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1.
Tree Physiol ; 35(6): 678-90, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25877768

RESUMO

A reproducible procedure for induction of somatic embryogenesis (SE) from adult trees of Eucalyptus globulus Labill. and the hybrid E. saligna Smith × E. maidenii has been developed for the first time. Somatic embryos were obtained from both shoot apex and leaf explants of all three genotypes evaluated, although embryogenic frequencies were significantly influenced by the species/genotype, auxin and explant type. Picloram was more efficient for somatic embryo induction than naphthaleneacetic acid (NAA), with the highest frequency of induction being obtained in Murashige and Skoog medium containing 40 µM picloram and 40 mg l(-1) gum Arabic, in which 64% of the shoot apex explants and 68.8% of the leaf explants yielded somatic embryos. The embryogenic response of the hybrid was higher than that of the E. globulus, especially when NAA was used. The cultures initiated on picloram-containing medium consisted of nodular embryogenic structures surrounded by a mucilaginous coating layer that emerged from a watery callus developed from the initial explants. Cotyledonary somatic embryos were differentiated after subculture of these nodular embryogenic structures on a medium lacking plant growth regulators. Histological analysis confirmed the bipolar organization of the somatic embryos, with shoot and root meristems and closed procambial tissue that bifurcated into small cotyledons. The root pole was more differentiated than the shoot pole, which appeared to be formed by a few meristematic layers. Maintenance of the embryogenic lines by secondary SE was attained by subculturing individual cotyledonary embryos or small clusters of globular and torpedo embryos on medium with 16.11 µM NAA at 4- to 5-week intervals. Somatic embryos converted into plantlets after being transferred to liquid germination medium although plant regeneration remained poor.


Assuntos
Cruzamentos Genéticos , Eucalyptus/embriologia , Brotos de Planta/crescimento & desenvolvimento , Técnicas de Embriogênese Somática de Plantas/métodos , Árvores/embriologia , Eucalyptus/efeitos dos fármacos , Genótipo , Morfogênese/efeitos dos fármacos , Ácidos Naftalenoacéticos/farmacologia , Picloram/farmacologia , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/crescimento & desenvolvimento , Brotos de Planta/efeitos dos fármacos , Regeneração/efeitos dos fármacos , Sementes/efeitos dos fármacos , Sementes/embriologia , Árvores/efeitos dos fármacos
2.
Cryo Letters ; 34(1): 30-9, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23435708

RESUMO

Empirical testing of protocols and fundamental investigations are the approaches usually applied to study germplasm storage recalcitrance in temperate plants. However, they can fall short of practicable solutions, even after exhaustive experimentation, and the generation of negative survival data makes it difficult to plan further investigations. Picea sitchensis somatic embryos are amenable to cryopreservation whereas in vitro shoot meristems, although able to survive, are incapable of sustained recovery. Differential Scanning Calorimetry (DSC) revealed that these disparate responses could not be attributed to biophysical factors. A model is presented hypothesising that in some cases life cycle adaptations (cold hardening, dormancy) may have opposing influences on survival causing delayed-onset, cryogenically-induced loss of viability in temperate tree species.


Assuntos
Meristema/fisiologia , Picea/embriologia , Árvores/embriologia , Vitrificação , Aclimatação , Varredura Diferencial de Calorimetria , Criopreservação , Modelos Biológicos , Picea/fisiologia , Árvores/fisiologia
3.
Oecologia ; 172(3): 857-67, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23229391

RESUMO

Positive density-dependent seed and seedling predation, where herbivores selectively eat seeds or seedlings of common species, is thought to play a major role in creating and maintaining plant community diversity. However, many herbivores and seed predators are known to exhibit preferences for rare foods, which could lead to negative density-dependent predation. In this study, we first demonstrate the occurrence of increased predation of locally rare tree species by a widespread group of insular seed and seedling predators, land crabs. We then build computer simulations based on these empirical data to examine the effects of such predation on diversity patterns. Simulations show that herbivore preferences for locally rare species are likely to drive scale-dependent effects on plant community diversity: at small scales these foraging patterns decrease plant community diversity via the selective consumption of rare plant species, while at the landscape level they should increase diversity, at least for short periods, by promoting clustered local dominance of a variety of species. Finally, we compared observed patterns of plant diversity at the site to those obtained via computer simulations, and found that diversity patterns generated under simulations were highly consistent with observed diversity patterns. We posit that preference for rare species by herbivores may be prevalent in low- or moderate-diversity systems, and that these effects may help explain diversity patterns across different spatial scales in such ecosystems.


