Two new iridoid glucosides from Ixora chinensis

From leaves and twigs of Ixora chinensis, two new iridoid glucosides, ixoroside (1) and ixoside (7,8-dehydroforsythide) (2) along with known geniposidic acid (3) have been isolated and their structures have been established.     

Procedure for the efficient acquisition of progeny seeds from crossed potato plants grafted onto tomato

Potato, Solanum tuberosum L. is an important crop. However, it is difficult to breed potato cultivars by applying conventional crossing methods because potato has a tetraploid genome and is vegetatively propagated. Flower formation and tuber development occur simultaneously. Many potato cultivars hardly produce any fruits after crossing and fail to produce seeds. We report an improved procedure for obtaining progeny seeds by grafting potatoes onto tomatoes. The rate of fruit formation was more than 19% when the grafted potatoes were used for the crossing experiments, whereas crossing using the ungrafted plants showed a rate of 1.1%. This result suggests that our procedure results in the easy acquisition of null-segregant progenies by crossing mutant lines. It is also expected to improve conventional potato breeding.     

Solaniol, a Toxic Metabolite of Fusarium solani

Fusarium solani M-1-1 isolated from moldy bean hulls produces T-2 toxin, diacetoxyscirpenol, and a new toxic trichothecene, solaniol, in Czapek-Dox-peptone medium.     

Cooperative conformational change and aggregation of concanavalin A in alkaline solutions

Three properties, the binding activity to Sephadex G-75, conformation, and the extent of aggregation, of concanvalin A. (con A) in alkaline pH solutions were examined with special attention to the time course and their time-independent final values. Highly cooperative conformational changes among four subunits were suggested which were coupled either with protonation in the case of demetallized con A or with metal binding in the case of metal-liganded con A. Midpoints of the conversions of the metal-liganded con A were about pH 8.8, 9.1 and 9.1 with respect to the activity, the conformational change and the aggregation, respectively. These values were about 1 pH higher than the corresponding values of demetallized con A: 7.9, 8.05 and 8.2. Each conversion took place in narrow pH ranges. The pH range for the loss of activity was found to be significantly lower than those of the other two. The aggregation was suggested not to be coupled with the conformational change. Dissociation into subunits did not take place indicating strong interactions among four subunits in the tetramer.     

Production of a Doubly Chiral Compound, (4R,6R)-4-Hydroxy-2,2,6-Trimethylcyclohexanone, by Two-Step Enzymatic Asymmetric Reduction

A practical enzymatic synthesis of a doubly chiral key compound, (4R,6R)-4-hydroxy-2,2,6-trimethylcyclohexanone, starting from the readily available 2,6,6-trimethyl-2-cyclohexen-1,4-dione is described. Chirality is first introduced at the C-6 position by a stereoselective enzymatic hydrogenation of the double bond using old yellow enzyme 2 of Saccharomyces cerevisiae, expressed in Escherichia coli, as a biocatalyst. Thereafter, the carbonyl group at the C-4 position is reduced selectively and stereospecifically by levodione reductase of Corynebacterium aquaticum M-13, expressed in E. coli, to the corresponding alcohol. Commercially available glucose dehydrogenase was also used for cofactor regeneration in both steps. Using this two-step enzymatic asymmetric reduction system, 9.5 mg of (4R,6R)-4-hydroxy-2,2,6-trimethylcyclohexanone/ml was produced almost stoichiometrically, with 94% enantiomeric excess in the presence of glucose, NAD⁺, and glucose dehydrogenase. To our knowledge, this is the first report of the application of S. cerevisiae old yellow enzyme for the production of a useful compound.     

Secretory type of recombinant thioredoxin h induces ER stress in endosperm cells of transgenic rice

Thioredoxin h (TRX h) functions as a reducing protein and is present in all organisms. As a new approach for inducing the endoplasmic reticulum (ER) stress, TRX h (OsTRX23) was expressed as a secretory protein using the endosperm-specific glutelin GluB-1 promoter and a signal peptide. In transgenic rice seeds, the majority of the recombinant TRX h accumulated in the ER but some was also localized to the protein body IIs (PB-IIs). The rice grain quality was dependent on the TRX h accumulation level. Increased TRX h expression resulted in aberrant phenotypes, such as chalky and shriveled features, lower seed weight and lower seed protein content. Furthermore, the accumulation of some seed storage proteins (SSPs) was significantly suppressed and the morphology of the protein bodies (PB-Is and PB-IIs) changed according to the level of TRX h. SSPs, such as 13 kDa prolamin and GluA, were specifically modified via the reducing action of TRX h. These changes led to the activation of the ER stress response, which was accompanied by the expression of several chaperone proteins. Specifically, the ER stress markers BiP4 and BiP5 were significantly up-regulated by an increase in the level of TRX h. These results suggest that changes in the conformation of certain SSPs via the action of recombinant TRX h lead to an induced ER stress response in transgenic rice seeds.     

Membranous Structure of Purified Escherichia coli Lipopolysaccharide

The ultrastructure of the purified and lyophilized endotoxin from Escherichia coli O111 was observed by ultrathin sectioning. Onion-like globular membrane structures were observed in addition to rod-like and ribbon-like structures, indicating the existence of a globular membrane structure even in the dried state.     

Ancient Mitochondrial DNA Reveals the Origin of Sus scrofa from Rebun Island, Japan

The Kabukai A site (5 to 8C A.D.) of the Okhotsk cultural area is on Rebun Island, a small island near the coast, north–northwest of Hokkaido, Japan. Specimens of Sus scrofa, called the Sakhalin pig, were discovered in five cultural layers at the Kabukai A site. Ancient DNA was extracted from the remains of 42 Sakhalin pig bones. Thirty-nine nucleotide sequences of the 574-bp mitochondrial DNA control region, estimated to have originated from at least 21 individuals, were amplified and analyzed phylogenetically. Nine distinct haplotypes (A1, A2, A3, B1, B2, C1, C2, D1, and D2) from this site were classified into four haplotype groups (A, B, C, and D) by parsimonious network analysis. Phylogenetic analysis of 9 ancient and 55 modern haplotypes indicated that the population of Sakhalin pigs at the Kabukai A site belonged to two distinct clusters; haplotype groups A and B formed a cluster comprised only of themselves, and haplotype groups C and D belonged to the cluster of one of the two genetic groups of Japanese wild boars uniquely distributed in the western part of Japan, including one northeast Mongolian wild boar. Analysis of the haplotype distribution among three archaeological sites and their historical transitions among the five layers reflecting the cultural periods at the Kabukai A site suggests that the Sakhalin pig populations were introduced from Sakhalin island and the Amur River basin in the northeastern Eurasian continent together with some cultural influences. Received: 18 April 2000 / Accepted: 24 November 2000