Phylogenetic relationships of the chloroplast genomes in the genus Glycine inferred from four intergenic spacer sequences

The nucleotide sequences of four intergenic spacer regions of chloroplast DNA, atpB-rbcL, trnS-trnG, rps11-rpl36, and rps3-rpl16, were analyzed in the genus Glycine. Phylogenetic analysis based on the sequence data using Neonotonia wightii as the outgroup generated trees supporting the classification of two subgenera, Soja and Glycine, and three plastome groups in the subgenus Glycine. The results were consistent with the presence of diversified chloroplast genomes within tetraploid plants of G. tabacina and G. tomentella, as well as with a close relationship between G. tomentella and G. dolichocarpa that had been suggested based on morphological analyses. Little sequence variation was found in the subgenus Soja, suggesting that G. soja rapidly expanded its distribution in East Asia. The analysis also showed that the differentiation into three plastome groups in the subgenus Glycine occurred in the early stages of its evolution, after the two subgenera diverged.     

Reaction mechanism of (Ca2+, Mg2+)-ATPase of sarcoplasmic reticulum. The role of Mg2+ that activates hydrolysis of the phosphoenzyme

The role of Mg2+ in the activation of phosphoenzyme hydrolysis has been investigated with the (Ca2+, Mg2+)-ATPase of sarcoplasmic reticulum vesicles. The enzyme of the native and solubilized vesicles was phosphorylated with ATP at 0 degrees C, pH 7.0, in the presence of Ca2+ and Mg2+. When Ca2+ and Mg2+ in the medium were chelated, phosphoenzyme hydrolysis continued for about 15 s and then ceased. The extent of this hydrolysis increased with increasing concentrations of Mg2+ added before the start of phosphorylation. This shows that the hydrolysis was activated by the Mg2+ added. The Mg2+ which activated phosphoenzyme hydrolysis was distinct from Mg2+ derived from MgATP bound to the substrate site. The Mg2+ site at which Mg2+ combined to activate phosphoenzyme hydrolysis was located on the outer surface of the vesicular membranes. During the catalytic cycle, Mg2+ combined with the Mg2+ site before Ca2+ dissociated from the Ca2+ transport site of the ADP-sensitive phosphoenzyme with bound Ca2+. This Mg2+ did not activate hydrolysis of the ADP-sensitive phosphoenzyme with bound Ca2+, but markedly activated hydrolysis of the ADP-insensitive phosphoenzyme without bound Ca2+. It is concluded that during the catalytic cycle, Mg2+ activates phosphoenzyme hydrolysis only after Ca2+ has dissociated from the Ca2+ transport site of phosphoenzyme.     

Adiponectin and AMP kinase activator stimulate proliferation,differentiation, and mineralization of osteoblastic MC3T3-E1 cells

Background  

Adiponectin is a key mediator of the metabolic syndrome that is caused by visceral fat accumulation. Adiponectin and its receptors are known to be expressed in osteoblasts, but their actions with regard to bone metabolism are still unclear. In this study, we investigated the effects of adiponectin on the proliferation, differentiation, and mineralization of osteoblastic MC3T3-E1 cells.     

Chicken ornithine transacarbamylase: Its unexpected expression

Ornithine transcarbamylase (OTC), one of the enzymes of the urea cycle, is detectable in some strains of chickens, although they have no functional urea cycle. The enzyme consists of three identical subunits of 36 kd and is present in mitochondria of the kidney. Using immunoabsorbent column chromatography, we found further evidence that the enzyme is detectable as a precursor form (40 kd) in chicken brain, heart, liver, pancreas, gizzard, small intestine, and breast muscle. When an extract of small intestine containing only precursor OTC was treated with a kidney extract, the precursor was converted into OTC. This suggests that there is a tissue-specific processing protease in the kidney which splits a peptide off the precursor, causing the expression of OTC activity in this organ. However, the reason why the enzyme or its precursor is expressed in these organs is not known. The results of this study suggest that, unlike mammals, chickens are more organ specific with regard to the ability to incorporate precursor OTC into mitochondria.     

