Melting behaviour of a triple helical polysaccharide schizophyllan in aqueous solution

Two sonicated samples of schizophyllan in aqueous solution at temperatures from 20 to 160°C were investigated by viscometry. The temperature dependence of the viscosity coefficient η showed that schizophyllan in water undergoes an irreversible thermal transition at about 135°C. The values of $\text{(ln η}{}_{\mathrm{r}}\text{)}\text{c}$ (ηr is the relative viscosity and c is the polymer concentration (w/v)) at 25°C determined after preheating aqueous schizophyllan indicated that the major conformations of schizophyllan in water at 120 and 150°C are triple helix and single random coil, respectively. Thus, it was concluded that the change in η at about 135°C with an increase in temperature is due to the melting of triple helices to single chains. Schizophyllan denatured to single chains at about 150°C did not restore the intact triple helix, but formed aggregates, when the solution was cooled to 25°C. It was also found that the aggregates form a gel when c is higher than a certain value.     

Structural analysis of four large plasmids harboring in a unicellular cyanobacterium, Synechocystis sp. PCC 6803.

The genome of the unicellular cyanobacterium Synechocystis sp. PCC 6803 consists of a single chromosome and several plasmids of different sizes, and the nucleotide sequences of the chromosome and three small plasmids (5.2 kb, 2.4 kb, and 2.3 kb) have already been sequenced. We newly determined the nucleotide sequences of four large plasmids, which have been identified in our laboratory (pSYSM:120 kb, pSYSX:106 kb, pSYSA:103 kb, and pSYSG:44 kb). Computer-aided analysis was performed to explore the genetic information carried by these plasmids. A total of 397 potential protein-encoding genes were predicted, but little information was obtained about the functional relationship of plasmids to host cell, as a large portion of the predicted genes (77%) were of unknown function. The occurrence of the potential genes on plasmids was divergent, and parA was the only gene common to all four large plasmids. The distribution data of a Cyanobacterium-specific sequence (HIP1: 5'-GCGATCGC-3') suggested that respective plasmids could have originated from different cyanobacterial strains.     

Relationships among growth and different NOR phenotypes in a specific stock of rainbow trout (Oncorhynchus mykiss).

Growth is one of the most important aspects in the genetic improvement of cultured fish species. Consequently, genetic parameters related to this feature and their response to selection have been the focus of most research in this area. Such research indicates that, in general, there is enough additive genetic variance related to growth, justifying the use of selection. Based on the usefulness of cytogenetic and molecular markers in the fish culture, the aim of the present work was to analyze the possible relationships among cytogenetic characteristics, specifically the NOR phenotypes, and the increase in length and weight in specimens of the rainbow trout (Oncorhynchus mykiss), resultant from directed mating between homozygous females and heterozygous males according to their NOR phenotypic patterns. The equations of the relationship between length and weight of the analyzed specimens followed the model Wt = a Lt(b), showing b values higher than 3, determinant of a positive allometric growth. The results showed that the different NOR phenotypes were not related with the growth values for length and weight in any statistical test.     

Sex pheromone production and perception in the mating disruption-resistant strain of the smaller tea leafroller moth, Adoxophyes honmai

Mating disruption is an environmentally safe plant protection strategy that uses a synthetic copy of an insect pheromone to interfere with sexual communication and hence reproduction. To date, a number of pest moths have been controlled with applications of formulated pheromones as mating disruptants. Recently, however, the first example of resistance to mating disruption was documented in one of the major tea pests in Japan, the smaller tea leafroller moth, Adoxophyes honmai Yasuda (Lepidoptera: Tortricidae). To avoid other such cases, it is important to elucidate the mechanism(s) by which the disruptant lost its effectiveness. To this end, we imposed further selection by rearing field‐collected resistant insects with a synthetic pheromone in the laboratory. After more than 70 generations of selection, a strain with quite strong resistance was established, males of which could find and copulate with their mates even in the presence of 1 mg l^?1 of disruptant. Although the mating ability of this strain was greatly increased, the composition and blend ratio of the sex pheromone produced and emitted by females were not obviously changed in comparison with those of females sensitive to mating disruption. However, male response to the pheromone blend was markedly broadened after selection so that resistant males could locate a synthetic pheromone source even when it lacked a pheromone component that is normally necessary for attraction. Males capable of locking onto off‐ratio pheromone blends may be better able to find calling females in pheromone‐treated environments than narrowly tuned males because of greater capability of overcoming sensory imbalance.     

