Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 5 de 5
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Planta ; 230(2): 441-8, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19437034

RESUMO

We investigated the effects of prolonged hypoxia on the sugar uptake in tomato (Solanum lycopersicum L. var. MP-1) roots. Hydroponic cultures of whole tomato plants were submitted to hypoxic treatment for 1 week, and the roots were analyzed for sugar concentrations, hexose uptake and hexose transporter expression level. Contrary to what has been observed after anoxic shock or short-term hypoxic treatment, we show that sugar concentrations increase and hexose uptake is up-regulated in the roots after 1 week of hypoxic treatment. Increased hexose transport is concomitant with the induction of the hexose transporter gene LeHT2. These responses may be due either to a direct effect of low O(2) supply, or to a secondary effect associated with the increase in sugar concentrations, which, typically, develops in most hypoxic plants.


Assuntos
Hipóxia Celular/fisiologia , Hexoses/metabolismo , Oxigênio/metabolismo , Raízes de Plantas/metabolismo , Solanum lycopersicum/metabolismo , Transporte Biológico/fisiologia , Regulação da Expressão Gênica de Plantas , Proteínas de Transporte de Monossacarídeos/metabolismo
2.
Plant Physiol Biochem ; 45(8): 551-9, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17624795

RESUMO

A salt-sensitive genotype of Solanum lycopersicum cv. Volgogradskij was submitted to a 6-day treatment with high salt (100, 200 mM NaCl), allowed to recover for 6 days and then submitted to a second period of salt stress in order to study changes in carbohydrate metabolism related to salt adaptation. The ion, soluble sugar and starch contents, as well as sucrose biosynthetic and sugar mobilizing enzyme activities and transcript levels were determined during the salt stress/recovery/stress cycle. Sodium ions were found to accumulate preferentially in old leaves. Young leaves accumulated lower levels of sodium ions but maintained control levels of potassium ions. Hexoses accumulated to higher levels and starch was better maintained in young compared to old leaves during the two salt treatments. Sucrose accumulated dramatically only in old leaves during the initial salt treatment. Sugar accumulation was not related to decreases in the activities of sugar mobilizing enzymes, acid (EC 3.2.1.25) and neutral (EC 3.2.1.26) invertases, sucrose synthase (EC 2.4.1.13) and hexokinase (EC 2.7.1.1). The activity of the biosynthetic enzyme sucrose phosphate synthase (EC 2.3.1.14) was linked to changes in sucrose levels but not with transcript levels. These results point to the importance of post-transcriptional regulation. Transcriptional regulation could nevertheless be seen in the down-regulation of ribulose bisphosphate carboxylase small subunit (EC 4.1.1.39) in old compared to young leaves, but this was not related to sugar levels.


Assuntos
Metabolismo dos Carboidratos , Carboidratos/química , Folhas de Planta/metabolismo , Sais/farmacologia , Solanum lycopersicum/metabolismo , Íons , Solanum lycopersicum/efeitos dos fármacos , Folhas de Planta/efeitos dos fármacos , Plantas/metabolismo , Potássio/química , RNA Mensageiro/metabolismo , Ribulose-Bifosfato Carboxilase/metabolismo , Sódio/química , Cloreto de Sódio/farmacologia , Sacarose/química , Fatores de Tempo
3.
Plant Cell Environ ; 30(4): 508-17, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17324236

RESUMO

Hypoxically induced tolerance to anoxia in roots of tomato (Solanum lycopersicum) was previously shown to depend on sucrose and the induction of sucrose synthase. In contrast to maize, root hexokinase (HXK) activities did not increase during hypoxia and glucose was unable to sustain glycolytic flux under anoxia. In this paper, we asked whether hypoxic metabolism in roots would be altered in transgenic tomato plants overexpressing either a plant (Arabidopsis) or a yeast (Saccharomyces cerevisiae) HXK and whether such modifications could be related to improved energy metabolism and consequently root tolerance under anoxia. Tomato plants grown hydroponically with shoots always maintained in air were submitted to a 7 d hypoxic treatment applied by stopping air bubbling. A combination of techniques including (1)H-nuclear magnetic resonance spectroscopy, RT-PCR and enzyme analyses was used to obtain a broad picture of hypoxic root metabolism. In normoxic conditions, HXK overexpression resulted in higher ADP and AMP levels only in roots of AtHXK1 transgenic plants. During hypoxic treatment, oxygen levels in the hydroponic tank decreased rapidly to 5 kPa within the first 2 d and then remained at 5 kPa throughout the 7 d experiment. Oxygen levels were similar at 5 and 20 cm below the water surface. A decline of the adenylate energy status was observed after 2 d of hypoxic treatment, with a further decrease by 7 d in roots of non-transgenic (WT) and ScHXK2, but not in AtHXK1 transgenic plants. Sucrose synthase activity increased to comparably higher levels at 7 d of hypoxic treatment in WT and ScHXK2 compared with AtHXK1 roots. Differences between WT and the transgenic plants are discussed with respect to the metabolic response to low (hypoxia) but not zero (anoxia) oxygen.


