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Anis M Limami - One of the best experts on this subject based on the ideXlab platform.

  • aba mediated inhibition of germination is related to the inhibition of genes encoding cell wall biosynthetic and architecture modifying enzymes and structural proteins in medicago truncatula Embryo Axis
    Molecular Plant, 2009
    Co-Authors: Christine Gimenogilles, Eric Lelievre, Laure Viau, Mustafa Malikghulam, Claudie Ricoult, Andreas Niebel, Nathalie Leduc, Anis M Limami
    Abstract:

    Radicle emergence and reserves mobilization are two distinct programmes that are thought to control germination. Both programs are influenced by abscissic acid (ABA) but how this hormone controls seed germination is still poorly known. Phenotypic and microscopic observations of the Embryo Axis of Medicago truncatula during germination in mitotic inhibition condition triggered by 10 μM oryzalin showed that cell division was not required to allow radicle emergence. A suppressive subtractive hybridization showed that more than 10% of up-regulated genes in the Embryo Axis encoded proteins related to cell-wall biosynthesis. The expression of α-expansins, pectin-esterase, xylogucan-endotransglycosidase, cellulose synthase, and extensins was monitored in the Embryo Axis of seeds germinated on water, constant and transitory ABA. These genes were overexpressed before completion of germination in the control and strongly inhibited by ABA. The expression was re-established in the ABA transitory-treatment after the seeds were transferred back on water and proceeded to germination. This proves these genes as contributors to the completion of germination and strengthen the idea that cell-wall loosening and remodeling in relation to cell expansion in the Embryo Axis is a determinant feature in germination. Our results also showed that ABA controls germination through the control of radicle emergence, namely by inhibiting cell-wall loosening and expansion.

  • a gene encoding a protein with a proline rich domain mtpprd1 revealed by suppressive subtractive hybridization ssh is specifically expressed in the medicago truncatula Embryo Axis during germination
    Journal of Experimental Botany, 2005
    Co-Authors: Sophie Bouton, Eric Lelievre, Laure Viau, Anis M Limami
    Abstract:

    A gene MtPPRDI, encoding a protein of 132 amino acids containing a proline-rich domain (PRD), has been revealed by suppressive subtractive hybridization (SSH) with two mRNA populations of Embryo axes harvested immediately before and after radicle emer gence. Although at the protein level MtPPRDI showed low homology with plant lipid transfer proteins (LTPs), it did exhibit the eight cysteine residues conserved in all plant LTPs, a characteristic signature that allows the formation of a hydrophobic cavity adapted for loading hydrophobic molecules. Expression studies of MtPPRDI have been carried out by quantitative real time RT-PCR throughout germination and post-germination processes in control seeds and seeds in which germination was delayed by abscisic acid (ABA) or the glutamine synthetase inhibitor methionine sulphoximine (MSX) treatments. The results showed that MtPPRDI expres sion is developmental^ regulated, induced in the Embryo Axis immediately before radicle emergence, reaches its maximum expression and declines during the early post-germination phase. Organ specificity studies showed that, except for a low and probably constitutive expression in roots, MtPPRDI is specifi cally expressed in the Embryo Axis. Based on both experimental and in silico studies several putative roles are proposed for MtPPRDI in Medicago trunca tula, this protein can intervene (i) as an LTP in mem brane biogenesis and regulation of the intracellular fatty acid pool by binding and transferring fatty acids and phospholipids between membranes, (ii) in the control of a developmental process specific to late germination and to early phases of post-germination, and (iii) and/or pathogen defence.

  • Respective roles of the glutamine synthetase/glutamate synthase cycle and glutamate dehydrogenase in ammonium and amino acid metabolism during germination and post-germinative growth in the model legume Medicago truncatula
    Planta, 2004
    Co-Authors: Gaëlle Glevarec, Sophie Bouton, Emmanuel Jaspard, Marie-thérèse Riou, Jean-bernard Cliquet, Akira Suzuki, Anis M Limami
    Abstract:

