methods. Tannins are polymerized in a new chloroplast-derived organelle, the tannosome. These are formed by pearling of the thylakoids into 30 nm spheres, which are then encapsulated in a tannosome shuttle formed by budding from the chloroplast and bound by a membrane resulting from the fusion of both chloroplast envelopes. The shuttle conveys numerous tannosomes through the cytoplasm towards the vacuole in which it is then incorporated by invagination of the tonoplast. Finally, shuttles bound by a portion of tonoplast aggregate into tannin accretions which are stored in the vacuole. Polymerization of tannins occurs inside the tannosome regardless of the compartment being crossed. A complete sequence of events apparently valid in all studied Tracheophyta is described.
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The tannosome is an organelle forming condensed tannins in the chlorophyllous organs of Tracheophyta.
Annals of Botany, 2013Co-Authors: Jean-marc Brillouet, Charles Romieu, Benoit Schoefs, Katalin Solymosi, Veronique Cheynier, Helene Fulcrand, Jean Luc Verdeil, Genevieve ConejeroAbstract:Background and Aims Condensed tannins (also called proanthocyanidins) are widespread polymers of catechins and are essential for the defence mechanisms of vascular plants (Tracheophyta). A large body of evidence argues for the synthesis of monomeric epicatechin on the cytosolic face of the endoplasmic reticulum and its transport to the vacuole, although the site of its polymerization into tannins remains to be elucidated. The aim of the study was to re-examine the cellular frame of tannin polymerization in various representatives of the Tracheophyta. Methods Light microscopy epifluorescence, confocal microscopy, transmission electron microscopy (TEM), chemical analysis of tannins following cell fractionation, and immunocytochemistry were used as independent methods on tannin-rich samples from various organs from Cycadophyta, Ginkgophyta, Equisetophyta, Pteridophyta, Coniferophyta and Magnoliophyta. Tissues were fixed in a caffeine-glutaraldehyde mixture and examined by TEM. Other fresh samples were incubated with primary antibodies against proteins from both chloroplastic envelopes and a thylakoidal chlorophyll-carrying protein; they were also incubated with gelatin-Oregon Green, a fluorescent marker of condensed tannins. Coupled spectral analyses of chlorophyll and tannins were carried out by confocal microscopy on fresh tissues and tannin-rich accretions obtained through cell fractionation; chemical analyses of tannins and chlorophylls were also performed on the accretions. Key Results and Conclusions The presence of the three different chloroplast membranes inside vacuolar accretions that constitute the typical form of tannin storage in vascular plants was established in fresh tissues as well as in purified organelles, using several independent methods. Tannins are polymerized in a new chloroplast-derived organelle, the tannosome. These are formed by pearling of the thylakoids into 30 nm spheres, which are then encapsulated in a tannosome shuttle formed by budding from the chloroplast and bound by a membrane resulting from the fusion of both chloroplast envelopes. The shuttle conveys numerous tannosomes through the cytoplasm towards the vacuole in which it is then incorporated by invagination of the tonoplast. Finally, shuttles bound by a portion of tonoplast aggregate into tannin accretions which are stored in the vacuole. Polymerization of tannins occurs inside the tannosome regardless of the compartment being crossed. A complete sequence of events apparently valid in all studied Tracheophyta is described.
John Clarke - One of the best experts on this subject based on the ideXlab platform.