Assuntos
Biodiversidade , Crustáceos/fisiologia , Sementes , Árvores/classificação , Animais , Herbivoria , Árvores/embriologia , Árvores/crescimento & desenvolvimento
4.
Sex Plant Reprod ; 24(4): 283-96, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21644002

RESUMO

Control of female parthenogenetic apomixis and androsporogenesis of Douglas-fir embryonal initials was studied using an experimental culture system in which changes in growth condition can mediate changes in cell identity and outcomes. This culture system constitutes an artificial sporangium in which myriad culture conditions can be simulated and should be applicable for research on a variety of gymnosperms. In this study, embryonal initials from developing seeds from two Douglas-fir trees were rescued and became reprogrammed for female parthenogenetic apomixis (fPA) and parthenogenetic androsporogenesis (mPA). Female PA was initiated by endomitosis forming a binucleate cell with a diploid egg-equivalent and an apoptotic ventral canal nucleus in an archegonial tube. Egg-equivalent nuclei formed cells (parthenotes) that were discharged into an aqueous culture medium. Parthenotes developed axial tiers atypical of early embryogenesis in seeds. Earlier in the year, androsporangial tubes were parthenogenetically differentiated and released monads, dyads, triads, and tetrads into the culture medium. Spores showed chromosomal aberrations. PA demonstrated a temporal separation in gender expression (dichogamy). Embryonal initials brought forward and by-passed the long juvenile phases normally needed for cells to develop into trees and express reproductive maturity. Expressions of fPA and mPA indicated that the specialized culture flasks served as an artificial sporangium (AS). Awareness is raised for the value of an AS for research in gymnosperm life cycles and as a teaching and research laboratory.


Assuntos
Apomixia , Partenogênese , Pseudotsuga/fisiologia , Esporângios/fisiologia , Árvores/fisiologia , Pseudotsuga/embriologia , Pseudotsuga/genética , Esporângios/embriologia , Esporângios/genética , Esporos/genética , Esporos/crescimento & desenvolvimento , Técnicas de Cultura de Tecidos , Árvores/embriologia , Árvores/genética
5.
Tree Physiol ; 31(5): 539-54, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21636694

RESUMO

The focus of the current project was to establish somatic embryogenesis protocols for the tropical pine species Pinus oocarpa using immature zygotic embryos (ZEs) as explants. Somatic embryogenesis is best supported by mimicking natural seed-embryo developmental conditions, through a tissue culture medium formulation based on the mineral content of the seed nutritive tissue [megagametophyte (MG)]. A novel culture medium (P. oocarpa medium, PO) was tested in combination with different plant growth regulator (PGR) concentrations and compared with standard Pinus taeda media for the initiation of somatic embryogenesis from immature ZEs of P. oocarpa. Immature MGs containing immature ZEs of two mother trees were used with 12 and 8% extrusion rates for mother tree genotypes 3 and 5, respectively. In both mother trees the percentage capture was 2%. Multiplication of two captured cell lines (T5C2S01 and T5C1S12) was improved by lowering the concentrations of PGRs to 2.5 µM each 2,4-dichlorophenoxyacetic acid and abscisic acid (ABA) plus 1.0 µM each 6-benzylaminopurine and kinetin. Mature somatic embryos formed on 40 µM ABA, 6% (w/v) maltose, 12% (w/v) PEG 8000 and 0.6% (w/v) Phytagel. While PO medium appeared suboptimal for somatic embryo induction, it did exhibit potential for enhanced culture proliferation and subsequent improved maturation with cell line T5C2S01, where microscopic analysis revealed better embryo morphology on PO medium than on 1250 medium. However, this enhancement was not observed with cell line T5C1S12. Germination was preceded by partial desiccation for a period of 2-3 weeks before transferring the embryos to germination medium. Germination was observed after 7 days under low light, and apical primordia slowly expanded after transfer to ex vitro conditions. To our knowledge, this is the first report on the production of somatic seedlings in P. oocarpa.


