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111.
Michael M. Burrell Peter J. Mooney Margaret Blundy Dawn Carter Fiona Wilson John Green Keith S. Blundy Tom ap Rees 《Planta》1994,194(1):95-101
The aim of this work was to discover whether genetic manipulation of 6-phosphofructokinase [EC 2.7.1.11; PFK(ATP)] influenced the rate of respiration of tuber tissue of Solanum tuberosum L. Transgenic plants were produced that contained the coding sequence of the Escherichia coli pfkA gene linked to a patatin promoter. Expression of this chimaeric gene in tubers resulted in a 14to 21-fold increase in the maximum catalytic activity of PFK(ATP) without affecting the activities of the other glycolytic enzymes. Tubers, and aged disks of tuber tissue, from transformed plants showed no more than a 30% fall in the content of hexose 6-monophosphates; the other intermediates of glycolysis increased threeto eightfold. Fructose-2,6-bisphosphate was barely detectable in aged disks of transformed tubers. The relative rates of 14CO2 production from [1-14C]-and [6-14C]-glucose supplied to disks of transformed and control tubers were similar. Oxygen uptake and CO2 production by aged disks of transformed tubers did not differ significantly from those from control tubers. The same was true of CO2 production, in air, and in nitrogen, for tuber tissue. It is concluded that PFK(ATP) does not dominate the control of respiration in potato tubers.Abbreviations Fru2,6bisP
fructose-2,6-bisphosphate
- FW
freshweight
- GUS
-glucuronidase
- PFK(ATP)
6-phosphofructokinase
- PFK(PPi)
pyrophosphate: fructose-6-phosphate 1-phosphotransferase 相似文献
112.
Nambara Eiji; Keith Kallie; McCourt Peter; Naito Satoshi 《Plant & cell physiology》1994,35(3):509-513
An Arabidopsis thaliana mutant that produces green seeds thatare highly insensitive to exogenous ABA, non-dormant and severelydesiccation intolerant was isolated from a population of fastneutron-irradiated seeds. Molecular and genetic analysis ofthis mutant shows that these phenotypes are caused by an internaldeletion of approximately one third of the ABI3 gene. Thereforeabi3 mutants with the above phenotypes are representative ofnull alleles at this locus. (Received December 3, 1993; Accepted January 22, 1994) 相似文献
113.
Mark L. Carpenter Sarah A. Cassidy Keith R. Fox 《Journal of molecular recognition : JMR》1994,7(3):189-197
We have studied the interaction of the GC-specific, minor groove-binding ligand, mithramycin, with cloned DNA inserts containing isolated GC and CG sites flanked by regions of (AT)n and An · Tn using DNase I and hydroxyl radical footprinting. We find that mithramycin binds to GC better than CG and that AGCT is a better site than TGCA. Sites flanked by (AT)n appear to be bound better than those surrounded by An · Tn. Although no footprints are produced at T9GCA9 and T15CGA15, DNase I cleavage is enhanced with the GC sites suggesting that there is some interaction with the ligand. Mithramycin also alters the DNase I cleavage of (GA)n · (CT)n. 相似文献
114.
C S Keith D O Hoang B M Barrett B Feigelman M C Nelson H Thai C Baysdorfer 《Plant physiology》1993,101(1):329-332
As part of a project to identify novel maize (Zea mays L. cv B73) genes functionally, we have partially sequenced 130 randomly selected clones from a maize leaf cDNA library. Data base comparisons revealed seven previously sequenced maize cDNAs and 18 cDNAs with sequence similarity to related maize genes or to genes from other organisms. One hundred five cDNAs show little or no similarity to previously sequenced genes. Our results also establish the suitability of this library for large-scale sequencing in terms of its large insert size, proper insert orientation, and low duplication rate. 相似文献
115.
Russell B. Lingham Keith C. Silverman Gerald F. Bills Carmen Cascales Manual Sanchez Rosalind G. Jenkins Suzanne E. Gartner Isabel Martin Maria T. Diez Fernando Peláez Sagrario Mochales Yu-Lin Kong Richard W. Burg Maria S. Meinz Leeyuan Huang Mary Nallin-Omstead Scott D. Mosser Michael D. Schaber Charles A. Omer David L. Pompliano Jackson B. Gibbs Sheo B. Singh 《Applied microbiology and biotechnology》1993,40(2-3):370-374
Chaetomellic acids A and B, isolated from Chaetomella acutiseta, are specific inhibitors of farnesyl-protein transferase that do not inhibit geranylgeranyl transferase type 1 or squalene synthase. Chaetomellic acids A and B are reversible inhibitors, resemble farnesyl diphosphate and probably inhibit FPTase by substituting for farnesyl diphosphate. Chaetomellic acid production appears to be widespread within the genus Chaetomella.
Correspondence to: R. B. Lingham 相似文献
116.
Abstraction of oxygen from the HRP enhanced chemiluminescence system has no significant effect on the chemiluminescence generated. It is, therefore, proposed that in the peroxidase-luminol-perborate system at pH 7.3, chemiluminescence is generated by a direct reaction of diazaquinones with hydrogen peroxide and not, as generally assumed, from the reaction of luminol radicals with the molecular oxygen. 相似文献
117.