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establishing a time scale for plant evolution
New Phytologist, 2011Co-Authors: Rachel C M Warnock, John Clarke, Philip C J DonoghueAbstract:Summary • Plants have utterly transformed the planet, but testing hypotheses of causality requires a reliable time-scale for plant evolution. While clock methods have been extensively developed, less attention has been paid to the correct interpretation and appropriate implementation of fossil data. • We constructed 17 calibrations, consisting of minimum constraints and soft maximum constraints, for divergences between model representatives of the major land plant lineages. Using a data set of seven plastid genes, we performed a cross-validation analysis to determine the consistency of the calibrations. Six molecular clock analyses were then conducted, one with the original calibrations, and others exploring the impact on divergence estimates of changing maxima at basal nodes, and prior probability densities within calibrations. • Cross-validation highlighted Tracheophyta and Euphyllophyta calibrations as inconsistent, either because their soft maxima were overly conservative or because of undetected rate variation. Molecular clock analyses yielded estimates ranging from 568–815 million yr before present (Ma) for crown embryophytes and from 175–240 Ma for crown angiosperms. • We reject both a post-Jurassic origin of angiosperms and a post-Cambrian origin of land plants. Our analyses also suggest that the establishment of the major embryophyte lineages occurred at a much slower tempo than suggested in most previous studies. These conclusions are entirely compatible with current palaeobotanical data, although not necessarily with their interpretation by palaeobotanists.
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Establishing a time‐scale for plant evolution
New Phytologist, 2011Co-Authors: John Clarke, Rachel C M Warnock, Philip C J DonoghueAbstract:Summary • Plants have utterly transformed the planet, but testing hypotheses of causality requires a reliable time-scale for plant evolution. While clock methods have been extensively developed, less attention has been paid to the correct interpretation and appropriate implementation of fossil data. • We constructed 17 calibrations, consisting of minimum constraints and soft maximum constraints, for divergences between model representatives of the major land plant lineages. Using a data set of seven plastid genes, we performed a cross-validation analysis to determine the consistency of the calibrations. Six molecular clock analyses were then conducted, one with the original calibrations, and others exploring the impact on divergence estimates of changing maxima at basal nodes, and prior probability densities within calibrations. • Cross-validation highlighted Tracheophyta and Euphyllophyta calibrations as inconsistent, either because their soft maxima were overly conservative or because of undetected rate variation. Molecular clock analyses yielded estimates ranging from 568–815 million yr before present (Ma) for crown embryophytes and from 175–240 Ma for crown angiosperms. • We reject both a post-Jurassic origin of angiosperms and a post-Cambrian origin of land plants. Our analyses also suggest that the establishment of the major embryophyte lineages occurred at a much slower tempo than suggested in most previous studies. These conclusions are entirely compatible with current palaeobotanical data, although not necessarily with their interpretation by palaeobotanists.
Philip C J Donoghue - One of the best experts on this subject based on the ideXlab platform.
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establishing a time scale for plant evolution
New Phytologist, 2011Co-Authors: Rachel C M Warnock, John Clarke, Philip C J DonoghueAbstract:Summary • Plants have utterly transformed the planet, but testing hypotheses of causality requires a reliable time-scale for plant evolution. While clock methods have been extensively developed, less attention has been paid to the correct interpretation and appropriate implementation of fossil data. • We constructed 17 calibrations, consisting of minimum constraints and soft maximum constraints, for divergences between model representatives of the major land plant lineages. Using a data set of seven plastid genes, we performed a cross-validation analysis to determine the consistency of the calibrations. Six molecular clock analyses were then conducted, one with the original calibrations, and others exploring the impact on divergence estimates of changing maxima at basal nodes, and prior probability densities within calibrations. • Cross-validation highlighted Tracheophyta and Euphyllophyta calibrations as inconsistent, either because their soft maxima were overly conservative or because of undetected rate variation. Molecular clock analyses yielded estimates ranging from 568–815 million yr before present (Ma) for crown embryophytes and from 175–240 Ma for crown angiosperms. • We reject both a post-Jurassic origin of angiosperms and a post-Cambrian origin of land plants. Our analyses also suggest that the establishment of the major embryophyte lineages occurred at a much slower tempo than suggested in most previous studies. These conclusions are entirely compatible with current palaeobotanical data, although not necessarily with their interpretation by palaeobotanists.
