Suitability of Japanese codling as a raw material for surimi-based products revealed by primary sequence analysis of myosin heavy chain and thermal gel properties

Fisheries Science - Complementary DNA encoding a part of myosin heavy chain was cloned from fast skeletal muscle of Japanese codling Physiculus japonicus. Japanese codling, a frequent catch off the...     

Biochemical changes in oyster tissues and hemolymph during long-term air exposure

The Pacific oyster Crassostrea gigas is a sessile bivalve that inhabits the intertidal zone and therefore frequently exposed to air during the tidal cycle. It is highly adaptive to hypoxic conditions. We have studied the physiological state of oysters during long-term exposure to air. The oysters became hypoxic when exposed to air or hypoxic seawater. The 50% lethal time of oysters exposed to air at 4, 15 and 20°C was 47.8, 15.9 and 12.2 days, respectively. The hemolymph pH decreased by day 3; however, it showed a slight increase by day 5 at both 4 and 20°C. The adenylate energy charge (AEC) values decreased rapidly on the first day of air exposure in the adductor muscle, mantle, gill and body trunk, and these decreases were accompanied by decreases in ATP concentrations and increases in AMP concentrations. The AEC values in all of the tissues had fallen to below 30% by day 50 of air exposure at 4°C. These data suggest that the energy state of oysters deteriorates rapidly with air exposure. Consequently, AEC values may be useful indices of the physiological state of the oyster during long-term exposure to air.     

Hot-water solubility of mantle collagens in several cephalopod molluscs

The mantle muscles of five cephalopod species, Todarodes pacificus, Photololigo edulis, Sepioteuthis lessoniana, Sepia esculenta, and Sepia longipes, were extracted with 0.1 M NaOH to prepare crude collagen fiber, called ‘residue after alkali extraction’ (RS-AL). Solubility of the collagens in water was examined in the temperature range 20–90°C. The collagens showed a similar tendency in solubility, which gradually increased depending on the treating temperature, and the values at 40–90°C were constantly less than 47.0% for all the species examined. In addition, the collagens were estimated to denature in the approximate temperature range of 37.5–42.5°C. These results suggest that the collagens in RS-AL from these species may have relatively high resistance to hot-water extraction even after their denaturation.     

Genetic analysis of host–pathogen incompatibility between Lolium isolates of Pyricularia oryzae and wheat

Lolium isolate TP2 of Pyricularia oryzae, causal agent of gray leaf spot of perennial ryegrass (Lolium perenne), is virulent on perennial ryegrass, but avirulent on wheat cultivars. Genetic analysis of wheat F₂ populations revealed that the resistance of wheat cultivars Chinese Spring, Shin-chunaga, and Norin 4 to TP2 was conditioned by two genes, R1 and R2. R1 was highly effective, while R2 was less effective. The strong resistance gene R1, designated Rmg6, was mapped on chromosome 1D using microsatellite markers. For revealing genetic mechanisms of avirulence, TP2 was crossed with Triticum isolate Br48. Segregation analysis of their F₁ progenies revealed that the avirulence of TP2 on the three wheat cultivars was conditioned by two unlinked genes, one (A1) highly effective and the other (A2) less effective. These results suggest that the incompatibility between TP2 and the common wheat cultivars is conditioned by two gene pairs; the Rmg6–A1 interaction results in strong resistance, and the R2–A2 interaction results in moderate resistance.     

Enzymatic solubilization of collagen in the skin of diamond squid Thysanoteuthis rhombus: application of a fungal acid protease

Enzymatic solubilization of collagen from the skin tissue of diamond squid Thysanoteuthis rhombus, an underutilized resource in Japan, was attempted using an acid protease from the fungus Rhizopus niveus. This novel approach was compared with the conventional method using porcine pepsin. Both proteases were able to solubilize most of the skin collagen (>90 % of the total collagen) by performing the treatment in 0.5 M acetic acid at 4 °C for 72 h and at an enzyme/substrate ratio (w/w) of 1/10. The SDS-PAGE patterns of the solubilized collagen preparations were quite similar to each other, and two types of collagen (major and minor collagens) were purified from each preparation by cation-exchange column chromatography. These collagen types from the porcine pepsin-solubilized collagen showed similar features to those from the Rhizopus acid protease-solubilized collagen. These results suggest that the Rhizopus acid protease, a protease of non-animal origin, is applicable for solubilizing collagen in the skin of diamond squid.     