Assuntos
Pinus/embriologia , Técnicas de Embriogênese Somática de Plantas/métodos , Árvores/embriologia , Ácido 2,4-Diclorofenoxiacético , Ácido Abscísico , Compostos de Benzil , Meios de Cultura , Herbicidas , Óvulo Vegetal/crescimento & desenvolvimento , Pinus/crescimento & desenvolvimento , Pinus/metabolismo , Reguladores de Crescimento de Plantas , Purinas , Árvores/crescimento & desenvolvimento , Árvores/metabolismo
6.
Environ Sci Technol ; 44(10): 4019-25, 2010 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-20429594

RESUMO

Chinese tallow tree (TT) seeds are a rich source of lipids and have the potential to be a biodiesel feedstock, but currently, its invasive nature does not favor large scale cultivation. Being a nonfood material, they have many advantages over conventional crops that are used for biodiesel production. The purpose of this study was to determine optimal oil extraction parameters in a batch-type and laboratory scale continuous-flow microwave system to obtain maximum oil recovery from whole TT seeds using ethanol as the extracting solvent. For the batch system, extractions were carried out for different time-temperature combinations ranging from 60 to 120 degrees C for up to 20 min. The batch system was modified for continuous extractions, which were carried out at 50, 60, and 73 degrees C and maintained for various residence times of up to 20 min. Control runs were performed under similar extraction conditions and the results compared well, especially when accounting for extremely short extraction times (minutes vs hours). Maximum yields of 35.32% and 32.51% (by weight of dry mass) were obtained for the continuous and batch process, respectively. The major advantage of microwave assisted solvent extraction is the reduced time of extraction required to obtain total recoverable lipids, with corresponding reduction in energy consumption costs per unit of lipid extracted. This study indicates that microwave extraction using ethanol as a solvent can be used as a viable alternative to conventional lipid extraction techniques for TT seeds.


Assuntos
Biocombustíveis , Micro-Ondas , Sementes , Árvores/embriologia
7.
Sex Plant Reprod ; 23(2): 95-103, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20084524

RESUMO

Rhizophora mucronata Lam. is a tropical mangrove with semi-viviparous (cotyledon body protrusion before shedding), non-quiescent and non-desiccating (recalcitrant) seeds. As recalcitrance has been thought to relate to the absence of desiccation-related proteins such as dehydrins, we for the first time systematically described and classified embryogenesis in R. mucronata and assessed the presence of dehydrin-like proteins. Embryogenesis largely follows the classic pattern till stage eight, the torpedo stage, with the formation of a cotyledonary body. Ovule and embryo express radical adaptations to semi-vivipary in the saline environment: (1) A large, highly vacuolated and persistent endosperm without noticeable food reserves that envelopes the developing embryo. (2) Absence of vascular tissue connections between embryo and maternal tissue, but, instead, transfer layers in between endosperm and integument and endosperm and embryo. Dehydrin-like proteins (55-65 kDa) were detected by the Western analysis, in the ovules till stage 10 when the integuments are dehisced. An additional 50 kDa band was detected at stages 6-8. Together these results suggest a continuous flow of water with nutrients from the integument via the endosperm to the embryo, circumventing the vascular route and probably suppressing the initially induced dehydrin expression.


