RESPONSIVENESS OF YEAST CELLS TO AUXIN, ANIMAL SEX HORMONES AND YEAST SEXUAL HORMONES IN RELATION TO SEX CONTROLLING GENES

Genetic control of the ability of yeast cells to respond to cell-expanding action of animal, plant and yeast hormones was studied. Mating type specificity in the ability to respond to yeast sexual hormones was changed by introduction of homothallism-controlling genes, D and HM. Auxin, a plant hormone can expand cells of most homothallic strains, but not those of heterothallic strains as far as tested. Animal sex hormones showed the action similar to that of yeast sexual hormones.     

Preliminary characterization and biological reduction of putative biogenic iron oxides (BIOS) from the Tonga-Kermadec Arc, southwest Pacific Ocean

Sediment samples were obtained from areas of diffuse hydrothermal venting along the seabed in the Tonga sector of the Tonga‐Kermadec Arc, southwest Pacific Ocean. Sediments from Volcano 1 and Volcano 19 were analyzed by X‐ray diffraction (XRD) and found to be composed primarily of the iron oxyhydroxide mineral, two‐line ferrihydrite. XRD also suggested the possible presence of minor amounts of more ordered iron (hydr)oxides (including six‐line ferrihydrite, goethite/lepidocrocite and magnetite) in the biogenic iron oxides (BIOS) from Volcano 1; however, Mössbauer spectroscopy failed to detect any mineral phases more crystalline than two‐line ferrihydrite. The minerals were precipitated on the surfaces of abundant filamentous microbial structures. Morphologically, some of these structures were similar in appearance to the known iron‐oxidizing genus Mariprofundus spp., suggesting that the sediments are composed of biogenic iron oxides. At Volcano 19, an areally extensive, active vent field, the microbial cells appeared to be responsible for the formation of cohesive chimney‐like structures of iron oxyhydroxide, 2–3 m in height, whereas at Volcano 1, an older vent field, no chimney‐like structures were apparent. Iron reduction of the sediment material (i.e. BIOS) by Shewanella putrefaciens CN32 was measured, in vitro, as the ratio of [total Fe(II)]:[total Fe]. From this parameter, reduction rates were calculated for Volcano 1 BIOS (0.0521 day^?1), Volcano 19 BIOS (0.0473 day^?1), and hydrous ferric oxide, a synthetic two‐line ferrihydrite (0.0224 day^?1). Sediments from both BIOS sites were more easily reduced than synthetic ferrihydrite, which suggests that the decrease in effective surface area of the minerals within the sediments (due to the presence of the organic component) does not inhibit subsequent microbial reduction. These results indicate that natural, marine BIOS are easily reduced in the presence of dissimilatory iron‐reducing bacteria, and that the use of common synthetic iron minerals to model their reduction may lead to a significant underestimation of their biological reactivity.     

Isolation and characterization of polymorphic microsatellite DNA markers in the Japanese eight‐barbel loach,Lefua echigonia

We isolated and characterized 17 polymorphic microsatellite loci for the Japanese eight‐barbel loach, Lefua echigonia, an endangered freshwater species in streams including agricultural canals in Japan. The number of observed alleles for each locus ranged from two to nine, and the values of observed and expected heterozygosities ranged from 0.125 to 0.844 and from 0.148 to 0.876, respectively. All loci conformed to Hardy–Weinberg equilibrium. Genetic linkage disequilibrium analysis between all pairs of the loci showed no significant departure from the null hypothesis between any of the loci.     

Release of a Gonad-Stimulating Substance from the Radial Nerves of the Cushion Star,Asterina pectinifera,in response to Excess Potassium*

The release of a gonad-stimulating substance (GSS) from radial nerves stimulated by a K⁺-rich solution was examined in the cushion star, Asterina pectinifera. The threshold concentration of K⁺necessary for the release of a sufficient amount of GSS to induce shedding of mature oocytes from ovarian fragments was 50 to 75 mM. The minimal amount of fresh nerve required for this release was 3 mg per ml of medium. The time of K⁺stimulation necessary to induce maximal GSS release was about 20 min. Repeated stimulations of radial nerves with 100 mM K⁺caused repeated release of GSS.     

Water potential, turgor and cell wall properties in elongating tissues of the hydrotropically bending roots of pea (Pisum sativum L.)

The hydrotropic bending of roots of an ageotropic pea mutant, ageotropum, was studied in humid air in a chamber with a steady humidity gradient. We examined the effects of atmospheric humidity around the root on the water status of root tissues, as well as the wall growth and the hydraulic properties of the elongating tissues. Atmospheric humidity at the surface of the root was clearly lower on the side orientated towards the air with lower humidity than on the side orientated towards the air with higher humidity. However, there were no differences in water potential and osmotic potential between the tissues that faced air with higher and lower humidities in the elongating and mature regions. Plastic extensibility was higher in the tissues that faced the air with lower humidity than in the tissues that faced the air with higher humidity. No differences in turgor pressure and yield threshold were observed between the tissues that faced air with higher and lower humidities. Therefore, the extensibility of the cell wall appeared to be responsible for the different growth rates of tissues in root hydrotropism. A further probable cause of the hydrotropical bending of roots is changes in the hydraulic conductance in the elongating tissues. Since the hydrotropic bending of roots occurred only when a root tip was exposed to a humidity gradient, hydrotropism might occur after perception of a difference in humidity by the root tip, with accompanying changes in cell wall extensibility and hydraulic conductance.     