Methoxyflavones protect cells against endoplasmic reticulum stress and neurotoxin

Enhanced endoplasmic reticulum (ER) stress leads to cell death in various pathophysiological situations. During a search for compounds that regulate ER stress, we identified methoxyflavones, a group of flavonoids, as strong protective agents against ER stress. Analysis in mouse insulinoma MIN6 cells revealed that methoxyflavones mildly activated the eukaryotic initiation factor 2 and nuclear factor erythroid 2-related factor pathways, but not the XBP1 pathway, and induced downstream genes, including glucose-regulated protein (GRP) 78, a molecular chaperone in the ER. The protective effect of methoxyflavones was enhanced by agents that increase intracellular cAMP levels such as forskolin, dibutyryl-cAMP and IBMX, but suppressed by the protein kinase A (PKA) inhibitor H-89, suggesting involvement of the PKA pathway in the regulation of ER stress by methoxyflavones. Consistent with the results in cultured cells, pretreatment of mice with tangeretin, a methoxyflavone, enhanced expression of GRP78 and HO-1 without causing ER stress in renal tubular epithelium and prevented tunicamycin-induced cell death. Furthermore, preadministration of tangeretin in mice enhanced expression of GRP78 in the substantia nigra pars compacta and protected dopaminergic neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a neurotoxin that induces both oxidative and ER stress. These results suggest that methoxyflavones play an important role in the regulation of ER stress and could be a therapeutic target for the ER stress-related diseases. neuronal degeneration; flavonoids     

Improved Gateway binary vectors: high-performance vectors for creation of fusion constructs in transgenic analysis of plants

We made a series of improved Gateway binary vectors (pGWBs) for plant transformation. Fifteen different reporters and tags, sGFP, GUS, LUC, EYFP, ECFP, G3GFP, mRFP, 6xHis, FLAG, 3xHA, 4xMyc, 10xMyc, GST, T7, and TAP, were employed. Some vectors carry the 2x35S-Omega promoter for higher-level expression. The kanamycin- and hygromycin-resistant markers are independently available for each of the 43 types of vectors, thus an additional transformation of once-transformed plants can be carried out easily. Their small size and high-copy number in Escherichia coli make possible easier handling at plasmid preparation and sequencing. Improved pGWBs should be a powerful tool for transgenic research in plants.     

Selection for functional diversity drives accumulation of point mutations in Dr adhesins of Escherichia coli

Immune escape is considered to be the driving force behind structural variability of major antigens on the surface of bacterial pathogens, such as fimbriae. In the Dr family of Escherichia coli adhesins, structural and adhesive functions are carried out by the same subunit. Dr adhesins have been shown to bind decay-accelerating factor (DAF), collagen IV, and carcinoembryonic antigen-related cell adhesion molecules (CEACAMs). We show that genes encoding Dr adhesins from 100 E. coli strains form eight structural groups with a high level of amino acid sequence diversity between them. However, genes comprising each group differ from each other by only a small number of point mutations. Out of 66 polymorphisms identified within the groups, only three were synonymous mutations, indicating strong positive selection for amino acid replacements. Functional analysis of intragroup variants comprising the Dr haemagglutinin (DraE) group revealed that the point mutations result in distinctly different binding phenotypes, with a tendency of increased affinity to DAF, decreased sensitivity of DAF binding to inhibition by chloramphenicol, and loss of binding capability to collagen, CEACAM3 and CEACAM6. Thus, variability by point mutation of major antigenic proteins on the bacterial surface can be a signature of selection for functional modification.     

Complete structure of the chloroplast genome of a legume, Lotus japonicus.

The nucleotide sequence of the entire chloroplast genome (150,519 bp) of a legume, Lotus japonicus, has been determined. The circular double-stranded DNA contains a pair of inverted repeats of 25,156 bp which are separated by a small and a large single copy region of 18,271 bp and 81,936 bp, respectively. A total of 84 predicted protein-coding genes including 7 genes duplicated in the inverted repeat regions, 4 ribosomal RNA genes and 37 tRNA genes (30 gene species) representing 20 amino acids species were assigned on the genome based on similarity to genes previously identified in other chloroplasts. All the predicted genes were conserved among dicot plants except that rpl22, a gene encoding chloroplast ribosomal protein CL22, was missing in L. japonicus. Inversion of a 51-kb segment spanning rbcL to rpsl6 (positions 5161-56,176) in the large single copy region was observed in the chloroplast genome of L. japonicus. The sequence data and gene information are available on our World Wide Web database at http://www.kazusa.or.jp/en/plant/database.html.     

Generation of 10,154 expressed sequence tags from a leafy gametophyte of a marine red alga, Porphyra yezoensis.

A total of 10,154 5'-end expressed sequence tags (EST) were established from the normalized and size-selected cDNA libraries of a marine red alga, Porphyra yezoensis. Among the ESTs, 2140 were unique species, and the remaining 8014 were grouped into 1127 species. Database search of the 3267 non-redundant ESTs by BLAST algorithm showed that the sequences of 1080 species (33.1%) have similarity to those of registered genes from various organisms including higher plants, mammals, yeasts, and cyanobacteria, while 2187 (66.9%) are novel. Codon usage analysis in the coding regions of 101 non-redundant EST groups showing significant similarity to known genes indicated the higher GC contents at the third position of codons (79.4%) than the first (62.2%) and the second position (45.0%), suggesting that the genome has been exposed to high GC pressure during evolution. The sequence data of individual ESTs are available at the web site http://www.kazusa.or.jp/en/plant/porphyra/EST/.