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21.
A gene MtPPRD1, 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 emergence. Although at the protein level MtPPRD1 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 MtPPRD1 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 MtPPRD1 expression is developmentally 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, MtPPRD1 is specifically expressed in the embryo axis. Based on both experimental and in silico studies several putative roles are proposed for MtPPRD1 in Medicago truncatula, this protein can intervene (i) as an LTP in membrane 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. 相似文献
22.
Rémi Vincent Vincent Fraisier Sylvain Chaillou M. Anis Limami Eliane Deleens Belinda Phillipson Corinne Douat Jean-Pierre Boutin Bertrand Hirel 《Planta》1997,201(4):424-433
A soybean cytosolic glutamine synthetase gene (GS15) was fused with the constitutive 35S cauliflower mosaic virus (CaMV) promoter in order to direct overexpression in Lotus corniculatus L. plants. Following transformation with Agrobacterium rhizogenes, eight independent Lotus transformants were obtained which synthesized additional cytosolic glutamine synthetase (GS) in the shoots. To eliminate
any interference caused by the T-DNA from the Ri plasmid, three primary transformants were crossed with untransformed plants
and progeny devoid of TL- and TR-DNA sequences were chosen for further analyses. These plants had a 50–80% increase in total leaf GS activity. Plants were
grown under different nitrogen regimes (4 or 12 mM NH4
+) and aspects of carbon and nitrogen metabolism were examined. In roots, an increase in free amino acids and ammonium was
accompanied by a decrease in soluble carbohydrates in the transgenic plants cultivated with 12 mM NH4
+ in comparison to the wild type grown under the same conditions. Labelling experiments using 15NH4
+ were carried out in order to monitor the influx of ammonium and its subsequent incorporation into amino acids. This experiment
showed that both ammonium uptake in the roots and the subsequent translocation of amino acids to the shoots was lower in plants
overexpressing GS. It was concluded that the build up of ammonium and the increase in amino acid concentration in the roots
was the result of shoot protein degradation. Moreover, following three weeks of hydroponic culture early floral development
was observed in the transformed plants. As all these properties are characteristic of senescent plants, these findings suggest
that expression of cytosolic GS in the shoots may accelerate plant development, leading to early senescence and premature
flowering when plants are grown on an ammonium-rich medium.
Received: 17 July 1996 / Accepted: 16 October 1996 相似文献
23.
Rafiqa Améziane Céline Richard-Molard Eliane Deléens Jean-François Morot-Gaudry Anis M. Limami 《Planta》1997,202(3):303-312
In chicory, we examined how NO3
− supply affected NO3
− uptake, N partitioning between shoot and root and N accumulation in the tuberized root throughout the vegetative period.
Plants were grown at two NO3
− concentrations: 0.6 and 3 mM. We used 15N-labelling/chase experiments for the quantification of N fluxes between shoot and root and for determining whether N stored
in the tuberized root originates from N remobilized from the shoot or from recently absorbed NO3
−. The rate of 15NO3
− uptake was decreased by low NO3
− availability at all stages of growth. In young plants (10–55 days after sowing; DAS), in both NO3
− treatments the leaves were the strongest sink for 15N. In mature (tuberizing) plants, (55–115 DAS), the rate of 15NO3
− uptake increased as well as the amount of exogenous N allocated to the root. In N-limited plants, N allocation to the tuberized
root relied essentially on recent N absorption, while in N-replete plants, N remobilized from the shoot contributed more to
N-reserve accumulation in the root. In senescing plants (115–170 DAS) the rate of 15NO3
− uptake decreased mainly in N-replete plants whereas it remained almost unchanged in N-limited plants. In both NO3
− treatments the tuberized root was the strongest sink for recently absorbed N. Remobilization of previously absorbed N from
shoot to tuberized root increased greatly in N-limited plants, whereas it increased slightly in N-replete plants. As a consequence,
accumulation of the N-storage compounds vegetative storage protein (VSP) and arginine was delayed until later in the vegetative
period in N-limited plants. Our results show that although the dynamics of N storage was affected by NO3
− supply, the final content of total N, VSP and arginine in roots was almost the same in N-limited and N-replete plants. This
indicates that chicory is able to build up a store of available N-reserves, even when plants are grown on low N. We also suggest
that in tuberized roots there is a maximal capacity for N accumulation, which was reached earlier (soon after 100 DAS) in
N-replete plants. This hypothesis is supported by the fact that in N-replete plants despite NO3
− availability, N accumulation ceased and significant amounts of N were lost due to N efflux.