Assuntos
Proteínas de Arabidopsis/metabolismo , Hexoquinase/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Solanum lycopersicum/genética , Nucleotídeos de Adenina/metabolismo , Proteínas de Arabidopsis/genética , Metabolismo dos Carboidratos , Hipóxia Celular , Etanol/metabolismo , Hexoquinase/genética , Solanum lycopersicum/metabolismo , Oxigênio/metabolismo , Raízes de Plantas/enzimologia , Raízes de Plantas/metabolismo , Plantas Geneticamente Modificadas/enzimologia , Plantas Geneticamente Modificadas/metabolismo , RNA Mensageiro/metabolismo , Proteínas de Saccharomyces cerevisiae/genética
4.
Exp Parasitol ; 113(4): 244-55, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16563386

RESUMO

A Trypanosoma brucei brucei DNA repeat sequence termed NlaIII repeat (NR) was originally isolated from a multidrug-resistant field isolate CP547 [Jamnadass, R., 1995. Identification and characterisation of an extrachromosomal element from a multidrug-resistant isolate of T. brucei brucei, Ph.D. thesis, Brunel University, UK]. Subsequently studied in a laboratory strain (Tb427) [Alsford, N.S., Navarro, M., Jamnadass, H.R., Dunbar, H., Ackroyd, M., Murphy, N.B., Gull, K., Ersfeld,K., 2003. The identification of circular extrachromosomal DNA in the nuclear genome of T. brucei. Molecular Microbiology 47, 277-288], NRs were exclusively episomal. Here we show that NR sequences in CP547 are present on linear chromosomes as well as on episomal circular elements. Sequence analysis shows that NRs are composed of three classes of sub-repeat arranged in a specific order. Heterogeneity in size and sequence of an episomal 6.6kbp element was shown in successive passages of the original CP547 isolate and derived clones in mice. Its copy number was unstable and was affected by selective pressure with the trypanocide diminazene aceturate. Some of the extrachromosomal elements appear to be composed of RNA-DNA hybrids. NR sequences were transcribed in a developmentally regulated manner but transcripts did not contain the spliced-leader sequence found on all trypanosome mRNAs.


Assuntos
DNA de Protozoário/química , Resistência a Múltiplos Medicamentos/genética , RNA de Protozoário/química , Sequências Repetitivas de Ácido Nucleico/genética , Trypanosoma brucei brucei/genética , Animais , Sequência de Bases , Northern Blotting , Southern Blotting , Bovinos , Cromossomos/química , Cromossomos/genética , DNA de Protozoário/genética , Desoxirribonucleases de Sítio Específico do Tipo II/metabolismo , Eletroforese em Gel de Ágar , Eletroforese em Gel de Campo Pulsado , Dados de Sequência Molecular , RNA de Protozoário/genética , RNA Líder para Processamento/química , RNA Líder para Processamento/genética , Mapeamento por Restrição , Transcrição Gênica/fisiologia , Trypanosoma brucei brucei/efeitos dos fármacos
5.
Ann Bot ; 91 Spec No: 195-204, 2003 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-12509340

RESUMO

The objective of this study was to evaluate the role of enzyme induction and aerenchyma formation in prolonged tolerance to soil flooding in a variety of underground clover (Trifolium subterraneum 'Park') previously selected for resistance. Seedlings were grown in hydroponic tanks, initially with aeration for 3 weeks and subsequently in the absence of aeration for up to 3 weeks. After 1 h in the absence of aeration, the oxygen concentration in the hydroponic medium had decreased to 1.5 %. During the 3 weeks of extreme oxygen deficiency, primary roots died and were replaced by considerable numbers of adventitious roots. Activities of many glycolytic and fermentative enzymes increased in adventitious roots. Excised adventitious roots were capable of immediate induction of ethanol in the absence of lactate production, in association with energy charge higher than that in excised roots of aerobically maintained controls. Energy charge was even higher when measured in adventitious roots in planta. Interestingly, haemoglobin protein could be correlated with energy charge. Aerenchyma was readily visualized in adventitious roots by optical microscopy of longitudinal and transverse sections. We conclude that avoidance of root anoxia via aerenchyma is the major mechanism for prolonged root tolerance in Trifolium subterraneum 'Park'.


Assuntos
Adaptação Fisiológica , Raízes de Plantas/fisiologia , Trifolium/fisiologia , Monofosfato de Adenosina/metabolismo , Endopeptidases/metabolismo , Metabolismo Energético , Indução Enzimática , Etanol/metabolismo , Fermentação , Glicólise , Lactatos/metabolismo , Oxigênio/metabolismo , Raízes de Plantas/metabolismo , Trifolium/enzimologia , Trifolium/metabolismo , Água
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA