Efficient production of wheat-barley hybrids and preferential elimination of barley chromosomes

Summary Intergeneric hybridization between four common wheat cultivars, Triticum aestivum L. cultivars Chinese Spring, Norin 12, Norin 61, and Shinchunaga, and cultivated barley, Hordeum vulgare L. cultivars Betzes, Nyugoruden, Harunanijou, and Kinai 5 were carried out in a greenhouse under 15 – 20 °C and long-day (15 h) photoperiod conditions. Two days prior to pollination, a 100 mg/1 2,4-D solution was injected into wheat stems. Among wheat cultivars, Norin 12, Norin 61, and Shinchunaga showed higher crossabilities than that of Chinese Spring, suggesting the presence of crossability gene(s) other than the kr system of Chinese Spring. Variation was also found among the barley cultivars as male parents. Betzes barley showed the highest crossability with wheat. Thus, the cross Norin 12×Betzes showed the highest crossability (8.25%), followed by Norin 61 ×Betzes (6.04%), Shinchunaga×Betzes (5.00%), and Shinchunaga×Kinai 5 (5.00%). The embryos were rescued by culture at 15–20 days after pollination. Seventyfour plants were obtained from 82 embryos. The morphology of the hybrid plants resembled that of wheat parents. Among 60 seedlings observed, 28 had 28 chromosomes, 8 had 21, 23 had aneuploid numbers of chromosomes (22–27), and 1 had 29 chromosomes. About half of the aneuploid hybrids showed mosaicism for chromosome number. By analyzing five isozyme markers of barley chromosomes, the chromosome constitutions of the aneuploid hybrids were determined. Barley chromosomes 1 and 5 were found to be preferentially eliminated in the hybrids, while chromosomes 2 and 4 were eliminated infrequently. The conditions and genetic factors for high crossability and the tendency of barley chromosome elimination are discussed.     

Silence of streptomycin 6-phosphotransferase gene derived by incubation at a high temperature inStreptomyces griseus

Summary The bald mutants from streptomycin (SM)-producingStreptomyces griseus 2247 obtained by incubation at high temperature (36° C), designated as HT strains, lost resistance to their own antibiotic and scarcely produced the antibiotic. Although SM susceptibility in the mutant was due to loss of SM 6-phosphotransferase activity produced in the cell, the gene coding for the enzyme cloned from an HT strain was surely expressed inS. lividans 1326 as a host. Northern blot analysis showed that the corresponding RNA is not detected in the mutant, indicating that though the gene encoding SM 6-phosphotransferase, at least, the structural gene is not deleted in the cell, the expression is silent.     

Porcine brain natriuretic peptide-like immunoreactivity in rat tissues

The presence of immunoreactive porcine brain natriuretic peptide in rat tissues was studied with a specific radioimmunoassay for porcine brain natriuretic peptide-26. The cross-reactivity of the antiserum used was less than 0.001% with rat atrial natriuretic peptide, rat brain natriuretic peptide-32 and rat brain natriuretic peptide-45. Immunoreactive porcine brain natriuretic peptide was detectable in various tissues of the rat, and high concentrations of immunoreactive porcine brain natriuretic peptide were found in the brain and cardiac atrium, with the highest level in the hypothalamus (159±30 fmol/gram wet tissue, mean±SEM, n=4). Reverse phase high performance liquid chromatography showed that the immunoreactive porcine brain natriuretic peptide of the whole brain and heart extracts eluted mainly at an identical position to synthetic porcine brain natriuretic peptide-26. These findings indicate that porcine brain natriuretic peptide-like substance, distinct from rat brain natriuretic peptide, is present in high concentrations in the rat brain and cardiac atrium.     

Molecular cloning of complementary DNA encoding one of the human pancreatic protease E isozymes

We have cloned a DNA from a human pancreatic cDNA library using a cloned rat pancreatic elastase 1 cDNA as a probe, and determined its nucleotide sequence. This cDNA contains a coding region of 810 nucleotides which encodes a 270-amino-acid protein. The deduced amino acid sequence shows less than 60% homologies with rat and porcine pancreatic elastase 1, although its substrate binding region is homologous with those of the above elastases 1. When this deduced amino acid sequence was compared with known amino acid sequences of pancreatic proteases other than elastases, it was found to contain an amino acid sequence which was highly homologous with the N-terminal amino acid sequence of porcine pancreatic protease E. We also purified human pancreatic protease E isozymes from human pancreatic juice, and determined their N-terminal amino acid sequences. One of the isozymes does not hydrolyze elastin but does hydrolyze a synthetic substrate. Endoglycosidase F digests glycoside bonds of the isozyme. These results suggest that the cDNA cloned by us corresponded to one of the human protease E isozymes.     

Thioridazine enhances lysosomal accumulation of epidermal growth factor and toxicity of conjugates of epidermal growth factor with Pseudomonas exotoxin

Thioridazine, a phenothiazine calmodulin inhibitor, aggravated the cytotoxic effect of a conjugate (EGF-PE) of epidermal growth factor (EGF) coupled with Pseudomonas exotoxin against cultured HeLa cells. Other phenothiazine calmodulin inhibitors, trifluoperazine and chlorpromazine, also intensified the cytotoxic effect of EGF-PE, whereas N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W7) had no such effect. By using iodinated epidermal growth factor ( [125I]EGF), the effect of thioridazine on intracellular transport of EGF was examined. The release of radioactivity associated with [125I]EGF into medium was slow in the presence of thioridazine. The Percoll gradient centrifugation pattern showed that thioridazine delayed both the appearance of [125I]EGF in lysosomes and the disappearance of [125I]EGF from the lysosomes. The pH value in lysosomes was 5.28 in thioridazine-treated HeLa cells, while that in untreated cells was 5.15. Thioridazine was found to inhibit lysosomal enzyme activities of cathepsin B and acid phosphatase, but not beta-hexosaminidase when cell extracts were treated with the drug. Electron microscopy showed an increased number of electron-dense bodies, possibly autophagosomes/lysosomes in HeLa cells grown for 48 h with 3 micrograms/ml thioridazine. The potentiating action of EGF-PE by thioridazine is discussed in relation to the altered lysosomal function in treated cells.     

