Genotype-environment interaction for awn development in isogenic lines of barley

Summary Awn length of four isogenic lines of barley differing by two genes for awn development (A andB) and their short iinkage blocks was evaluated at a wide range of plant densities (0.002 to 3.345 m²/plant) for two years. Awn development was reduced at high plant density. The quarter-awned genotype (aaBB) became phenotypically awnless (aabb) at high plant density. Similar results were obtained each year and the genotype x plant density effect was the major portion of the genotype-environment interaction variance. Additive ( _A , _B ) and additive x additive ( _AB ) gene effects were computed for each plant density for lateral and central floret awn length. For lateral awns _AB was not affected, but _A and _B increased with decreased plant density. In contrast, for central awns _A and _AB decreased and _B increased with decreased plant density.Central floret awns measured at each spike node showed that high plant density reduced awn development most in the lower half of the spike. This is the zone of most rapid awn differentiation and since culm elongation and spike growth rates were greatly increased by high plant density, it was suggested that rapid growth invoked a stress on awn development and differentially altered the expression ofA andB.

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Zusammenfassung An 4 isogenen Gerstenlinien, die sich durch zwei Gene für Grannenbildung (A undB) und entsprechende kurze Kopplungsblocks unterscheiden, wurde zwei Jahre lang die Länge der Grannen bei verschiedener Standdichte (0,002 bis 3,345 m² je Pflanze) untersucht. Bei dichtem Bestand ergab sich eine Beeinträchtigung der Grannenbildung, der viertelbegrannte Genotyp (aaBB) wurde phänotypisch grannenlos (aabb). Die Ergebnisse stimmten in beiden Jahren überein, der Effekt Genotyp x Standdichte hatte den Hauptanteil an der Interaktionsvarianz Genotyp: Umwelt. Additive ( _A , _B ) und additive x additive ( _AB ) Genwirkungen wurden bei jeder Standdichte für die Grannenlänge der Seiten-und Mittelährchen errechnet. Bei den seitlichen Grannen wurde _AB nicht beeinflußt, aber _A und _B erhöhten sich mit abnehmender Standdichte. Im Gegensatz dazu gingen bei den mittleren Grannen _A und _AB zurück, während für _B bei abnehmender Standdichte ein Ansteigen festzustellen war.Messungen der mittleren Grannen jeder Ähre zeigten, daß hohe standdichte der Pflanzen die Grannenbildung am meisten in der unteren Hälfte der Ähre reduzierte. Das ist die Zone, in der sich die Grannen am schnellsten differenzieren, und da die Halm- und Ährenwachstumsraten durch hohe Standdichte stark gesteigert wurden, scheint das schnelle Wachstum auf die Grannenentwicklung hemmend einzuwirken und die Manifestierung vonA undB unterschiedlich abzuändern.

     

Lifetime of bacterial messenger ribonucleic acid

Moses, V. (University of California, Berkeley), and M. Calvin. Lifetime of bacterial messenger ribonucleic acid. J. Bacteriol. 90:1205-1217. 1965.-When cells from a stationary culture of Escherichia coli were placed in fresh medium containing inducer for beta-galactosidase, growth, as represented by increase in turbidity and by total protein synthesis, started within 30 sec. By contrast, beta-galactosidase synthesis was greatly delayed compared with induction during exponential growth. Two other inducible enzymes (d-serine deaminase and l-tryptophanase) and one repressible enzyme (alkaline phosphatase) showed similar lags. The lags were not due to catabolite repression. They could not be reduced by pretreatment of the culture with inducer, or by supplementing the fresh medium with amino acids or nucleotides. The lag was also demonstrated by an i(-) mutant constitutive for beta-galactosidase synthesis. An inhibitor of ribonucleic acid (RNA) synthesis, 6-azauracil, preferentially inhibited beta-galactosidase synthesis compared with growth in both inducible and constitutive strains. Puromycin, an inhibitor of protein synthesis, acted as an inhibitor at additional sites during the induction of beta-galactosidase synthesis. No inhibition of the reactions proceeding during the first 20 sec of induction was observed, but puromycin seemed to prevent the accumulation of messenger RNA during the period between 20 sec and the first appearance of enzyme activity after 3 min. It is suggested that these observations, together with many reports in the literature that inducible enzyme synthesis is more sensitive than total growth to some inhibitors and adverse growth conditions, can be explained by supposing that messenger RNA for normally inducible enzymes is biologically more labile than that for some normally constitutive proteins. The possible implications of this hypothesis for the achievement of cell differentiation by genetic regulation of enzyme synthesis are briefly discussed.     