Abstract. We describe a model of heath vegetation, in which species were classified into five functional groups based on characteristics of their propagule pools, post-fire growth, timing and mode of reproduction and competitive status. The model assumes no recruitment without fire and a simple competitive hierarchy based on vertical stature. A critical feature of the model is an initial post-fire window of 5–6 yr in which competition from overstorey species on understorey species is reduced. Understorey functional groups differ in their ability to exploit this window. In the field, we tested five predictions derived from the model: (a) overall species richness of understorey varies inversely with overstorey density as a result of a trend in richness of woody species, but not in herbaceous species; (b) where an overstorey was present in the previous fire interval, post-fire population density is reduced in a functional group of understorey serotinous resprouting shrubs, but not in a group of understorey obligate-seeding shrubs with soil seed banks; (c) in understorey serotinous resprouting shrubs, post-fire regrowth in resprouting individuals is adversely affected by the presence of an overstorey in the preceding fire interval; (d) in understorey serotinous resprouting shrubs, levels of pre-fire propagules are lower in the presence of an overstorey, reducing the density of post-fire recruits; and (e) in understorey serotinous resprouting shrubs, recruitment relative to the pre-fire population is unaffected by overstorey species within the window of reduced competition. Of these, three tests (a,b,d) supported the model, one (e) may support the model, but the results were inconclusive and one (c) did not support the model. Limitations and further applications of the model are discussed. Our results suggest that maintenance of high densities of overstorey populations is in conflict with conservation of some understorey species. Models of the type we propose will help identify and resolve such conflicts and promote the judicious use of fire to maintain full species diversity of plant communities. 相似文献
118.
119.
Cell Cycle Arrest of Proliferating Neuronal Cells by Serum Deprivation Can Result in Either Apoptosis or Differentiation 总被引:4,自引:1,他引:3
M. Keith Howard Lindsey C. Burke Carolina Mailhos Arnold Pizzey Christopher S. Gilbert† W. Durward Lawson‡ Mary K. L. Collins§ N. Shaun B. Thomas David S. Latchman 《Journal of neurochemistry》1993,60(5):1783-1791
Abstract: Apoptotic cell death plays a critical role in the development of the nervous system. The death of mature nondividing neurons that fail to receive appropriate input from the target field has been extensively studied. However, the mechanisms mediating the extensive cell death occurring in areas of the developing brain where proliferating neuroblasts differentiate into mature nondividing neurons have not been analyzed. We show here that the cell cycle arrest of a proliferating cell of neuronal origin by removal of serum results in either apoptotic cell death or differentiation to a mature nondividing neuronal cell. The proportion of cells undergoing death or differentiation is influenced in opposite directions by treatment of the cells with cyclic AMP and retinoic acid. This suggests that following the withdrawal of signals stimulating neuroblast cell division, neuronal cells either can cease to suppress a constitutive suicide pathway and hence die by apoptosis or, alternatively, can differentiate into a mature neuronal cell. Regulation of the balance between apoptosis and neuronal differentiation could therefore play a critical role in controlling the numbers of mature neurons that form. 相似文献
120.
Pre- and Posttranslational Regulation of β-Endorphin Biosynthesis in the CNS: Effects of Chronic Naltrexone Treatment 总被引:1,自引:1,他引:0
David M. Bronstein Nicola C. Day Howard B. Gutstein Keith A. Trujillo Huda Akil 《Journal of neurochemistry》1993,60(1):40-49
Abstract: There appear to be two anatomically distinct β-endorphin (βE) pathways in the brain, the major one originating in the arcuate nucleus of the hypothalamus and a smaller one in the area of the nucleus tractus solitarius (NTS) of the caudal medulla. Previous studies have shown that these two proopiomelanocortin (POMC) systems may be differentially regulated by chronic morphine treatment, with arcuate cells down-regulated and NTS cells unaffected. In the present experiments, we examined the effects of chronic opiate antagonist treatment on βE biosynthesis across different CNS regions to assess whether the arcuate POMC system would be regulated in the opposite direction to that seen after opiate agonist treatment and to determine whether different βE-containing areas might be differentially regulated. Male adult rats were administered naltrexone (NTX) by various routes for 8 days (subcutaneous pellets, osmotic minipumps, or repeated intraperitoneal injections). Brain and spinal cord regions were assayed for total βE-ir, different molecular weight immunoreactive β-endorphin (βE-ir) peptides, and POMC mRNA. Chronic NTX treatment, regardless of the route of administration, reduced total βE-ir concentrations by 30–40% in diencephalic areas (the arcuate nucleus, the remaining hypothalamus, and the thalamus) and the midbrain, but had no effect on βE-ir in the NTS or any region of the spinal cord. At the same time, NTX pelleting increased POMC mRNA levels in the arcuate to ~ 140% of control values. These data suggest that arcuate POMC neurons are up-regulated after chronic NTX treatment (whereas NTS and spinal cord systems remain unaffected) and that they appear to be under tonic inhibition by endogenous opioids. Chromatographic analyses demonstrated that, after chronic NTX pelleting, the ratio of full length βE1–31 to more processed βE-ir peptides (i.e., βE1–27 and βE1–26) tended to increase in a dose-dependent manner in diencephalic areas. Because βE1–31 is the only POMC product that possesses opioid agonist properties, and βE1–27 has been posited to function as an endogenous anatgonist of βE1–31, the NTX-induced changes in the relative concentrations of βE1–31 and βE1–27/βE1–26 may represent a novel regulatory mechanism of POMC cells to alter the opioid signal in the synapse. 相似文献