    Our objective was to determine the respective roles of the couple glutamine synthetase/glutamate synthase (GS/GOGAT) and glutamate dehydrogenase (GDH) in ammonium and amino acid metabolism during germination and post-germinative growth in the model legume Medicago truncatula Gaertn. For this aim, amino acids were analyzed by HPLC and changes in gene expression of several enzymes involved in N and C metabolism were studied by real-time quantitative reverse transcription–polymerase chain reaction. Among the enzymes studied, GDH showed the highest increase in gene expression (80-fold), specifically in the Embryo Axis and concomitant with the increase in ammonium content during post-germinative growth. In cotyledons, GDH gene expression was very low. Although in vitro GDH aminating activity was several times higher than its deaminating activity, in vivo 15NH4 incorporation into amino acids was completely inhibited by methionine sulfoximine, a GS inhibitor, indicating that GDH is not involved in ammonium assimilation/detoxification. Changes in the expressions of GS and GOGAT isoforms revealed that GS1b (EC 6.3.1.2) in concert with NADH-dependent GOGAT (EC 1.4.1.14) constitute the major route of assimilation of ammonium derived from reserve mobilization and glutamic acid/glutamine synthesis in germinating M. truncatula seeds. However, during post-germinative growth, although germination was held in darkness, expression of GS2 and Fd-GOGAT (EC 1.4.7.1) increased and expression of GS1b decreased in cotyledons but not in the Embryo Axis. 2-Oxoglutarate, the substrate of the transamination reaction, was provided by the cytosolic isoform of isocitrate dehydrogenase (EC 1.1.1.42). We suggest that GDH during post-germinative growth, specifically in the developing Embryo Axis, contributes to ammonium delivery to GS for glutamine synthesis in the absence of primary NO3− assimilation. Interestingly, this reaction also produces reducing power (NADH) in organs deprived of photosynthesis.

Lorenza Bellani - One of the best experts on this subject based on the ideXlab platform.

  • Effects of ageing on peroxidase activity and localization in radish (Raphanus sativus L.) seeds.
    European Journal of Histochemistry, 2010
    Co-Authors: Anna Scialabba, Lorenza Bellani, A. Dell'aquila
    Abstract:

    Peroxidase activity was assayed in crude extracts of integument, cotyledons and Embryo Axis of radish seeds, deteriorated under accelerated ageing conditions. Over five days of ageing, in which germination decreased from 100 to 52%, the enzyme activity in integument was higher than that in other seed parts, increasing in the first days of ageing and then decreasing sharply in extremely aged seeds. Polyacrylamide gel electrophoresis analysis showed four peroxidase isoenzymes with MM of 98, 52.5, 32.8 and 29.5 kDa in the Embryo Axis of unaged seeds, and only the 32.8 and 29.5 kDa MM isoforms in the integument and cotyledons. In these parts of the seed, only the 29.5 kDa MM isoenzyme increased in activity in early days of ageing and decreased thereafter. In the Embryo Axis, the 29.5 kDa MM isoenzyme activity increased slowly in the first day of ageing, while the 98 and 52.5 kDa MM isoenzyme activities disappeared. A cytochemical localization of peroxidase activity in the various tissues showed that main differences between unaged and extremely aged seeds occurred in the Embryo Axis.

  • ultrastructural and biochemical investigations of protein mobilization of mucuna pruriens l dc cotyledons and Embryo Axis
    Protoplasma, 2010
    Co-Authors: Simonetta Muccifora, Roberto Guerranti, Chiara Muzzi, Nnadozies S Hopeonyekwere, Roberto Pagani, Roberto Leoncini, Lorenza Bellani
    Abstract:

    The mobilization of storage reserves, with particular emphasis on storage proteins of Mucuna pruriens (L.) DC., cotyledons, and Embryo was investigated from the ultrastructural and biochemical points of view. Proteins and starch were the two main storage substances in cotyledons, and proteins and lipids were the main ones in the Embryo. Embryo protein bodies were smaller and fewer in number than those of cotyledons. Structural and ultrastructural data determined between 24 and 48 h after imbibition and between 48 and 72 h after imbibition, the end of significant Embryo and cotyledon protein mobilization, respectively, indicating more precocious storage protein mobilization in the Axis than cotyledons. Moreover, storage protein mobilization in Embryo and cotyledons occurred before the end of germination. Water soluble proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, producing 29 bands with molecular weights from 14 to 90 KDa. Embryo extract contained more proteins than cotyledon extract, contained seven characteristic bands, and showed a higher variability of the optical density trend than cotyledon.

