Enhancement of red-light-induced anthocyanin synthesis in sorghum first internodes by moderate low temperature given in the pre-irradiation culture period

Anthocyanin synthesis in the broom sorghum, Sorghum bicolor Moench cvs. Acme Broomcorn and Sekishokuzairai-Fukuyama, is mediated separately or synergistically by an ultraviolet light-B (UV-B) photoreceptor and phytochrome. When seedlings were exposed to moderate low temperatures ranging from 12 to 20° C before irradiation, only the phytochrome-mediated anthocyanin synthesis was markedly enhanced compared with the control, which was kept throughout at 24° C; synthesis mediated by the UV-B photoreceptor was unaffected. The effectiveness of an exposure to 20° C increased as the duration of exposure increased up to 24 h and as the time of exposure became closer to the time of irradiation. However, when seedlings were exposed to 20° C from after irradiation until harvest, anthocyanin syntheses induced by both UV-B and red light were equally suppressed, probably due to the general reduction of metabolism involved in anthocyanin synthesis that is a consequence of lower temperature. The results support the view that the signal transduction of the pyhtochrome system is different from that of the UV-B photoreceptor, and indicate that the phytochrome system may involve a step or steps which are amplified by a previous exposure to the moderate low temperature.Abbreviations FR far-red light - LT low temperature - MLT moderate low temperature - Pfr far-red-light-absorbing form of phytochrome - R red light - UV ultraviolet light - UV-B ultraviolet light-B We thank Drs. Y. Takeuchi (Shionogi Pharmaceutical Company, Aburahi, Shiga) and K. Hosaka (the Experimental Farm, Kobe University, Kasai) for seeds; Dr. M. Watanabe and Mr. M. Kubota (the National Institute for Basic Biology, Okazaki) for operation of the spectrograph. This work was supported by grants from the Yamada Science Foundation, Ministry of Education (No. 63480015 and 03454048), and the National Institute for Basic Biology (Large Spectrograph grant No. 91-523).     

Biochemical roles of the oligosaccharide chains in thyrostimulin, a heterodimeric hormone of glycoprotein hormone subunits alpha 2 (GPA2) and beta 5 (GPB5)

Thyrostimulin is a heterodimeric hormone composed of GPA2 and GPB5, and shares the thyroid-stimulating hormone receptor (TSHR). Thyrostimulin has three N-linked oligosaccharide chains, two in GPA2 and one in GPB5. The roles of these N-linked oligosaccharides in secretion, heterodimer formation and signal transduction were analyzed. Recombinant GPA2s lacking either of the two oligosaccharides were obtained from conditioned medium, whereas dual site-disrupted GPA2 and the GPB5 mutant were not expressed in either the conditioned medium or cell lysate. The binding between GPA2 and GPB5 was weaker than that between TSH subunits GPA1 and TSH beta. Neither of the oligosaccharides in GPA2 had significant effects on heterodimerization. Disruption of either of the oligosaccharides in GPA2 significantly decreased receptor activation, suggesting their critical role in receptor activation.     

Hypomethylation of paternal DNA in the late mouse zygote is not essential for development

Global demethylation of DNA which marks the onset of development occurs asynchronously in the mouse; paternal DNA is demethylated at the the zygote stage, whereas maternal DNA is demethylated later in development. The biological function of such asymmetry and its underlying mechanisms are currently unknown. To test the hypothesis that the early demethylation of male DNA may be associated with protamine-histone exchange, we ,used round spermatids, whose DNA is still associated with histones, for artificial fertilization (round spermatid injection or ROSI), and compared the level of methylation of metaphase chromosomes in the resulting zygotes with the level of methylation in zygotes obtained after fertilization using mature sperm heads (intracytoplasmic sperm injection or ICSI). In contrast to ICSI-derived zygotes, ROSI-derived zygotes possessed only slightly demethylated paternal DNA. Both types of zygotes developed to term with similar rates which shows that hypomethylation of paternal DNA at the zygotic metaphase is not essential for full development in mice. Incorporation of exogenously expressed histone H2BYFP into paternal pronuclei was significantly higher in ICSI-derived zygotes than in ROSI-derived zygotes. Surprisingly, in the latter the incorporation of histone H2BYFP into the paternal pronucleus was still significantly higher than into the maternal pronucleus, suggesting that some exchange of chromatin-associated proteins occurs not only after ICSI but also after ROSI. This may explain why after ROSI, some transient demethylation of paternal DNA occurs early after fertilization, thus providing support for the hypothesis regarding the link between paternal DNA demethylation and protamine/histone exchange.     

Anti-diabetic effects of globin digest and its active ingredient Leu-Ser-Glu-Leu in ICR mice,streptozotocin-induced diabetic mice and KK-Ay mice

AimsLeu-Ser-Glu-Leu (LSEL) is the main active ingredient of globin digest (GD) that has an anti-diabetic effect. Here, we investigated the anti-diabetic effect of LSEL for the first time.Main methodsThe anti-diabetic effects of GD and LSEL in ICR mice, streptozotocin (STZ)-induced diabetic mice and KK-Ay mice were examined.Key findingsGD and LSEL suppressed the elevation of blood glucose in an oral glucose tolerance test (OGTT) in ICR mice, STZ-induced diabetic mice and KK-Ay mice as well as in an oral sucrose tolerance test in ICR mice and in an insulin tolerance test (ITT) in KK-Ay mice. GD and LSEL decreased the blood glucose levels in the basal state in STZ-induced diabetic mice and KK-Ay mice. Furthermore, GD and LSEL elevated the serum insulin levels in an OGTT in ICR mice and KK-Ay mice and promoted the use of insulin in an ITT in KK-Ay mice. GD and LSEL increased the translocation or expression of the glucose transporter 4 in the muscle of ICR mice, STZ-induced diabetic mice and KK-Ay mice and increased the expression of the uncoupling protein 2 (UCP2) in the muscle of ICR mice.SignificanceThese results indicate that GD and LSEL control blood glucose through the promotion of glucose uptake in the muscle of the mice. The acceleration of glucose uptake by GD and LSEL may be controlled by the promotion of insulin secretion and the up-regulation of UCP2 expression. GD and LSEL seem to be useful for lowering the incidence of hyperglycemia.     