THE INCORPORATION OF LABELLED ACETATE INTO CEREBROSIDE AND OTHER LIPIDS OF THE DEVELOPING MOUSE BRAIN

—Cerebroside in the brain is highly localized in myelin and has a relatively slow turnover rate. The aim of this study was to evaluate the true cerebroside biosynthetic activity under conditions in which the degradation and reutilization of brain lipids were as small as possible. The 3-week-old mice were decapitated at 0·5, 1, 2·5, 5 and 15 min after the intraperitoneal injection of labelled acetate and the incorporation of radioactivity into each lipid class was examined. Even at 0·5 min, a considerable amount of radioactivity was found in simple lipids, especially in the free fatty acid fraction, and in the course of time the radioactivity of complex lipids increased. On the other hand, the incorporation of radioactivity into cerebrosides was extremely small throughout the experimental period. Results indicated that the low radioactivity of cerebroside might be due to its high content of long-chain fatty acids which were weakly labelled. The radioactivity of the sphingosine moiety was also low. In short, one of the rate-limiting steps of cerebroside synthesis in brain might exist in long-chain fatty acid and sphingosine synthesis. In addition, the incorporation curves of each component of cerebroside were compared with each other and the difference of the incorporation pattern of non-hydroxy fatty acids of cerebroside was noted.     

Introduction of Foreign Genes into Tomato Protoplasts by Electroporation

The conditions required for the electroporation of a plasmidwhich harbored the gene for chloramphenicol acetyltransferase(CAT) into protoplasts from cultivated tomato leaves were optimizedat 666 or 7,000 V/cm (single discharge) using a 47-µFcapacitor in the presence of 10-100 µg DNA. The CAT genewas strongly expressed by when under the control of the promoterfor the 35S RNA from cauliflower mosaic virus and CAT activitywas detected in cells 10 days after electroporation. (Received July 28, 1988; Accepted March 23, 1989)     

Inhibition by A23187 of conformational changes involved in the Ca(2+)-induced activation of sarcoplasmic reticulum Ca(2+)-ATPase.

We previously showed that A23187 in high ionophore/protein ratios almost completely inhibits the sarcoplasmic reticulum Ca(2+)-ATPase [Hara, H. & Kanazawa, T. (1986) J. Biol. Chem. 261, 16584-16590]. In an attempt to obtain information on the mechanism of this inhibition, the effects of A23187 on conformational changes involved in the Ca(2+)-induced activation of the enzyme were investigated. The purified enzyme from sarcoplasmic reticulum of rabbit skeletal muscle as well as the purified enzyme labeled with fluorescein 5-isothiocyanate (FITC) were preincubated with A23187 in the absence of Ca2+ at pH 7.0 and 0 degrees C for 45 min. The activation of the enzyme following addition of CaCl2 was assessed by determining the capacity for rapid formation of phosphoenzyme from ATP. This activation was strongly inhibited by the preincubation with A23187. This indicates that the previously observed inhibition of the Ca(2+)-ATPase is mostly due to hindrance of the Ca(2+)-induced activation of the enzyme. In the control, in which the FITC-labeled enzyme was preincubated without A23187, the fluorescence intensity of the bound FITC decreased in a biphasic manner upon addition of CaCl2. The first rapid phase of this fluorescence drop was unaffected by A23187, whereas its second slow phase was almost completely inhibited by this drug. These results show that the Ca(2+)-dependent conformational change is biphasic and that the second slow phase (but not the first rapid phase) of this conformational change is inhibited by A23187. This suggests that the observed inhibition of Ca2+ activation is attributed to hindrance of the second slow phase of the Ca(2+)-dependent conformational change.     

Structure and dynamics of natural populations of polyploid trilliums

To confirm predominant self-pollination in natural populations ofTrillium apetalon (2n=4x=20, SSUU), chromosome constitutions of endosperms (2n=30, SSSUUU) fertilized in nature were analyzed for the patterns of H-segments of cold-treated chromosomes. The endosperms were of two kinds: homo-constitutions in which three chromosomes in each of the ten sets of homologues were of the same patterns of H-segments and hetero-constitutions in which one chromosome in a set of three homologous chromosomes was different from the other two. Out of 30 endosperms, 27 (90%) were of homo-constitutions and only three (10%) were of hetero-constitutions. Since the population consisted of various homokaryotypes in which each of the ten pairs of homologous chromosomes was homozygous for the patterns of H-segments, the endosperms of homo-constitutions were the result of self-pollination, and those of hetero-constitutions were from cross-pollination. Due to pollination tests conducted in two natural populations, many good seeds were found in the fruits from both open-pollinated flowers and those covered with cotton-bags. In striking contrast, no good seeds were found in the fruits from flowers castrated and pollinated in the open-air. An additional evidence of predominant self-pollination and occasional cross-pollination was given by analyzing spatial distribution of plants of various karyotypes in a population.