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191.
Alteration of tobacco floral organ identity by expression of combinations of Antirrhinum MADS-box genes 总被引:4,自引:3,他引:1
Brendan Davies Alexandra Di Rosa Tinka Eneva Heinz Saedler Hans Sommer 《The Plant journal : for cell and molecular biology》1996,10(4):663-677
Floral organ identity is largely controlled by the spatially restricted expression of several MADS-box genes. In Antirrhinum majus these organ identity genes include DEF, GLO and PLE . Single and double mutant analyses indicated that the type of organ found in a particular whorl is dependent on which combination of these genes is expressed there. This paper reports the ectopic expression of Antirrhinum organ identity genes, alone and in combinations, in transgenic tobacco. Although the phenotypes are broadly in agreement with the genetic predictions, several unexpected features are observed which provide information concerning the action of the organ identity genes. The presumed tobacco homologue of DEF, NTDEF , has been isolated and used to investigate the influence of ectopic expression of the Antirrhinum organ identity genes on the endogenous tobacco genes. Analysis of the spatial and temporal expression patterns of NTDEF and NTGLO reveals that the boundaries are not coincident and that differences exist in the regulatory mechanisms of the two genes concerning both induction and maintenance of gene expression. Evidence is provided which indicates that organ development is sensitive to the relative levels of organ identity gene expression. Expression of the organ identity genes outside the flower or inflorescence produced no effects, suggesting that additional factors are required to mediate their activity. These results demonstrate that heterologous genes can be used to predictably influence floral organ identity but also reveal the existence of unsuspected control mechanisms. 相似文献
192.
A simple technic is described to produce well spread gymnosperm chromosomes. Root tip meristems are digested with a pectinase:cellulase mixture to produce a cell suspension which then is squashed to yield flat, well spread chromosome complements that can be stained or used for in situ hybridization. 相似文献
193.
194.
Cloning of a coconut endosperm cDNA encoding a 1-acyl-sn-glycerol-3-phosphate acyltransferase that accepts medium-chain-length substrates. 总被引:6,自引:1,他引:5
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D S Knutzon K D Lardizabal J S Nelsen J L Bleibaum H M Davies J G Metz 《Plant physiology》1995,109(3):999-1006
Immature coconut (Cocos nucifera) endosperm contains a 1-acyl-sn-glycerol-3-phosphate acyltransferase (LPAAT) activity that shows a preference for medium-chain-length fatty acyl-coenzyme A substrates (H.M. Davies, D.J. Hawkins, J.S. Nelsen [1995] Phytochemistry 39:989-996). Beginning with solubilized membrane preparations, we have used chromatographic separations to identify a polypeptide with an apparent molecular mass of 29 kD, whose presence in various column fractions correlates with the acyltransferase activity detected in those same fractions. Amino acid sequence data obtained from several peptides generated from this protein were used to isolate a full-length clone from a coconut endosperm cDNA library. Clone pCGN5503 contains a 1325-bp cDNA insert with an open reading frame encoding a 308-amino acid protein with a calculated molecular mass of 34.8 kD. Comparison of the deduced amino acid sequence of pCGN5503 to sequences in the data banks revealed significant homology to other putative LPAAT sequences. Expression of the coconut cDNA in Escherichia coli conferred upon those cells a novel LPAAT activity whose substrate activity profile matched that of the coconut enzyme. 相似文献
195.
The nucleotide sequence of a cDNA prepared from poly(A)+ RNA from Lycopersicon esculentum fruit codes for a protein, M
r 20812, with features representative of the protein core of arabinogalactan proteins. The deduced amino acid sequence resembles that of peptides of arabinogalactan proteins isolated from carrot and rose and is most similar to the sequence of tryptic peptides from Lolium multiflorum (Gleeson et al., Biochem J 264 (1989) 857–862). The similar sequences include a number of Ala-Pro repeats, a feature considered distinctive of arabinogalactan proteins. The amino acid composition is similar to that of the peptide core of the Lolium multiflorum arabinogalactan protein; alanine, serine and proline account for 57% of the polypeptide. The mRNA corresponding to the cDNA sequence was detected in roots, leaves and fruit. The levels of mRNA are reduced in older leaves, in fruit that have commenced ripening and in leaves and fruit that have been wounded. 相似文献
196.