Characterization of human genomic DNA sequences homologous to the interleukin 2 cDNA

Southern blot analysis of human placental DNA under low stringency hybridization conditions revealed several DNA fragments hybridizable to the human interleukin 2 (IL-2) cDNA. Four phage clones carrying these IL-2 cDNA-like sequences were isolated and their structures analyzed. A DNA fragment derived from one of the clones gave the strongest hybridization signal. Sequence analysis of this fragment revealed the presence of a cluster of three DNA segments, i.e. 20 base pairs (bp), 57 bp and 18 bp in length and having about 85%, 80% and 83% homology to three different parts of the coding region of human IL-2 cDNA, respectively.     

Simulation analysis of excitation conduction in the heart: Propagation of excitation in different tissues

The normal excitation and conduction in the heart are maintained by the coordination between the dynamics of ionic conductance of each cell and the electrical coupling between cells. To examine functional roles of these two factors, we proposed a spatially-discrete model of conduction of excitation in which the individual cells were assumed isopotential. This approximation was reasoned by comparing the apparent space constant with the measured junctional resistance between myocardial cells. We used the four reconstruction models previously reported for five kinds of myocardial cells. Coupling coefficients between adjacent cells were determined quantitatively from the apparent space constants. We first investigated to what extent the pacemaker activity of the sinoatrial node depends on the number and the coupling coefficient of its cells, by using a one-dimensional model system composed of the sinoatrial node cells and the atrial cells. Extensive computer simulation revealed the following two conditions for the pacemaker activity of the sinoatrial node. The number of the sinoatrial node cells and their coupling coefficients must be large enough to provide the atrium with the sufficient electric current flow. The number of the sinoatrial node cells must be large so that the period of the compound system is close to the intrinsic period of the sinoatrial node cell. In this simulation the same sinoatrial node cells produced action potentials of different shapes depending on where they were located in the sinoatrial node. Therefore it seems premature to classify the myocardial cells only from their waveforms obtained by electrical recordings in the compound tissue. Second, we investigated the very slow conduction in the atrioventricular node compared to, for example, the ventricle. This was assumed to be due to the inherent property of the membrane dynamics of the atrioventricular node cell, or to the small value of the coupling coefficient (weak intercellular coupling), or to the electrical load imposed on the atrioventricular node by the Purkinje fibers, because the relatively small atrioventricular node must provide the Purkinje fibers with sufficient electric current flow. Relative contributions of these three factors to the slow conduction were evaluated using the model system composed of only the atrioventricular cells or that composed of the atrioventricular and Purkinje cells. We found that the weak coupling has the strongest effect. In the model system composed of the atrioventricular cells, the propagation failure was not observed even for very small values of the coupling coefficient.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ferricyanide Induces Flowering by Suppression of Nitrate Assimilation in Lemna paucicostata 6746

Lemna paucicostata 6746, a short-day plant, produced flowerbuds even under continuous light when cultured for 3 days inferricyanide containing ammonium-free medium followed by cultureon nitrogen-rich medium (either nitrate or ammonium). Dailytreatment with ferricyanide in the absence of ammonium for morethan 8 hours, which completely inhibited nitrate reductase activitywithin 6 hours after the addition to the medium, induced daylength-independentflowering even when the ammonium-rich medium was given duringthe remaining hours. The presence of ammonium for 1 hour atthe middle of the 14-h ferricyanide treatment almost completelysuppressed floral induction. (Received March 6, 1986; Accepted June 3, 1986)     

Inhibition of Flowering in the Long-Day Plant Lemna gibba G3 by Hutner's Medium and its Reversal by Medium Modification

The long-day plant Lemna gibba G3 flowers normally in E medium(Hoagland-type medium plus 30 µM EDTA) but in 0.5 H mediumthere is no flowering. Ammonium is present in 0.5 H medium andis known to inhibit flowering in L. gibba G3, but even in NH₄⁺-free0.5 H medium there is virtually no flowering under continuouslight. Increasing the phosphate concentration of the NH₄⁺-free0.5 H medium from 1.15 ITIM to 12 or 16 mM results in substantialflowering. Decreasing the EDTA concentration from 850 µIMto 250 µM, or raising the nitrate concentration from 4mM to 12 mM, results in only a small increase in flowering.If the decrease in EDTA and increase in nitrate are combinedwith the increase in phosphate, however, the flowering responseis nearly as good as that obtained using E medium. Thus, withthese three changes the inhibitory effect of NH₄⁺free 0.5 Hmedium for flowering in L. gibba G3 is almost completely reversed In the above studies flowering was not limited by daylength.When plants were grown on E medium under an 11 hour daylengthwhere flowering is limited by daylength, decreasing the phosphateconcentration in the medium reduced flowering, but increasingthe phosphate concentration in the medium did not stimulateflowering. Thus, when flowering is limited by daylength, highphosphate will not cause flowering, but a certain level of phosphateappears to be necessary for the expression of photoinductionunder long days. (Received January 14, 1986; Accepted June 24, 1986)