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Establishing a time‐scale for plant evolution
New Phytologist, 2011Co-Authors: John Clarke, Rachel C M Warnock, Philip C J DonoghueAbstract:Summary • Plants have utterly transformed the planet, but testing hypotheses of causality requires a reliable time-scale for plant evolution. While clock methods have been extensively developed, less attention has been paid to the correct interpretation and appropriate implementation of fossil data. • We constructed 17 calibrations, consisting of minimum constraints and soft maximum constraints, for divergences between model representatives of the major land plant lineages. Using a data set of seven plastid genes, we performed a cross-validation analysis to determine the consistency of the calibrations. Six molecular clock analyses were then conducted, one with the original calibrations, and others exploring the impact on divergence estimates of changing maxima at basal nodes, and prior probability densities within calibrations. • Cross-validation highlighted Tracheophyta and Euphyllophyta calibrations as inconsistent, either because their soft maxima were overly conservative or because of undetected rate variation. Molecular clock analyses yielded estimates ranging from 568–815 million yr before present (Ma) for crown embryophytes and from 175–240 Ma for crown angiosperms. • We reject both a post-Jurassic origin of angiosperms and a post-Cambrian origin of land plants. Our analyses also suggest that the establishment of the major embryophyte lineages occurred at a much slower tempo than suggested in most previous studies. These conclusions are entirely compatible with current palaeobotanical data, although not necessarily with their interpretation by palaeobotanists.
Wang De-ming - One of the best experts on this subject based on the ideXlab platform.
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A new genus of Early Devonian plants with novel strobilar structures and vegetative appendages from the Posongchong Formation of Yunnan, China
review of palaeobotany and palynology, 2012Co-Authors: Hao Shou-gang, Xue Jin-zhuang, Zhu Xiao, Wang De-mingAbstract:A new plant, Dibracophyton acrovatum gen. et sp. nov., is described from the Lower Devonian (Pragian) Posongchong Formation of Wenshan District, southeastern Yunnan, China. The plant has creeping axes from which arise vegetative and fertile axes. The vegetative axes helically bear lateral dichotomous appendages with curved or round tips. The fertile axes possess terminal strobili with numerous fertile units arranged in irregular helices. Each fertile unit consists of a stalked long-elliptical sporangium, with dehiscence into two equal valves, and two discrete long-ovate bracts covering sporangium from above-below directions. A new genus and species is thus established based on these characters and is temporarily regarded as incertae sedis of Tracheophyta, although it perhaps closes to the barinophytes in affinity. Detailed comparisons with other plants having a similar architecture, i.e., sporangia closely associated with modified vegetative structures, are made. The discovery of D. acrovatum further enriches the composition of the Posongchong flora and demonstrates great morphological disparity of the Early Devonian vascular plants. (C) 2011 Elsevier B.V. All rights reserved.Plant SciencesPaleontologySCI(E)0ARTICLE73-8217
Deming Wang - One of the best experts on this subject based on the ideXlab platform.
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A new genus of Early Devonian plants with novel strobilar structures and vegetative appendages from the Posongchong Formation of Yunnan, China
Review of Palaeobotany and Palynology, 2012Co-Authors: Shougang Hao, Jinzhuang Xue, Xiao Zhu, Deming WangAbstract:Abstract A new plant, Dibracophyton acrovatum gen. et sp. nov., is described from the Lower Devonian (Pragian) Posongchong Formation of Wenshan District, southeastern Yunnan, China. The plant has creeping axes from which arise vegetative and fertile axes. The vegetative axes helically bear lateral dichotomous appendages with curved or round tips. The fertile axes possess terminal strobili with numerous fertile units arranged in irregular helices. Each fertile unit consists of a stalked long-elliptical sporangium, with dehiscence into two equal valves, and two discrete long-ovate bracts covering sporangium from above–below directions. A new genus and species is thus established based on these characters and is temporarily regarded as incertae sedis of Tracheophyta, although it perhaps closes to the barinophytes in affinity. Detailed comparisons with other plants having a similar architecture, i.e., sporangia closely associated with modified vegetative structures, are made. The discovery of D . acrovatum further enriches the composition of the Posongchong flora and demonstrates great morphological disparity of the Early Devonian vascular plants.