Expression of theRSI-1 gene during development of roots and reproductive organs in tomato

TheRSI-1 gene is expressed in pericycle cells just prior to the first round of cell division for lateral root development in tomato. We transformed tomato plants with theRSI-1 gene promoter linked to a GUS reporter gene. GUS activity was detected not only at the sites of initiation for lateral and adventitious roots, but also at the primary root tip. Expression of the fusion gene was also regulated at various stages of tissue development: in particular, during the formation of reproductive organs such as pollen and fruit Overexpression of theRSI-1 gene in either the sense or antisense orientation resulted in arrest of fruit development and seed germination. TheRSI-1 gene product, therefore, may play a role in auxin-induced cell division in various developing tissues. Inter and intramolecular disulfide bridges between cysteines rich in the RSI-1 protein might be involved in cell-wall modifications that are essential for new cell division. These hypotheses for the role of theRSI-1 gene in lateral-root and reproductive-organ development remain to be tested.     

Overexpression of insulin-like growth factor (IGF)-I receptor enhances inhibition of DNA replication in mouse cells exposed to x-rays

Previous studies from our laboratory provided evidence for the operation of signal transduction pathways involving ras, myc, and staurosporine-sensitive protein kinases in the regulation of DNA replication in irradiated cells. Because ras and myc are also involved in the signal transduction elicited in response to ligand activation of growth factor receptors, we wondered whether growth factor receptors are upstream elements in the regulation of DNA replication in irradiated cells. Here, we report on the role of insulin-like growth factor I receptor (IGF-IR) in the regulation of DNA replication in irradiated cells. We compare radiation-induced inhibition of DNA replication in BALB/c 3T3 cells with that in P6 cells. P6 cells are derived from BALB/c 3T3 cells by transfection with a vector expressing IGF-IR, leading to 30-fold overexpression. We observe a significantly stronger inhibition of DNA replication after irradiation in P6 as compared with BALB/c 3T3 cells at all doses examined. Sedimentation in alkaline sucrose gradients shows that the increased inhibition in P6 cells is due to an increased inhibition of replicon initiation, the main controlling event in DNA replication. Staurosporine at 20 nM reduces radiation-induced inhibition of DNA replication in BALB/c 3T3 cells, but has only a small effect in P6 cells. Caffeine at a concentration of 1 mM, on the other hand, removes over 60% of the inhibition in both cell lines. The results implicate IGF-IR in the regulation of DNA replication in irradiated cells, but also suggest differences between cells of different origins in the proteins involved in the regulating signal transduction pathway.     

Xenopus Dab2 is required for embryonic angiogenesis

Background  

The molecular mechanisms governing the formation of the embryonic vascular system remain poorly understood. Here, we show that Disabled-2 (Dab2), a cytosolic adaptor protein, has a pivotal role in the blood vessel formation in Xenopus early embryogenesis.     

Seven cases of Diphyllobothrium latum infection

Seven cases of Diphyllobothrium latum infection were proved by collection of worms after praziquantel treatment between October, 1986 and July, 1987. The patients were all males aged 20-44 years residing in Seoul or Ulungdo, Kyungpook Province. All of them had the history of eating several kinds of raw marine fishes, and they had never been to abroad. One of them experienced abdominal pain and 6 experienced natural discharge of a chain of worm segments, but none revealed any sign of anemia. Total 12 worms (1-3/patient) were collected after praziquantel treatment. The worms were 85-423 cm in length, and revealed the characteristic rosette-shape uterus in their gravid proglottides. The average egg size varied 61.0-65.3 x 41.7-46.1 microns. The eggs were yellowish-brown, and ovoid to elliptical. Including the present 7 cases, the total number of human D. latum infections proven by worms in Korea becomes 28 cases.     

Enzyme polymorphism in Mansonia uniformis, a mosquito vector of brugian filariasis

Three temporal samples of a wild population of Mansonia uniformis were analysed for genetic variation at six gene-enzyme systems. Adenylate kinase, hexokinase (3 loci) and cathodal malate dehydrogenase were monomorphic. Phosphoglucomutase, glucose phosphate isomerase, isocitrate dehydrogenase and anodal malate dehydrogenase were polymorphic. Each of the polymorphic loci was represented by three alleles. The average heterozygosity or gene diversity was 0.0437.     

Influence of the<Emphasis Type="Italic">SMT2</Emphasis> knock-out on hypocotyl elongation in<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Inhibitors are very important in the study of hormone function. Brasinazole (Brz) is a specific inhibitor of brassinosteroids (BRs) biosynthesis. To expand our knowledge of the molecular mechanisms of plant steroid signaling, we performed genetic screening using medium containing Brz under dark conditions. Mutants insensitive to Brz developlonger hypocotyls than their wild type counterparts. We isolatedabz453 as a Brz insensitive mutant. TAIL-PCR and the segregation ratio of T2 plants indicated a single T-DNA insertion at the 24-Sterol C-methyltransferase (SMT2) gene in theabz453 mutant. Recapitulation for putative FCP serine phosphatase (FSP), the gene neighboringSMT2, indicated no significant phenotypes, but theSMT2 anti-sense (SMT2-AS) line developed longer hypocotyls than the wild type in medium containing Brz. Additionally, theSMT2-AS line displayed similar phenotypes to theabz453 line in soil including enhanced growth and smaller silique. Theabz453 andSMT2-AS mutants showed phenotypes similar to those of wild type in medium containing benzylaminopurine, pacrobutrazol and ACC (precursor for ethylene) under dark conditions. However, when brassinolide (BL) dose response was observed, theabz453 andSMT2-AS lines showed higher sensitivity than wild type. Theabz453/det2 andabz453/bri1-119 double mutants showed enhanced growth compared to thedet2 andbri1-119 line under both dark and light conditions. Specially, in dark conditions double mutants displayed nearly 2- and 1.5-fold longer hypocotyls thandet2 andbri1-119 plants. Brz insensitivity to theSMT2 knock-out mutant and phenotypes of double mutants indicate that not only do BRI1 and DET2 influence the BRs response, as evidenced by hypocotyl elongation, but another sterol derived signals may also be affected in mutants, suggesting that another pathway is involved in hypocotyl elongation due to SMT2.