Purification and characterization of a lectin from the starfish Asterias amurensis

In this study, we describe a novel lectin (designated AMUL) from the Northern Pacific starfish Asterias amurensis. AMUL was purified from the coelomic fluid by affinity chromatography followed by size-exclusion chromatography. The native molecular mass of the lectin was found to be approximately 270 kDa by size-exclusion chromatography using a Superdex 200 column. AMUL showed distinct bands at approximately 14 or 18 kDa on SDS-PAGE under nonreducing or reducing conditions, respectively. The hemagglutination activity of AMUL against rabbit erythrocytes was strongly inhibited by the two sialic acids N-acetylneuraminic acid and N-glycolylneuraminic acid. The glycoproteins tested showed no inhibition of hemagglutination. The first 28 amino acid residues of AMUL were determined by automated Edman degradation, showing that AMUL has considerable sequence homology with C-type lectins from other echinoderms. These results show that AMUL is a novel echinoderm-derived sialic-acid-specific lectin that belongs to the C-type lectin superfamily.     

Changes in fructooligosaccaride composition and related enzyme activities of burdock root during low-temperature storage

Changes in the composition of fructooligosaccarides (FOSs) and related enzyme activities of burdock root during low-temperature storage (1 °C) were measured. Burdock root is composed of monosaccharides, such as glucose and fructose, disaccharides, such as sucrose, and FOS in the extracted carbohydrates. The composition was the highest in fructose, followed by sucrose, FOS, and glucose. The FOS composition was the highest in 1-kestose, followed by nystose and 1-fructofuranosyl nystose. The fructose and glucose contents in burdock root during storage at 1 °C decreased significantly, whereas the sucrose content increased sharply. In contrast, the 1-kestose, nystose, and 1-fructofuranosyl nystose contents significantly increased. The activities of sucrose:sucrose 1-fructosyl transferase (1-SST) and fructan:fructan 1-fructosyl transferase (1-FFT) increased sharply and then gradually decreased, and they were closely related to the changes in FOS content. However, the activity of fructan 1-exohydrolase (1-FEH) was constant. These results indicate that changes in the FOS composition and related enzyme activities of burdock root might be related to low temperature during long term storage.     

Overexpression of a fungal laccase gene induces nondehiscent anthers and morphological changes in flowers of transgenic tobacco

Laccases play important roles in the development of fruiting bodies and in lignin degradation by basidiomycetes. In this study, we present novel phenotypes of transgenic tobacco plants with a chimeric gene for fungal laccase under the control of the cauliflower mosaic virus 35S promoter. At the flowering stage, the transgenic plants that produced recombinant laccase had brownish anthers instead of the greenish anthers of wild-type plants. The brownish anthers exhibited male sterility with a nondehiscent phenotype at varying frequencies. The frequency of nondehiscence depended on the temperature at which plants were cultivated and it was higher at 24°C than at 29°C. The cell wall structures of transgenic anther tissues were almost the same as in the wild type, but the stomium was severely deformed, and abnormal components were apparent in cells of the endothecium and epidermis. Furthermore, the pattern of deposition of flavonoids in the transgenic anther epidermis differed from the wild-type pattern. The expression of laccase also induced other phenotypic changes in the flowers of transgenic plants, namely, increased petal number, fused and petaloid stamens, and doubling of floral organs. These results indicate that the ectopic expression of laccase influences various aspects of flower development.     

Root pruning is effective in alleviating the inhibition of soybean growth caused by anaerobic stress for a short period

Soybean is an important upland crop,but its productivity is often limited by anaerobic stress caused by waterlogging.The ability to adjust root growth under environmental constraints is an important physiological trait for adapting to an everchanging environment,and root pruning is an artificial technique for regenerating the root system.In the present study,we investigated whether root pruning in soybean can effectively alleviate the inhibitory effects of anaerobic stress.Soybean plants were af...     

Identification of overwintering vegetative cells of the bivalve-killing dinoflagellate <Emphasis Type="Italic">Heterocapsa circularisquama</Emphasis> in Uranouchi Inlet,Kochi Prefecture,Japan

ABSTRACT:   Red tides of Heterocapsa circularisquama have led to serious damage of bivalve aquacultures in western coastal areas of Japan. To understand the whole picture regarding the ecology of this species, it is essential to clarify its overwintering mechanisms. In this study, the population dynamics of H. circularisquama were investigated from February 2004 to November 2005, and overwintering cells were identified for the first time in water columns of Uranouchi Inlet, Kochi Prefecture, Japan. Heterocapsa circularisquama cells were detected by the indirect fluorescent antibody technique using monoclonal antibodies that specifically recognize and react to this species. Vegetative cells were almost always detected from the first observation in February 2004 to November 2005 with temperatures of 10.5–30.6°C. During the period from winter to spring, this species survived in areas with a temperature higher than 10°C. The overwintering cells of H. circularisquama were isolated in March 2004, and identification was made via observation of the morphology and body scales of the cultured cells. These overwintering cells were identified as H. circularisquama and reacted to the monoclonal antibody. These results indicate that H. circularisquama can overwinter and survive throughout the year in a vegetative cell state in Uranouchi Inlet.