Genetic characteristics of endangered Japanese golden eagles (Aquila chrysaetos japonica) based on mitochondrial DNA D-loop sequences and karyotypes

Mitochondrial DNA D-loop sequences (472 bases) for endangered Japanese golden eagles (Aquila chrysaetos japonica) were investigated to evaluate-intrapopulational genetic variations. Among 23 golden eagles, including origin-known eagles caught in the wild and origin-unknown eagles, 10 variable sites were found in the 472 base-sequences. From the nucleotide substitutions, five haplotypes of D-loop sequences were identified, indicating the occurrence of at least three maternal lineages in golden eagles around Japan. Distribution patterns of D-loop haplotypes suggested a wide genetic communication between local populations around Japan prior to a recent habitat fragmentation and a decrease in the population size. In addition, cytogenetic analysis showed that a karyotype specific to the Japanese golden eagle is consistently 2n=62 including eight microchromosomes. Based on mitochondrial DNA and karyotype data, it is likely that golden eagle populations from Japan and the Korean Peninsula together form a common conservation unit. These results provide an important framework for conservation actions for Japanese golden eagle populations in zoos, and in situ reintroduction and translocation programs. Zoo Biol 17:111–121, 1998. © 1998 Wiley-Liss, Inc.     

Molecular cytogenetic characterization of Ciona intestinalis chromosomes

The compact genome of the ascidian Ciona intestinalis has been sequenced. Chromosome karyotype and mapping of the genome sequence information on each of the 14 pairs of chromosomes are essential for genome-wide studies of gene expression and function in this basal chordate. Although the small chromosome size (most pairs measuring less than 2 mum) complicates accurate chromosome pairing based on morphology alone, the present results suggest that 20 chromosomes are metacentric and 8 are submetacentric or subtelocentric, and two pairs of large chromosomes (#1 and #2) were defined. The characterization of chromosomes by FISH and staining with propidium iodide indicated that 18S/28S ribosomal gene repeats are present in the short arms of three pairs of chromosomes and that the short arms of these pairs show remarkable size polymorphism. In addition, each chromosome was characterized molecular cytogenetically by mapping representative BAC clones with FISH. The present study is therefore a first step in expanding the karyotype analysis and entire physical mapping of the genome sequence of Ciona intestinalis.     

Effect of globin digest on the liver injury and hepatic gene expression profile in galactosamine-induced liver injury in SD rats

AimsWe investigated the effect of globin digest (GD) on the liver injury and hepatic gene expression profile in galactosamine (GalN)-induced liver injury.Main methodsThe effect of GD on the liver injury was examined by measuring the activities of serum transferases and hepatic antioxidant enzymes, histopathological analysis, gene expression profile, and proteins of the peroxisome proliferator-activated receptor alpha (PPARα) and met proto-oncogene (c-Met) in SD rats at 24 h after GalN administration. The effect of GD on the expression of PPARα and its target gene in AML-12 mouse hepatocytes was also examined.Key findingsGD suppressed the elevated activities of serum transferases in GalN-induced liver injury in SD rats. The thiobarbituric acid reactive substance content in GalN-injured liver was a decreasing tendency by GD. GD suppressed the increased oxidized glutathione content, and increased the decreased protein, reduced glutathione contents, and catalase activity in GalN-injured liver. GD may improve the antioxidant defense system and protein synthesis in GalN-injured liver. GD suppressed the elevated expression of the genes related to the inflammation, and decreased the histopathological grade value of inflammatory cell infiltration in GalN-injured liver. GD increased the expression of PPARα protein in GalN-injured liver, and also increased the expression of PPARα and its target gene in AML-12 hepatocytes. The total and phosphorylated c-Met proteins in GalN-injured liver were the increasing tendencies by GD.SignificanceThese findings indicate that GD has the hepatoprotective effect on GalN-induced liver injury in SD rats.     

Comparison of the Z and W sex chromosomal architectures in elegant crested tinamou (<Emphasis Type="Italic">Eudromia elegans</Emphasis>) and ostrich (<Emphasis Type="Italic">Struthio camelus</Emphasis>) and the process of sex chromosome differentiation in palaeognathous birds

To clarify the process of avian sex chromosome differentiation in palaeognathous birds, we performed molecular and cytogenetic characterization of W chromosome-specific repetitive DNA sequences for elegant crested tinamou (Eudromia elegans, Tinamiformes) and constructed comparative cytogenetic maps of the Z and W chromosomes with nine chicken Z-linked gene homologues for E. elegans and ostrich (Struthio camelus, Struthioniformes). A novel family of W-specific repetitive sequences isolated from E. elegans was found to be composed of guanine- and cytosine-rich 293-bp elements that were tandemly arrayed in the genome as satellite DNA. No nucleotide sequence homologies were found for the Struthioniformes and neognathous birds. The comparative cytogenetic maps of the Z and W chromosomes of E. elegans and S. camelus revealed that there are partial deletions in the proximal regions of the W chromosomes in the two species, and the W chromosome is more differentiated in E. elegans than in S. camelus. These results suggest that a deletion firstly occurred in the proximal region close to the centromere of the acrocentric proto-W chromosome and advanced toward the distal region. In E. elegans, the W-specific repeated sequence elements were amplified site-specifically after deletion of a large part of the W chromosome occurred.