Assuntos
Endosperma/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Plantas/genética , Rhizophoraceae/embriologia , Endosperma/embriologia , Endosperma/genética , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/metabolismo , Rhizophoraceae/genética , Rhizophoraceae/metabolismo , Árvores/embriologia , Árvores/genética , Árvores/metabolismo
8.
Oecologia ; 159(2): 389-400, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19018573

RESUMO

Seed dispersal patterns were studied in a north-western Spain temperate forest community to assess the performances of alternative dispersal kernels during two years with ecologically contrasting scenarios; a non-mast year, and a mast year of the dominant canopy species, beech Fagus sylvatica. Dispersal kernels were fitted under a Bayesian modeling framework. Both simple and mixture kernels were considered for the five more abundant tree species (Corylus avellana, Crataegus monogyna, F. sylvatica, Ilex aquifolium and Taxus baccata). Mixture kernels provided a better fit for almost all species, and the log-normal performed best for T. baccata. No relationship between dispersal syndromes and the best dispersal kernel function emerged. However, we found temporal changes in the shape of the dispersal kernels that seemed to be related to variation in relative fruit production among species and the resulting changes in the responses of dispersal vectors. This reveals a potential role for disperser-mediated indirect effects in terms of introducing temporal variation in species spread. In this sense, our results highlight the need to consider single species seed dispersal as a community process.


Assuntos
Sementes , Árvores/embriologia , Modelos Teóricos
9.
Development ; 135(23): 3813-6, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18997109

RESUMO

The biannual FASEB summer research conference ;Mechanisms in Plant Development' was recently held in Saxtons River, Vermont and was organised by Neelima Sinha and Cris Kuhlemeier. Although most of the work discussed at the meeting concentrated on developmental mechanisms and on studies in Arabidopsis and maize, the meeting also emphasised the importance of variation between species and the elaboration of a broader range of model systems.


Assuntos
Variação Genética , Plantas/embriologia , Árvores/embriologia , Evolução Biológica , Padronização Corporal , Células Germinativas , Ácidos Indolacéticos/metabolismo , Folhas de Planta/embriologia , Plantas/genética , RNA de Plantas/metabolismo , Vermont , Madeira
10.
Ann Bot ; 102(5): 865-75, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18757880

RESUMO

BACKGROUND AND AIMS: The optimal period for seedling emergence depends on factors such as habitat preference, life cycle and geographical distribution. This research was performed to clarify the role of temperature in regulating processes leading to seedling emergence of the European continental Scilla bifolia and the Atlantic Narcissus pseudonarcissus and Hyacinthoides non-scripta. METHODS: Experiments in natural conditions were performed to examine the phenology of embryo growth, seed germination in the soil and seedling emergence. Effects of temperature conditions on embryo growth, seed germination, seedling growth and leaf formation were studied in temperature-controlled incubators. KEY RESULTS: In nature, embryo growth of all three species was initiated from the moment the seeds were dispersed in spring and continued during summer. A sequence of high temperature followed by a lower temperature was required to complete embryo growth and initiate germination. Seeds of H. non-scripta and N. pseudonarcissus germinated in autumn once they attained the critical E:S ratio, while seeds of S. bifolia started germinating when temperatures were low in winter. Seedlings developed normally, but slowly, only when placed in low temperature conditions (5 or 10 degrees C), resulting in a time lag between the moment of radicle protrusion and seedling emergence in the field. CONCLUSIONS: A continuous development of the embryo and seedlings of the three species was observed from the moment the seeds were dispersed until seedlings emerged. A sequence of high summer temperatures followed by decreasing autumn and winter temperatures was required for all developmental processes to be completed. Although a time lag occurs between radicle protrusion and seedling emergence, the term 'epicotyl dormancy' does not apply here, due to the absence of a period of developmental arrest. Timing of first seedling emergence differed between the three species and could be related to differences in geographical distribution.