Rapid changes in oxidative metabolism as a consequence of elicitor treatment of suspension-cultured cells of French bean (Phaseolus vulgaris L.) 总被引:1,自引:0,他引:1
Duncan Robertson Dewi R. Davies Chris Gerrish Steven C. Jupe G. Paul Bolwell 《Plant molecular biology》1995,27(1):59-67
Stressed plant cells often show increased oxygen uptake which can manifest itself in the transient production of active oxygen species, the oxidative burst. There is a lack of information on the redox status of cells during the early stages of biotic stress. In this paper we measure oxygen uptake and the levels of redox intermediates NAD/NADH and ATP and show the transient induction of the marker enzyme for redox stress, alcohol dehydrogenase. Rapid changes in the redox potential of elicitor-treated suspension cultures of French bean cells indicate that, paradoxically, during the period of maximum oxygen uptake the levels of ATP and the NADH/NAD ratio fall in a way that indicates the occurrence of stress in oxidative metabolism. This period coincides with the maximum production of active oxygen species particularly H2O2. The cells recover and start producing ATP immediately upon the cessation of H2O2 production. This indicates that the increased O2 uptake is primarily incorporated into active O2 species. A second consequence of these changes is probably a transient compromising of the respiratory status of the cells as indicated in expression of alcohol dehydrogenase. Elicitor-induced bean ADH was purified to homogeneity and the Mr 40 000 polypeptide was subjected to amino acid sequencing. 15% of the whole protein was sequenced from three peptides and was found to have nearly 100% sequence similarity to the amino acid sequence for pea ADH1 (PSADH1). The cDNA coding for the pea enzyme was used to demonstrate the transient induction of ADH mRNA in elicitor-treated bean cells. Enzyme activity levels also increased transiently subsequently. Increased oxygen uptake has previously been thought to be associated with provision of energy for the changes in biosynthesis that occur rapidly after perception of the stress signal. However the present work shows that this rapid increase in oxygen uptake as a consequence of elicitor action is not wholly associated with respiration. 相似文献
197.
198.
Macroscopic instantaneous and time-dependent currents have been measured in the vacuolar membrane of Beta vulgaris using a patch clamp configuration analogous to whole cell mode. At low cytosolic Ca2+ and in the absence of Mg2+, only an instantaneous current was observed. This current is carried predominantly by cations (PKPCl 71, pnapcl 41 and arginine is also conducted). The instantaneous current can be activated by ATP4– (e.g., ATP-activated mean K+ current density was –20 mA.m–2 at a membrane voltage of –20 mV) and by increasing cytosolic pH and Mg2+ (raising Mg2+ from 0 to 0.4 mm induced a mean current density increase of –7 mA.m–2 at –20 mV). Such current can be activated by simultaneous addition of putative in vivo concentrations of ATP4–/MgATP/Mg
free
2+
(in the presence of bafilomycin to inhibit the vacuolar ATPase) and further modulated by cytosolic pH. With vacuolar K+ concentration greater than that of the cytosol, activation of the instantaneous current would mediate vacuolar K+ release over the range of physiological membrane voltage. It is argued that the ATP4–-activated current, in addition to acting as a K+ mobilization pathway, could provide a counter-ion (shunt) conductance, allowing the two electrogenic H+ pumps which reside in the vacuolar membrane to acidify the vacuolar lumen.A separate time-dependent current, which was not observed at low Ca2+ concentrations (less than 500 nm) could also be elicited by addition of Mg2+ at the cytoplasmic membrane face. This current was stimulated by increasing cytoplasmic pH.The authors are grateful to the BBSRC for financial support (Grant PG87/529) and to the Royal Society (University Research Fellowship to J.M.D.). We thank C. Abbott, K. Partridge and J. Robinson for plant cultivation; A. Amtmann, A. Bertl, D. Gradmann and G. Thiel for helpful discussion. 相似文献
199.
Susan J. Holt Peter Alexander Chris B. Inman Donna E. Davies 《Experimental cell research》1995,217(2)
Ligand-induced translocation of epidermal growth factor receptors (EGF-R) to the nucleus of NR6/HER fibroblasts has been studied by immunoelectron microscopy. Following treatment of NR6/HER cells with epidermal growth factor (EGF) for 1 h, there was a decrease in EGF-R labeling at the plasma membrane and a corresponding increase in EGF-R in the nucleus. This was preceded by a rapid and sustained increase in nuclear phosphotyrosine content, detectable within 2 min of EGF treatment. EGF-R translocation into the nucleus was completely prevented by 18 h serum starvation prior to treatment with EGF. These results indicate that translocation of EGF-R to the nucleus is a controlled process and they suggest theft EGF-R may directly influence nuclear function. 相似文献
200.
J. Davies 《Genetics》1995,139(4):1465-1468