  • Differences in the activity and distribution of peroxidases from three different portions of germinating Brassica oleracea seeds.
    Physiologia Plantarum, 2002
    Co-Authors: Lorenza Bellani, Massimo Guarnieri, Anna Scialabba
    Abstract:

    Peroxidase (POD, EC 1.11.1.7) activity, cellular localization and isozyme patterns were investigated in the seed integument, cotyledon and Embryo Axis of Brassica oleracea cv. Cappuccio during pregermination and seedling growth. Seeds started to germinate after 24 h of imbibition. POD activity was localized in the pigmented layer of the integument and in procambial strands of the cotyledon and Embryo Axis in the first 24 h of imbibition. It was localized in the integumental cells of palisade, pigmented and aleurone layers and in epidermal, meristematic, procambial cells and xylem elements of the root and hypocotyl after 48 h of imbibition. POD activity increased during germination and early seedling growth: in the integument, it reached a maximum value after 72 h of imbibition, in the Embryo Axis and cotyledons, it increased up to 144 h of imbibition. The increase in peroxidase activity was accompanied by the appearance of new isozymes correlated with the development of seedling tissues. The isozyme profile was characterized by nine peroxidases: isoperoxidase of 50 kDa peculiar to integuments, that of 150 kDa to cotyledons and that of 82 kDa to the Embryo Axis. During pregerminative phase isozymes of 84 kDa were detected in the integument and cotyledons, of 48.5 kDa in the Embryo Axis. After germination, peroxidase activity and the complexity of the isozyme pattern increased, suggesting that they play a relevant role after rupture of the integument.

Mercedes Muzquiz - One of the best experts on this subject based on the ideXlab platform.

  • Content and distribution of protein, sugars and inositol phosphates during the germination and seedling growth of two cultivars of Vicia faba
    Journal of Food Composition and Analysis, 2011
    Co-Authors: C. Goyoaga, Carmen Burbano, Carmen Cuadrado, A. Varela, Eva Guillamón, Mercedes M. Pedrosa, C. Romero, Mercedes Muzquiz
    Abstract:

    Abstract The storage protein profile of seed cotyledons and the content of soluble sugar and inositol phosphates in the cotyledons and Embryo Axis during germination and seedling growth of two cultivars of faba bean, Vicia faba (Alameda and Brocal), were studied because little is known of the precise distribution of these compounds in the different parts of faba bean seeds. Among storage protein fractions, the legumins showed the greatest mobilization by hydrolysis 3 days after imbibition (DAI). In both bean cultivars, the raffinose family oligosaccharides (RFO s ) content, mainly present in the cotyledons, were drastically reduced by 2 DAI. However, total sugars concentration in the Embryo Axis at 9 DAI had increased more than 20-fold. Germination and seedling growth reduced the phytate content of the cotyledon (8–14%) and in the Embryo Axis (3–7%). A knowledge of the mechanism and timing of mobilization of each storage protein fraction, oligosaccharides and myo-inositol phosphates could help to establish and even rationally modify the nutritional relevance of these compounds in legume seed.

  • Content and distribution of vicine, convicine and l -DOPA during germination and seedling growth of two Vicia faba L. varieties
    European Food Research and Technology, 2008
    Co-Authors: C. Goyoaga, Carmen Burbano, Carmen Cuadrado, A. Varela, Eva Guillamón, Mercedes M. Pedrosa, Mercedes Muzquiz
    Abstract:

    This work examined the content and distribution of the pyrimidine glucosides vicine and convicine, and the nonproteic amino acid l-DOPA in cotyledons and Embryo axes along the germination and seedling growth of Vicia faba L. vars. Alameda and Brocal. The behaviour of these compounds was similar in both varieties. Vicine and convicine, implicated in favism disease, slowly declined in cotyledons. In Embryo Axis, vicine levels were sharply reduced and convicine amount was slightly increased as assay progressed. Total pyrimidine glucosides remained unchanged in the whole plant during the study. l-DOPA only appeared in the Embryo Axis of V. faba seeds and the highest content was observed in Brocal variety at 6 DAI (days after imbibition). The information provided in this study could be valuable for a possible role of Embryo Axis, rich in l-DOPA, for the treatment of Parkinson’s disease and also as a choice ingredient for functional foods or as nutraceutical.

Dennis M Reinecke - One of the best experts on this subject based on the ideXlab platform.