Received: 14 October 1996 / Accepted: 4 February 1997 相似文献
24.
Crataegus azarolus Leaves Induce Antiproliferative Activity,Cell Cycle Arrest,and Apoptosis in Human HT‐29 and HCT‐116 Colorectal Cancer Cells
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25.
Harrison Judith Brugière Norbert Phillipson Belinda Ferrario-Mery Sylvie Becker Thomas Limami Anis Hirel Bertrand 《Plant and Soil》2000,221(1):81-93
In this article we discuss the ways in which our understanding of the nature of the molecular controls of nitrogen assimilation
have been increased by the use of leguminous and non-leguminous plants with modified capacities for ammonium assimilation.
These modifications have been achieved through genetic engineering and breeding. An improved understanding of nitrogen assimilation
will be vital if improvements in crop nitrogen use efficiency are to be made to reduce the need for excessive input of fertilisers.
In this review we present an overall view of past work and more recent studies on this topic. In our work, using tobacco and
Lotus as model plants, glutamine synthetase and glutamate synthase activites have been altered by stimulating or inhibiting in
an organ- or tissue-specific manner the expression of the corresponding genes. The physiological impact of these genetic manipulations
has been studied on plants grown under different nitrogen regimes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
26.
Seed quality and carbon primary metabolism 总被引:1,自引:0,他引:1
Jean‐Baptiste Domergue Cyril Abadie Anis Limami Danielle Way Guillaume Tcherkez 《Plant, cell & environment》2019,42(10):2776-2788
Improving seed quality is amongst the most important challenges of contemporary agriculture. In fact, using plant varieties with better germination rates that are more tolerant to stress during seedling establishment may improve crop yield considerably. Therefore, intense efforts are currently being devoted to improve seed quality in many species, mostly using genomics tools. However, despite its considerable importance during seed imbibition and germination processes, primary carbon metabolism in seeds is less studied. Our knowledge of the physiology of seed respiration and energy generation and the impact of these processes on seed performance have made limited progress over the past three decades. In particular, (isotope‐assisted) metabolomics of seeds has only been assessed occasionally, and there is limited information on possible quantitative relationships between metabolic fluxes and seed quality. Here, we review the recent literature and provide an overview of potential links between metabolic efficiency, metabolic biomarkers, and seed quality and discuss implications for future research, including a climate change context. 相似文献
27.
Limami Y Pinon A Leger DY Mousseau Y Cook-Moreau J Beneytout JL Delage C Liagre B Simon A 《Biochimie》2011,93(4):749-757
Colorectal cancer is one of the most common cancer types and the third leading cause of cancer-related death in the western world. Generally, colorectal cancers are resistant to anticancer drugs. Several lines of evidence support a critical role for cyclooxygenase-2 (COX-2) during colorectal tumorigenesis and its role in chemoresistance. In this study, we focused our interest on the role played by COX-2 in apoptosis induced in HT-29 human colorectal cancer cells by ursolic acid (UA), a triterpenoid found in a large variety of plants. We showed that UA-induced apoptosis and that COX-2 was overexpressed only in apoptotic cells. We demonstrated that this overexpression was mediated by the p38 MAP kinase pathway as inhibiting its activation using a p38-specific inhibitor, SB 203580, abrogated COX-2 expression. Inhibiting COX-2 expression either by using a p38-specific inhibitor or COX-2-specific siRNA increased apoptosis. These results demonstrated that COX-2 was involved in a resistance mechanism to UA-induced apoptosis in HT-29 cells. Cells undergoing apoptosis were able to trigger a resistance mechanism by overexpressing a protein such as COX-2 to delay their death. Furthermore, we demonstrated that this resistance mechanism was independent of PGE2 production as the addition of the specific COX-2 activity inhibitor, NS-398, did not affect apoptosis in UA-treated cells. 相似文献
28.