Assuntos
Germinação/fisiologia , Liliaceae/embriologia , Estações do Ano , Plântula/crescimento & desenvolvimento , Sementes/crescimento & desenvolvimento , Temperatura , Árvores/embriologia , Folhas de Planta/crescimento & desenvolvimento , Fatores de Tempo
11.
Plant Cell Rep ; 27(6): 1093-101, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-18317772

RESUMO

A reproducible protocol for somatic embryogenesis (SE) induction in Eucalyptus globulus from mature zygotic embryos is available since 2002. However, for the use of SE in tree breeding programs, the frequency of SE initiation needs to be improved and controlled, and this was investigated in 13 open-pollinated (OP) families over three consecutive years. A diallel mating design with five parent trees was used to study genetic control of SE induction. Results showed that SE induction varies across E. globulus families and over the years of seed production tested. Somatic embryogenesis was initiated on explants from 84% of the OP families tested in 2002 and 100% of the families tested in 2003 and 2004. The year 2003 gave best results for percentage of induction and total number of somatic embryos produced. Results concerning genetic control showed that SE induction is under the control of additive genetic effects, as 22.0% of variation in SE initiation was due to general combining ability (GCA) effect, whereas 6.4% was due to maternal effects. Neither specific combining ability (SCA) nor reciprocal effects were significant.


Assuntos
Eucalyptus/embriologia , Eucalyptus/genética , Regulação da Expressão Gênica de Plantas , Análise de Variância , Cruzamento , Cruzamentos Genéticos , Variação Genética , Genótipo , Polinização/genética , Árvores/embriologia , Árvores/genética
12.
J Chem Ecol ; 33(12): 2254-65, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18026796

RESUMO

Hinoki-asunaro (Thujopsis dolabrata Sieb. et Zucc. var. hondai Makino) is a tree endemic in Japan whose seeds produce several terpenoids. We hypothesized that antifungal compounds in seeds might select for fungi on the root surfaces of T. dolabrata var. hondai seedlings. We examined seed and soil fungi, their sensitivity to methanol extracts of the seeds, the fungi on root surfaces of seedlings grown in Kanuma pumice (a model mineral soil) and nursery soil, and the frequency at which each fungus was detected on the seedling root surface. We calculated correlation coefficients between fungal detection frequency on root surfaces and fungal sensitivity to seed extracts. We also isolated from the seeds the antifungal compound totarol that selected for fungi on root surfaces. Species of Alternaria, Cladosporium, Pestalotiopsis, and Phomopsis were the most frequently isolated fungi from seeds. Mortierella and Mucor were the dominant fungi isolated from Kanuma pumice, whereas Umbelopsis and Trichoderma were the main fungi isolated from nursery soil. Alternaria, Cladosporium, Mortierella, Pestalotiopsis, and Phomopsis were the dominant fungi isolated from root surfaces of seedlings grown in Kanuma pumice, and Alternaria, Cladosporium, Pestalotiopsis, Phomopsis, and Trichoderma were the main root-surface fungi isolated from seedlings grown in nursery soil. The fungal detection frequencies on root surfaces in both soils were significantly and negatively correlated with fungal sensitivity to the seed extract. A similar correlation was found between the fungal detection frequency on root surfaces and fungal sensitivity to totarol. We conclude that totarol is one factor that selects for fungi on root surfaces of T. dolabrata var. hondai in the early growth stage.


Assuntos
Antifúngicos/farmacologia , Diterpenos/farmacologia , Fungos/efeitos dos fármacos , Raízes de Plantas/microbiologia , Sementes/química , Árvores/química , Abietanos , Antifúngicos/isolamento & purificação , Diterpenos/isolamento & purificação , Fungos/classificação , Árvores/embriologia
13.
Eur J Biochem ; 268(22): 5723-33, 2001 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-11722556