Phenotypic plasticity of internode elongation stimulated by deep-seeding and ethylene in wheat seedlings

Deep-seeding and ethylene were found to stimulate extension growth of the first internode of intact wheat (Triticum aestivum L.) seedlings in darkness. Seedlings of Hon Mang Mai emerged from much deeper in the soil than the seedlings of the other varieties used and their first internodes elongated to a much greater extent in response to ethylene. Carbon dioxide slowed elongation of the first internode and inhibited ethylene action. Elongation of the first internode due to deep-seeding and ethylene treatment showed high heritabilities, suggesting a genetic basis underlying those traits.     

Relationship between Floret Elongation and Pigment Synthesis in the Flowers of Carthamus tinctorius

Floret elongation and levels of precarthamin were investigatedin freshly collected flowers of Carthamus tinctorius. Accumulationof precarthamin was found to be induced at the early stagesof floret elongation. [U-¹⁴C]Acetate and [U-¹⁴C]phenylalaninewere incorporated into precarthamin in the detached floretsfrom the flower bud. The results suggest that precarthamin issynthesized via the acetate-shikimate pathway. Carthamus tinctorius L, floret elongation, pigment synthesis, precarthamin     

CHANGES IN THE MELANOPHOROTROPIC FUNCTION OF THE PITUITARY GLAND ACCOMPANYING BLINDNESS IN XENOPUS LAEVIS DAUDIN

A number of cases of blindness appeared among a group of cultured Xenopus laevis. The blind toads lacked eyeballs and optic nerves and were consistently dark in color. Similar anatomical changes in the head and pigmentation were produced experimentally by removing the eyeballs of tadpoles or young adult toads. The dark pigmentation of blind Xenopus: was shown to be due to the continuous release of MSH from the pars intermedia of the pituitary, since hypophysectomy led to the complete blanching of the dermal and epidermal melanophores. MSH activity in the pars intermedia of blind toads was extremely high in comparison with that of normal animals. No special difference with respect to the general growth and behaviour was found between normal and blind Xenopus, which suggests that the pituitary functions other than that of the pars intermedia are not affected by the state of the optic nerves. These observations suggest that the retrogressive degeneration of the optic nerves exerts a profound effect on the secretory activity of the pars intermedia via the hypothalamic controlling center.     

Changes of Starch Synthetase Activity of Cucumber Leaves during Ammonium Toxicity

The changes of granule bound starch synthetase activity in cucumber leaves (Cucumis sativus L. cv. Suisei No. 2) were investigated during ammonium toxicity. Generally speaking the quantity of starch granules of injured plants were less than that of normal plants. ADPG is a more effective glucose donor to starch synthesis than UDPG. It was found that the starch synthetase activity of injured plants was decreased compared to the normal plants. This variation of enzyme activity was higher when UDPG was used as glucose donor. The addition of K⁺ and NH₄⁺ generally inhibited the enzyme activity when UDPG was used as glucose donor, but stimulated it when ADPG was used. This stimulation was found to be more effective in enzymes prepared from injured plants than from normal plants. The level of potassium bound to starch granules was not changed markedly between normal and injured plants.     

Freeze-Fracture Study of the Bloodstream Form of Trypanosoma brucei gambiense

The ultrastructure of Trypanosoma brucei gambiense was investigated by the freeze-fracture method. Three different regions of the continuous plasma membrane; cell body proper, flagellar pocket, and flagellum were compared in density and distribution of the intramembranous particles (IMP's). The IMP-density was highest in the flagellar pocket membrane and lowest in flagellum. Intra membranous particles of the cell body membrane were distributed uniformly on both the protoplasmic (P) and exoplasmic (E) faces. On the P face of the flagellar membrane, a single row of IMP-clusters was seen along the juncture of the flagllum to the cell body. Since the spacing of the IMP-clusters was almost equal to the spacing of the paired rivet structures observed in thin section, these clusters likely are related to the junction of flagellum and cell body. At the neck of the flagellar pocket, several linear arrays of IMP's were found on the P face of the flagellar membrane, while on the E face rows of depressions were seen. At the flagellar base, the clusters of IMP's were only seen on the P face. On the flagellar pocket membrane, particle-rich depressions and linear particle arrays were also found on the P face, while on the E face such special particle arrangements were not recognized. These particle-rich depressions may correspond to the sites of pinocytosis of the bloodstream forms which have been demonstrated in thin sections.