SALT TOLERANCE WITHIN A TYPHA POPULATION

Mc Millan , Calvin . (U. Texas, Austin.) Salt tolerance within a Typha population. Amer. Jour. Bot. 46(7): 521–526. Illus. 1959.—Typha in a disturbed salt flat near Lincoln, Nebraska, provided material for an examination of population dynamics. Within the population, clones of T. angustifolia L. tended to occupy the drier sites and those of T. latifolia L. occupied the sites of greater moisture probability. Clones of intermediate morphological characteristics were distributed with both T. angustifolia and T. latifolia. Rhizomes taken from the clones were grown in various NaCl solutions in the greenhouse. Results indicated greatest salt tolerance by T. angustifolia and least salt tolerance by T. latifolia. The intermediate, probably hybrid, clones were intermediate in salt tolerance. Seeds of the 3 clone-types germinated over the same range of salt concentration. The seeds of all 3 types withstood 4 months submergence in a 2% salt solution and germinated upon being returned to tap water. In the salt flat habitat, the clones of T. latifolia were not vigorous during the years 1956–1957 and many died or were reduced considerably in area of occupancy. The clones of T. angustifolia remained vigorous and flowered over the same period. The intermediate clones were vigorous and increased their coverage, primarily in areas that were occupied prior to 1956 by T. latifolia. The spatial adjustments within the population probably resulted from the selective action of increased salt concentration accompanying the drier conditions of 1956 and 1957.     

Microtubule assembly is required for the formation of the pronuclei,nuclear lamin acquisition,and DNA synthesis during mouse,but not sea urchin,fertillization

Microtubule assembly is required for the formation of the male and female pronuclei during mouse, but not sea urchin, fertilization. In mouse oocytes, 50 μM colcemid prevents the decondensation of the maternal meiotic chromosomes and of the incorporated sperm nucleus during in vitro fertilization. Nuclear lamins do not associate with either of the parental chromatin sets although peripherin, the PI nuclear peripheral antigen, appears on both. DN A synthesis docs not occur in these fertilized, colcemid-arrested oocytes. This effect is limited to the first hours after ovulation, since colcemid added 4–6 hours later no longer prevents pronuclear development, lamin acquisition, or DNA synthesis. Neither microtubule stabilization with 10 μM taxol nor microfilament inhibition with 10 μM cytochalasin D or 2.2 μg/ml lalrunculin A prevent these pronuclear events; these drugs will inhibit the apposition of the pronuclei at the egg center. In sea urchin eggs, colcemid or griseofulvin treatment doe? not result in the same effect and the male pronucleus forms with the attendant accumulation of the nuclear lamins. The differences in the requirement for microtubule assembly during pronucleus formation may be related to the cell cycle: In mice the sperm enters a meiotic cytoplasm, whereas in sea urchin eggs it enters an interphase cytoplasm. Refertilization of mitotic sea urchin eggs was performed to test the possibility that this phenomenon is related to whether the sperm enters a meiotic/mitotic cytoplasm or one at interphase; during refertilization at first mitosis, the incorporated sperm nucleus is unable to decondense and acquire lamins. These results indicate a requirement for microtubule assembly for the progression from meiosis to first interphase during mouse fertilization and suggest that the cytoskeleton is required for changes in nuclear architecture necessary during fertilization and the cell cycle.     