RESUMO

Cinnamomin is a new type II ribosome-inactivating protein (RIP). Its A-chain exhibits RNA N-glycosidase activity to inactivate the ribosome and thus inhibit protein synthesis, whereas the glycosylated B-chain is a lectin. The primary structure of cinnamomin, which exhibits approximately 55% identity with those of ricin and abrin, was deduced from the nucleotide sequences of cDNAs of cinnamomin A- and B-chains. It is composed of a total of 549 amino-acid residues: 271 residues in the A-chain, a 14-residue linker and 264 residues in the B-chain. To explore its biological function, the cinnamomin A-chain was expressed in Escherichia coli with a yield of 100 mg per L of culture, and purified through two-step column chromatography. After renaturation, the recovery of the enzyme activity of the expressed A-chain was 80% of that of native A-chain. Based on the modeling of the three-dimensional structure of the A-chain, the functional roles of five amino acids and the only cysteine residues were investigated by site-directed mutagenesis or chemical modification. The conserved single mutation of the five amino-acid residues led to 8-50-fold losses of enzymatic activity, suggesting that these residues were crucial for maintaining the RNA N-glycosidase activity of the A-chain. Most interestingly, the strong electric charge introduced at the position of the single cysteine in A-chain seemed to play a role in enzyme/substrate binding.


Assuntos
Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Proteínas/química , Proteínas/metabolismo , Sementes/química , Árvores/embriologia , Proteínas de Algas , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , DNA Complementar , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Proteínas de Plantas/genética , Conformação Proteica , Proteínas/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteínas Inativadoras de Ribossomos Tipo 2 , Ribossomos , Homologia de Sequência de Aminoácidos , Relação Estrutura-Atividade
14.
Cryobiology ; 42(3): 196-206, 2001 May.
Artigo em Inglês | MEDLINE | ID: mdl-11578119

RESUMO

This study investigated the interactions among water content, rapid (nonequilibrium) cooling to -196 degrees C using isopentane or subcooled nitrogen, and survival of embryonic axes of Aesculus hippocastanum. Average cooling rates in either cryogen did not exceed 60 degrees C s(-1) for axes containing more than 1.0 g H(2)O g(-1)dw (g g(-1)). Partial dehydration below 0.5 g gg(-1) facilitated faster cooling, averaging about 200 and 580 degrees C s(-1) in subcooled nitrogen and isopentane, respectively. The combination of partial drying and rapid cooling led to increased survival and reduced cellular damage in axes. Electrolyte leakage was 10-fold higher from fully hydrated axes cooled in either cryogen than from control axes that were not cooled. Drying of axes to 0.5 g g(-1), reduced electrolyte leakage of cryopreserved axes to levels similar to those of control material. Axis survival was assayed by germination in vitro. Axes with water contents greater than 1.0 g g(-1), did not survive cryogenic cooling. Between 1.0 and 0.75 g g(-1), axes survived cryogenic exposure but developed abnormally. The proportion of axes developing normally after being cooled in isopentane increased with increasing dehydration below 0.75 g g(-1), reaching a maximum between 0.5 and 0.25 g g(-1) after being cooled at > or =300 degrees C s(-1). Cooling rates attained in subcooled nitrogen did not exceed 250 degrees C s(-1), and normal development of axes was observed only at < or =0.4 g g(-1). These results support the hypothesis that rapid cooling enhances the feasibility of cryopreservation of desiccation-sensitive embryonic axes by increasing the upper limit of allowable water contents and overall survival.


Assuntos
Criopreservação/métodos , Sementes/química , Sementes/embriologia , Árvores/química , Árvores/embriologia , Água/análise
15.
Planta ; 213(5): 828-32, 2001 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11678289

RESUMO

Some progress has recently been made in establishing a system enabling somatic embryos to be initiated from old elite trees. We report here the first results demonstrating the molecular conformity of somatic embryos initiated from increasingly old Norway spruce (Picea abies (L.) Karst.), as indicated by an analysis of six nuclear microsatellites that showed an extremely high tendency to mutate during in vitro culture. No allelic difference was detected at these loci among plants regenerated from somatic embryos or between the former and mother plants. Moreover, phenotypical data acquired on the same 3- to 9-year-old plants growing in the field sampled for molecular analyses were totally in accord with the results on molecular conformity.