Pinon A Limami Y Micallef L Cook-Moreau J Liagre B Delage C Duval RE Simon A 《Experimental cell research》2011,(12):1669-1676
Melanoma is one of the most aggressive forms of cancer with a continuously growing incidence worldwide and is usually resistant to chemotherapy agents, which is due in part to a strong resistance to apoptosis. The resistance mechanisms are complex and melanoma cells may have diverse possibilities for regulating apoptosis to generate apoptotic deficiencies. In this study, we investigated the relationship between melanogenesis and resistance to apoptosis induced by ursolic acid, a natural chemopreventive agent, in B16-F0 melanoma cells. We demonstrated that cells undergoing apoptosis are able to delay their own death. It appeared that tyrosinase and TRP-1 up-regulation in apoptotic cells and the subsequent production of melanin were clearly implicated in an apoptosis resistance mechanism; while TRP-2, a well known mediator of melanoma resistance to cell death, was repressed. Our results confirm the difficulty of treating melanomas, since, even undergoing apoptosis, cells are nevertheless able to trigger a resistance mechanism to delay death. 相似文献
29.
Morère-Le Paven MC Viau L Hamon A Vandecasteele C Pellizzaro A Bourdin C Laffont C Lapied B Lepetit M Frugier F Legros C Limami AM 《Journal of experimental botany》2011,62(15):5595-5605
Primary root growth in the absence or presence of exogenous NO(3)(-) was studied by a quantitative genetic approach in a recombinant inbred line (RIL) population of Medicago truncatula. A quantitative trait locus (QTL) on chromosome 5 appeared to be particularly relevant because it was seen in both N-free medium (LOD score 5.7; R(2)=13.7) and medium supplied with NO(3)(-) (LOD score, 9.5; R(2)=21.1) which indicates that it would be independent of the general nutritional status. Due to its localization exactly at the peak of this QTL, the putative NRT1-NO(3)(-) transporter (Medtr5g093170.1), closely related to Arabidopsis AtNRT1.3, a putative low-affinity nitrate transporter, appeared to be a significant candidate involved in the control of primary root growth and NO(3)(-) sensing. Functional characterization in Xenopus oocytes using both electrophysiological and (15)NO(3)(-) uptake approaches showed that Medtr5g093170.1, named MtNRT1.3, encodes a dual-affinity NO(3)(-) transporter similar to the AtNRT1.1 'transceptor' in Arabidopsis. MtNRT1.3 expression is developmentally regulated in roots, with increasing expression after completion of germination in N-free medium. In contrast to members of the NRT1 superfamily characterized so far, MtNRT1.3 is environmentally up-regulated by the absence of NO(3)(-) and down-regulated by the addition of the ion to the roots. Split-root experiments showed that the increased expression stimulated by the absence of NO(3)(-) was not the result of a systemic signalling of plant N status. The results suggest that MtNRT1.3 is involved in the response to N limitation, which increases the ability of the plant to acquire NO(3)(-) under N-limiting conditions. 相似文献
30.
Elisabeth Planchet Olivier Rannou Claudie Ricoult Anis M Limami 《Plant signaling & behavior》2011,6(7):1074-1076
Effects of water deficit and/or abscisic acid (ABA) were investigated on early seedling growth of Medicago truncatula, and on glutamate metabolism under dark conditions. Water deficit (simulated by polyethylene glycol, PEG), ABA and their combination resulted in a reduction in growth rate of the embryo axis, and also in a synergistic increase of free amino acid (AA) content. However, the inhibition of water uptake retention induced by water deficit seemed to occur in an ABA-independent manner. Expression of several genes involved in glutamate metabolism was induced during water deficit, whereas ABA, in combination or not with PEG, repressed them. The only exception came from a gene encoding 1-pyrroline-5-carboxylate synthetase (P5CS) which appeared to be induced in an ABA-dependent manner under water deficit. Our results demonstrate clearly the involvement of an ABA-dependent and an ABA-independent regulatory system, governing growth and glutamate metabolism under water deficit.Key words: abscisic acid, amino acid metabolism, water deficit, glutamate, Medicago truncatula, seedlingsTo counter the effects of unfavorable environmental conditions, young seedlings and plants have developed complex cellular signaling mechanisms which require distinct physiological and metabolic adjustments, such as sugar, amino acid or amine accumulation1 through different pathways. The phytohormone abscisic acid (ABA) has been reported to be rapidly produced and accumulated under different environmental stresses, and responses mediated by this hormone lead to the induction of complex tolerance mechanisms to osmotic stress.2 However, it has been shown that the drought-inducible genes were governed by both ABA-dependent and ABA-independent regulatory systems,3 but it is not entirely clear how water deficit and exogenous ABA could affect and regulate plant nitrogen metabolism when applied simultaneously. 相似文献