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91.
Contribution of sucrose synthase, ADP-glucose pyrophosphorylase and starch synthase to starch synthesis in developing pea seeds 总被引:11,自引:0,他引:11
Using genetic variability existing amongst nine pea genotypes (Pisum sativum L.), the biochemical basis of sink strength in developing pea seeds was investigated. Sink strength was considered to be reflected by the rate of starch synthesis (RSS) in the embryo, and sink activity in the seed was reflected by the relative rate of starch synthesis (RRSS). These rates were compared to the activities of three enzymes of the starch biosynthetic pathway [sucrose synthase (Sus), ADP-glucose pyrophosphorylase and starch synthase] at three developmental stages during seed filling (25, 50 and 75% of the dry seed weight). Complete sets of data collected during seed filling for the nine genotypes showed that, for all enzyme activities (expressed on a protein basis), only Sus in the embryo and seed coat was linearly and significantly correlated to RRSS. The contribution of the three enzyme activities to the variability in RSS and RRSS was evaluated by multiple regression analysis for the first two developmental stages. Only Sus activity in the embryo could explain, at least in part, the significant variability observed for both the RSS and the RRSS at each developmental stage. We conclude that Sus activity is a reliable marker of sink activity in developing pea seeds. 相似文献
92.
Sea urchin Hox genes: insights into the ancestral Hox cluster 总被引:3,自引:0,他引:3
We describe the Hox cluster in the radially symmetric sea urchin and
compare our findings to what is known from clusters in bilaterally
symmetric animals. Several Hox genes from the direct-developing sea urchin
Heliocidaris erythrogramma are described. CHEF gel analysis shows that the
Hox genes are clustered on a < or = 300 kilobase (kb) fragment of DNA,
and only a single cluster is present, as in lower chordates and other
nonvertebrate metazoans. Phylogenetic analyses of sea urchin, amphioxus,
Drosophila, and selected vertebrate Hox genes confirm that the H.
erythrogramma genes, and others previously cloned from other sea urchins,
belong to anterior, central, and posterior groups. Despite their radial
body plan and lack of cephalization, echinoderms retain at least one of the
anterior group Hox genes, an orthologue of Hox3. The structure of the
echinoderm Hox cluster suggests that the ancestral deuterostome had a Hox
cluster more similar to the current chordate cluster than was expected Sea
urchins have at least three Abd-B type genes, suggesting that Abd-B
expansion began before the radiation of deuterostomes.
相似文献
93.
94.
Rates of net photosynthesis and dark respiration were determined under submersed and emerged conditions for Hesperophycus harveyanus S. & G. and Pelvetia fastigiata f. gracilis (Decne.) S. & G. Both species exhibited submersed photosynthesis-light relationships and dark respiration rates similar to those established for other closely related intertidal, fucoids. Maximal net photosynthesis of H. harveyanus (0.21 mmol O2 g dry wt.-1· h-1; 0.18 mmol CO2 g dry wt.-1· h-1) was similar to that of P. fastigiata f. gracilis (0.17 mmol. O2 g dry wt.-1· h-1; 0.14 mmol CO2 g dry wt. -1· h-1). Light saturation occurred between 150 and 250 μE · m-2· s-1 for H. harveyanus and between 75 and 150 μE · m-2· s-1 for P. fastigiata f. gracilis; photon flux densities required for compensation were 6.4 and 9.2 μE · m-2· s-1, respectively. Photoinhibition was not observed for either species. The light-saturated, submersed net photosynthetic performances of both species varied significantly with temperature. Greatest photosynthetic rates were obtained at 23° C for H. harveyanus and at 18° C for P. fastigiata f. gracilis. Under emersed conditions, the maximal net photosynthetic rate and the photon flux densities required for saturation were greater for H. harveyanus (0.08 mmol CO2 g dry wt.-1· h-1; 260 to 700 μE · m-2· s-1) than for P. fastigiata f. gracilis (0.02 mmol CO2g dry wt.-1· h-1; 72 to 125 μE · m-2· s-1). However, for both species, emersed photosynthetic rates were much lower (14–44%) than those obtained under submersed conditions. Desiccation negatively influenced emersed photosynthesis, of both species, but H. harveyanus thalli contained more water when fully hydrated and lost water more slowly during dehydration, thus suggesting greater photosynthetic potential during field conditions of emersion. 相似文献
95.