Assuntos
Picea/crescimento & desenvolvimento , Sementes/crescimento & desenvolvimento , Árvores/crescimento & desenvolvimento , Clonagem Molecular , Técnicas de Cultura , Fenótipo , Picea/embriologia , Picea/genética , Reação em Cadeia da Polimerase , Sementes/genética , Árvores/embriologia , Árvores/genética
16.
J Exp Bot ; 52(357): 761-9, 2001 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-11413212

RESUMO

To examine the possible relationship between ethylene and the capacity of embryogenic cell lines to produce mature somatic embryos of black spruce (Picea mariana (Mill.) B.S.P.), two embryogenic cell lines which exhibit different maturation capacities were used to analyse ethylene biosynthesis and that of its immediate precursor, 1-aminocyclopropane-1- carboxylic acid (ACC). Several compounds known to alter ethylene metabolism were also evaluated for their effect on the number of mature somatic embryos produced. The results showed that in the high capacity cell line, ethylene production and endogenous ACC pools were less than in the low capacity cell line. It was also demonstrated that limiting ethylene biosynthesis by adding inhibitors of ethylene biosynthesis or its physiological action to the maturation medium promoted somatic embryo production for the low capacity cell line. Conversely, lowering ethylene biosynthesis reduced the number of somatic embryos in the high capacity cell line. These results were further substantiated by the finding that the effects of amino-oxyacetic acid (AOA), an inhibitor of ethylene biosynthesis, were partially reversed by adding ethylene to both embryogenic cell lines. It is concluded that ethylene is implicated in somatic embryogenesis of black spruce and that the low capacity cell line had excess, i.e. supraoptimal, ethylene production, whereas the high capacity cell line had nearly optimal ethylene production. The relationship between ethylene and other phytohormones, and the possible effects of the interaction between ethylene and polyamines on the maturation of the somatic embryos are discussed.


Assuntos
Etilenos/metabolismo , Sementes/citologia , Árvores/embriologia , Aminoácidos Cíclicos/farmacologia , Ácido Amino-Oxiacético/farmacologia , Linhagem Celular , Etilenos/antagonistas & inibidores , Sementes/metabolismo , Nitrato de Prata/farmacologia , Árvores/metabolismo
17.
J Cell Sci ; 113 Pt 24: 4399-411, 2000 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11082033

RESUMO

In the animal life cycle, the earliest manifestations of programmed cell death (PCD) can already be seen during embryogenesis. The aim of this work was to determine if PCD is also involved in the elimination of certain cells during plant embryogenesis. We used a model system of Norway spruce somatic embryogenesis, which represents a multistep developmental pathway with two broad phases. The first phase is represented by proliferating proembryogenic masses (PEMs). The second phase encompasses development of somatic embryos, which arise from PEMs and proceed through the same sequence of stages as described for their zygotic counterparts. Here we demonstrate two successive waves of PCD, which are implicated in the transition from PEMs to somatic embryos and in correct embryonic pattern formation, respectively. The first wave of PCD is responsible for the degradation of PEMs when they give rise to somatic embryos. We show that PCD in PEM cells and embryo formation are closely interlinked processes, both stimulated upon withdrawal or partial depletion of auxins and cytokinins. The second wave of PCD eliminates terminally differentiated embryo-suspensor cells during early embryogeny. During the dismantling phase of PCD, PEM and embryo-suspensor cells exhibit progressive autolysis, resulting in the formation of a large central vacuole. Autolytic degradation of the cytoplasm is accompanied by lobing and budding-like segmentation of the nucleus. Nuclear DNA undergoes fragmentation into both large fragments of about 50 kb and multiples of approximately 180 bp. The tonoplast rupture is delayed until lysis of the cytoplasm and organelles, including the nucleus, is almost complete. The protoplasm then disappears, leaving a cellular corpse represented by only the cell wall. This pathway of cell dismantling suggests overlapping of apoptotic and autophagic types of PCD during somatic embryogenesis in Norway spruce.


