Isolation and characterization of the rbcS genes from a sterile mutant of Ulva pertusa (Ulvales,Chlorophyta) and transient gene expression using the rbcS gene promoter

We isolated two different genomic DNAs (UprbcS1 and UprbcS2) encoding the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase and portions of the 5′- and 3′-flanking regions from sterile Ulva pertusa Kjellman. The UprbcS1 and UprbcS2 genes had three introns in the coding region. Each predicted UprbcS polypeptide was a 180-amino-acid (AA) residue including a 38-AA transit peptide, although the 104th AA residue was replaced. The nucleotide sequences of UprbcS cDNAs isolated from a cDNA library corresponded to that of the UprbcS1 gene, suggesting that the UprbcS1 gene was predominantly expressed in sterile U. pertusa compared to UprbcS2. Southern blot analysis showed that each UprbcS gene was a single-copy gene in the sterile U. pertusa genome. Northern hybridization indicated that the expression of UprbcS was induced and repressed by dark and light treatments, respectively. When sterile U. pertusa cells were transformed with an expression vector containing the UprbcS1 promoter and terminator sequences fused with the green fluorescent protein (GFP) gene, GFP fluorescence was observed in the cells transformed. These results suggest that the UprbcS1 gene promoter is light regulated and highly active in the sterile U. pertusa cells and is available for genetic transformation system in the alga.     

Complete mitochondrial DNA sequence of ayu Plecoglossus altivelis

SUMMARY: We determined the complete nucleotide sequence of the mitochondrial genome for ayu, Plecoglossus altivelis . Two large DNA fragments covering the entire genome were amplified using a long polymerase chain reaction (PCR) technique, and the products subsequently used as templates for PCR with 57 fish-versatile and five species-specific primers that amplify contiguous, overlapping segments of the entire genome. Direct sequencing of the PCR products demonstrated that the genome (16 537 bp) contained the same 37 mitochondrial genes (two ribosomal RNA, 22 transfer RNA, and 13 protein-coding genes) as those found in other vertebrates, with the gene order identical to that in typical vertebrates. A major non-coding region between the tRNA^Pro and tRNA^Phe genes (857 bp) was considered to be the control region (D-loop), as it has several conservative blocks that are characteristic to this region.     

Effect of dietary taurine levels on growth and feeding behavior of juvenile Japanese flounder Paralichthys olivaceus

This study was conducted to investigate the effect of dietary taurine levels on growth and feeding behavior of juvenile Japanese flounder. Three different taurine level diets were prepared by supplementation of taurine (T-0%, 0.5% and 1.5%) to the basal diet. Fish meal washed with 70% ethanol to remove taurine was used as the sole protein source. Feeding experiments were carried out twice at 20 °C by using different size of fish (average body weight: 0.3 g in Experiment I and 3.7 g in Experiment II). The feeding behavior of fish was observed throughout the experimental period. At the end of experiments, fish were killed for amino acids analysis.

The final average body weight and feed efficiency of juvenile Japanese flounder fed the T-1.5% diet was significantly higher than those of fish fed the T-0% diet in Experiments I and II. Abnormal feeding behavior such as multiple feeding while swimming in the water column was observed in the T-0% group in Experiment I. These findings indicate that taurine is essential for normal growth and development of normal feeding behavior of juvenile Japanese flounder.     

Effects of thyroid hormone on gonadotropin-induced steroid production in medaka,Oryzias latipes,ovarian follicles

Blood and ovarian samples were collected at intervals of 4h prior to spawning time from medaka (Oryzias latipes) that were maturationally synchronized with artificial photoperiod (14h light: 10h dark). Plasma estradiol-17β (E₂) levels increased rapidly from 16h before spawning and peaked at 8h before spawning. Follicle-enclosed oocytes (ovarian follicles) at different stages of development were isolated from the ovaries and used to study the in vitro effects of thyroid hormone (triiodothyronine; T₃) on pregnant mare serum gonadotropin (GTH)-induced E₂ production. GTH at a concentration of 100 IU/ml stimulated E₂ production by ovarian follicles collected between 32 and 16h before spawning. At 32h before spawning, T₃ (5 ng/ml) administered along with GTH (100 IU/ml) resulted in a 3.5 fold increase in E₂ production, compared with GTH administered alone. These results suggest that T₃ can act on ovarian follicles directly to modulate GTH-stimulated E₂ production in the medaka.