P Policastro M Phillips E Oates E Herbert J L Roberts N Seidah M Chrétien 《European journal of biochemistry》1981,116(2):255-259
The precursor to corticotropin and beta-endorphin was synthesized in a reticulocyte cell-free system under the direction of mRNA from mouse AtT-20 pituitary tumor cells in the presence of [3H]proline, [3H]phenylalanine, [3H]leucine, [3H]valine, [3H]isoleucine or [35S]methionine. Automatic Edman degradation of the radioactive cell-free product showed the following N-terminal sequence: Pro-1, Met-2, Leu-11, Leu-12, Leu-13, Leu-15, Leu-16, Leu-17, Ile-21 and Val-23. The corticotropin-endorphin precursor was also labeled in AtT-20 cells with [3H]valine, [3H]leucine, [3H]tryptophan, [3H]serine, [35S]methionine or [35S]cysteine. Automatic Edman degradation of the radioactive intact cell form gave the following N-terminal sequence: Trp-1, Cys-2, Leu-3, Ser-5, Ser-6, Val-7, Cys-8, Leu-11, Leu-17, Leu-18 and tentatively Met-27. The sequence of the intact cell form from AtT-20 cells matches the sequence of the cell-free form of bovine pituitary precursor beginning at Trp-27, as determined by recombinant DNA technology [Nakanishi, S., Inoue, A., Kita, T., Nakamura, M., Chang, A. C. Y., Cohen, S. N., and Numa, S. (1979) Nature (Lond.) 278, 423-427]. The sequence of the mouse pituitary mRNA-directed cell-free translation product also matches the bovine precursor beginning at Pro-2. The results suggest that both the mouse and bovine precursors possess a signal sequence of 26 amino acids which is cleaved in intact cells. CNBr cleavage of [35S]cysteine-labelled intact cell precursor gave rise to an N-terminal fragment of a size compatible with the presence of a methionyl residue at or near position 27. 相似文献
96.
Substitution of 15-hydroxyeicosatetraenoic acid in the phosphoinositide signaling pathway 总被引:6,自引:0,他引:6
A B Legrand J A Lawson B O Meyrick I A Blair J A Oates 《The Journal of biological chemistry》1991,266(12):7570-7577
Consideration of how 15-hydroxyeicosatetraenoic acid (15-HETE) might exert its biological actions led us to investigate the consequences of its incorporation into bovine pulmonary arterial endothelial cell (BPAEC) phospholipids [3H]15(S)-HETE was incorporated mainly (89%) into phosphatidylinositols, predominantly as 1-stearoyl-2-(15-HETE) phosphatidylinositol. By contrast 5(S)- and 12(S)-HETE are incorporated largely into phosphatidylcholine. 15-HETE had a long persistence in the phosphatidylinositols of BPAEC with a half-life of 12 h; its uptake was concentration-dependent, and it accumulated so that 2-(15-HETE) phosphatidylinositol accounted for 10.9% of total phosphatidylinositol after four sequential 1-h incubations of cells with 1 microM 15(S)-HETE. After incubating BPAEC with 15(S)-HETE, stimulation of the cells with bradykinin led to an increase in the levels of 15-HETE. Following addition of bradykinin to cells exposed to [3H]15(S)-HETE, a radiolabeled diacylglycerol was isolated. A mass spectrum of its pentafluorobenzoyl (PFBO) trimethylsilyl (Me3Si) derivative obtained with direct electron capture negative ion chemical ionization mass spectrometry (DNICI/MS) revealed a molecular anion and fragment ions that were identical with those observed with the PFBO/Me3Si derivative of authentic 1-stearoyl-2-(15-HETE) diacylglycerol. There was a lesser quantity of 1-oleoyl-2-(15-HETE) diacylglycerol. An increase in the quantity of 1-stearoyl-2-(15-HETE) diacylglycerol from 6 +/- 1.4 pmol/10(7) cells in the basal state to 12.7 +/- 3.5 after bradykinin was measured by DNICI/MS utilizing a deuterium-labeled analog as an internal standard. Thus, incorporation of 15(S)-HETE into the phosphatidylinositol of these cells led to the release of altered second messengers. 相似文献
97.
John F. Oates 《International journal of primatology》1984,5(1):51-61
Some new field observations on West African pottos are presented and compared with previously published information on substrate
use and diet. This evidence suggests that the predominant means by which pottos find food is by carefully searching branches
in the forest canopy with their noses and that gums and slow-moving invertebrates found on branch surfaces are major components
of their diet. When fruits are scarce, gums may be the potto’s chief source of energy. It is argued that the potto’s deliberate
locomotion and some of its anatomical peculiarities are related primarily to this diet and foraging behavior, rather than
to concealment from predators or the capture of birds, two factors previously suggested to have been important in the evolution
of the potto’s locomotor technique. The potto’s niche is compared to that of other lorisid primates and is found to resemble
closely that of Galago crassicaudatusin several respects. 相似文献
98.
John F. Oates 《International journal of primatology》1988,9(5):457-478
Observations of the feeding behavior of wild olive colobus monkeys (Procolobus verus)were made in southern Sierra Leone, West Africa. Most data came from systematically sampling one habituated social group,
which inhabited old secondary rain forest on Tiwai Island. Olive colobus at Tiwai were highly selective feeders, obtaining
most of their food from a small number of uncommon middle-canopy trees, from the forest understory, and from climbers. Mature
leaf blades were largely ignored; young foliage (particularly of climbers) was a year-round dietary staple, while seeds, flowers,
and mature leaf petioles were seasonally important. It is argued that this diet results largely from selection for two different
attributes of food: high digestibility and physical location. Preferred foods had low fiber and tannin contents, while preferred
feeding sites were in thick low growth and climber tangles. P. verusis the smallest extant primate species using a foregut fermentation system. Observations of its diet accord with inferences
drawn from dental anatomy, digestive physiology, and considerations of body size. 相似文献
99.
100.