Assuntos
Apoptose , Árvores , Fragmentação do DNA , DNA de Plantas , Árvores/embriologia , Árvores/genética
18.
J Exp Bot ; 51(347): 1159-62, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10948243

RESUMO

Yellow cedar seeds are dormant at maturity. The abscisic acid (ABA) content of the embryo (but not the megagametophyte) decreased approximately 2-fold following exposure of seeds to a dormancy-breaking treatment; this process was also accompanied by a 10-fold lowered sensitivity of the embryo to S:-(+)-ABA. A decline in ABA within the seed is not sufficient for dormancy breakage; reduced embryo sensitivity to ABA is also required.


Assuntos
Ácido Abscísico/fisiologia , Germinação/fisiologia , Sementes/fisiologia , Árvores/fisiologia , Ácido Abscísico/análise , Sementes/química , Árvores/embriologia
19.
J Exp Bot ; 51(343): 249-64, 2000 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-10938831

RESUMO

Several coniferous species can be propagated via somatic embryogenesis. This is a useful method for clonal propagation, but it can also be used for studying how embryo development is regulated in conifers. However, in conifers it is not known to what extent somatic and zygotic embryos develop similarly, because there has been little research on the origin and development of somatic embryos. A time-lapse tracking technique has been set up, and the development of more than 2000 single cells and few-celled aggregates isolated from embryogenic suspension cultures of Norway spruce (Picea abies L. Karst.) and embedded in thin layers of agarose has been traced. Experiments have shown that somatic embryos develop from proembryogenic masses which pass through a series of three characteristic stages distinguished by cellular organization and cell number (stages I, II and III) to transdifferentiate to somatic embryos. Microscopic inspection of different types of structures has revealed that proembryogenic masses are characterized by high interclonal variation of shape and cellular constitution. In contrast, somatic embryos are morphologically conservative structures, possessing a distinct protoderm-like cell layer as well as embryonal tube cells and suspensor. The lack of staining of the arabinogalactan protein epitope recognized by the monoclonal antibody JIM13 was shown to be an efficient marker for distinguishing proembryogenic masses from somatic embryos. The vast majority of cells in proembryogenic masses expressed this epitope and none of cells in the early somatic embryos. The conditions that promote cell proliferation (i.e. the presence of exogenous auxin and cytokinin), inhibit somatic embryo formation; instead, continuous multiplication of stage I proembryogenic masses by unequal division of embryogenic cells with dense cytoplasm is the prevailing process. Once somatic embryos have formed, their further development to mature forms requires abscisic acid and shares a common histodifferentiation pattern with zygotic embryos. Although the earliest stages of somatic embryo development comparable to proembryogeny could not be characterized, the subsequent developmental processes correspond closely to what occurs in the course of early and late zygotic embryogeny. A model for somatic embryogenesis pathways in Picea abies is presented.


Assuntos
Árvores/embriologia , Modelos Biológicos , Sementes/crescimento & desenvolvimento
20.
Planta Med ; 66(3): 294-9, 2000 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10821065

RESUMO

Five taxane diterpenoids were isolated from the seeds of the Japanese yew, Taxus cuspidata Sieb. et Zucc. The structures were established as 2 alpha,7 beta,13 alpha-triacetoxy-5 alpha-(3'-dimethylamino-3'-phenyl)-propionyloxy-2(3-->20)-aboe+ ++-taxa-9,10-dione (1) and 2 alpha,7 beta,9 alpha,10 beta-tetraacetoxy-5 alpha-[(2R,3S),N,N-dimethyl-3-phenylisoseryloxy]-taxa-4(20),11- dien-13-one (2), 2 alpha, 9 alpha, 10 beta-triacetoxy-5 alpha-cinnamoxy-taxa-4(20),11-diene-13 alpha-ol (3), taxezopidine J (4), and taxuspine D (5) on the basis of 1D, 2D NMR, and MS spectral analysis. Compounds 1, 2, and 3 are new compounds.


Assuntos
Diterpenos/isolamento & purificação , Sementes/química , Árvores/química , Diterpenos/química , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Árvores/embriologia
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