Cloning and Expression of a 5-Hydroxytryptamine7 Receptor Positively Coupled to Adenylyl Cyclase

Abstract: In a number of different cell types, phosphorylation of a 63-kDa protein has been shown to increase rapidly in response to stimuli that lead to an increase in intracellular calcium. Here, a stimulus-sensitive protein at this molecular weight is identified in PC12 cells and rat cortical synaptosomes as phosphoglucomutase. In addition, the added phosphate is shown to be in an oligosaccharide terminating in phosphodiester-linked glucose. In synaptosomes, incorporated radioactivity, following incubation with [¹⁴C]glucose or the [β-³⁵S]phosphorothioate analogue of UDP-glucose, was found to increase within 5 s of stimulation and return to baseline within 25 s. Despite the many pathways utilizing glucose, this was the only detectable protein glycosylation observed in synaptosomes. These results indicate that cytoplasmic glycosylation is reversible and rapidly regulated, and suggest that phosphoglucomutase undergoes an alteration in function and/or topography in response to increases in intracellular calcium.     

Aggregation and the maintenance of genetic diversity: An individual-based cellular model

Summary A cellular model, where each individual is explicitly defined, is used to describe a population of a mycophagous species ofDrosophila. Patches represent single fungal fruiting bodies which are only available as oviposition sites for a single fly generation. Standard competition equations are used to describe the interaction between larval genotypes at each patch. Dispersal of adults is obligatory and uses a simple model of patch choice to produce aggregated arrivals of adults at fresh patches. The degree to which aggregation of adults and eggs can promote coexistence of genotypes in a one-locus, two-allele system with dominance is explored. When both phenotypes (A- andaa) are aggregated, a polymorphism can be maintained for over 1000 generations even when the selective disadvantage of one phenotype (aa) is great. This model enhances the degree of polymorphism in a population, using aggregation. It does not preclude the operation of other methods which enhance the coexistence of genotypes. Therefore, it is acting to augment the degree of polymorphism maintained in species which exploit patchy and ephemeral habitats, including allDrosophila and a wide range of other organisms.     

Effects of estradiol-17β in the male xenopus laevis: Isolation and translation of cytoplasmic messenger rna populations

Summary Total Xenopus liver cytoplasmic RNA isolated following long-term estrogen administration (14 days) was fractioned using Sepharose 4B chromatography. One of the Sepharose 4B peaks was shown to contain RNA with a molecular weight reported for vitellogenin mRNA (34S). The presence of estrogeninduced vitellogenin mRNA in the peak 5 RNA was determined by translation of the RNA in the oocyte and analysis of the oocyte translational products by immunoprecipitation with anti-vitellogenin.Sepharose 4B peaks 2 and 3 were also observed to contain estrogen induced mRNA populations sedimenting between 9-18S. These findings suggest that Sepharose 4B chromatography might prove useful in separating different mRNA populations following estrogen-induced gene activation.     

Flow field-flow fractionation as a methodology for protein separation and characterization

Flow field-flow fractionation is introduced as a new tool applicable to protein studies. Specific advantages of this method are discussed, including the capability for measuring diffusivities and Stokes radii directly, even for trace components. The theoretical equations of flow FFF are summarized and expanded to include an explicit dependence on the Stokes radius. Several native proteins are retained. The retention is shown to be systematically controllable by changes in cross flow and the results are in quantitative agreement with theory. Fractograms of different rat plasmas are then shown to produce coincident peaks, while human plasma exhibits several systematic peak shifts with respect to the fractogram of the rat plasma. Finally, changes in the Stokes radii of ferritin peaks are shown after various forms of treatment with SDS. Flow FFF in this study demonstrates a capability of working with a mass range of ∼ 10⁵ in a single run.