  • developmental and Embryo Axis regulation of gibberellin biosynthesis during germination and young seedling growth of pea
    Plant Physiology, 2006
    Co-Authors: Belay T Ayele, Jocelyn A Ozga, Leonid V Kurepin, Dennis M Reinecke
    Abstract:

    The expression patterns of five genes (PsGA20ox1, PsGA20ox2, PsGA3ox1, PsGA2ox1, and PsGA2ox2) encoding five regulatory gibberellin (GA) biosynthesis enzymes (two GA 20-oxidases, a GA 3β-hydroxylase, and two GA 2β-hydroxylases) were examined to gain insight into how these genes coordinate GA biosynthesis during germination and early postgermination stages of the large-seeded dicotyledonous plant pea (Pisum sativum). At the time the developing Embryo fills the seed coat, high mRNA levels of PsGA20ox2 (primarily responsible for conversion of C20-GAs to GA20), PsGA2ox1 (primarily responsible for conversion of GA20 to GA29), and PsGA2ox2 (primarily responsible for conversion of GA1 to GA8) were detected in the seeds, along with high GA20 and GA29 levels, the enzymatic products of these genes. Embryo maturation was accompanied by a large reduction in PsGA20ox2 and PsGA2ox1 mRNA and lower GA20 and GA29 levels. However, PsGA2ox2 transcripts remained high. Following seed imbibition, GA20 levels in the cotyledons decreased, while PsGA3ox1 mRNA and GA1 levels increased, implying that GA20 was being used for de novo synthesis of GA1. The presence of the Embryo Axis was required for stimulation of cotyledonary GA1 synthesis at the mRNA and enzyme activity levels. As the Embryo Axis doubled in size, PsGA20ox1 and PsGA3ox1 transcripts increased, both GA1 and GA8 were detectable, PsGA2ox2 transcripts decreased, and PsGA2ox1 transcripts remained low. Cotyledonary-, root-, and shoot-specific expression of these GA biosynthesis genes and the resultant endogenous GA profiles support a key role for de novo GA biosynthesis in each organ during germination and early seedling growth of pea.

Thomas Laux - One of the best experts on this subject based on the ideXlab platform.

  • The origin of the plant body Axis.
    Current Opinion in Plant Biology, 2012
    Co-Authors: Minako Ueda, Thomas Laux
    Abstract:

    During Embryogenesis, the basic body plan of an organism develops from a unicellular zygote. In most flowering plants, the polar zygote divides asymmetrically, making visible the apical–basal Axis in the early Embryo. The molecular mechanisms governing how the zygote polarizes and how this polarity is linked to Embryo Axis formation have been obscure, mainly owing to the difficulties to access the zygote that is deeply embedded in the maternal tissue. In this review, we summarize recent findings identifying key regulators in Arabidopsis and developing novel approaches in various plant species, which altogether set the stage for unraveling Embryo Axis formation.

  • The origin of the plant body Axis
    Current Opinion in Plant Biology, 2012
    Co-Authors: Minako Ueda, Thomas Laux
    Abstract:

    During Embryogenesis, the basic body plan of an organism develops from a unicellular zygote. In most flowering plants, the polar zygote divides asymmetrically, making visible the apical-basal Axis in the early Embryo. The molecular mechanisms governing how the zygote polarizes and how this polarity is linked to Embryo Axis formation have been obscure, mainly owing to the difficulties to access the zygote that is deeply embedded in the maternal tissue. In this review, we summarize recent findings identifying key regulators in Arabidopsis and developing novel approaches in various plant species, which altogether set the stage for unraveling Embryo Axis formation. © 2012 Elsevier Ltd.

  • the asymmetric division of the arabidopsis zygote from cell polarity to an Embryo Axis
    Sexual Plant Reproduction, 2011
    Co-Authors: Zhongjuan Zhang, Thomas Laux
    Abstract:

    During plant Embryogenesis, a simple body plan consisting of shoot and root meristem that are connected by the Embryo Axis is set up by the first few rounds of cell divisions after fertilization. PostEmbryonically, the elaborate architecture of plants is created from stem cell populations of both meristems. Here, we address how the main Axis (apical-basal) of the plant Embryo is established from the single-celled zygote and the role that the asymmetric division of the zygote plays in this process. We will mainly draw on examples from the model plant Arabidopsis, for which several key regulators have been identified during the last years.