Photoactivation of the latent water-oxidizing complex in photosystem II membranes isolated from dark-grown spruce seedlings

Photosystem II membranes (D-PSII) were isolated from dark-grown spruce seedlings. All major PSII proteins except the 17- and 23-kDa extrinsic proteins were present in D-PSII. O₂ evolution and Mn content in D-PSII were negligible, while PSII-donor activity showed a value comparable to that of NH₂OH-treated PSII membranes (NH₂OH-L-PSII) from light-grown seedlings. Light incubation of D-PSII with 1 m M MnCl₂, 50 m M CaCl₂ and 100 μ M DCIP at pH 5.3 resulted in activation of the latent water-oxidizing complex. Accomplishment of photoactivation of PSII membranes from dark-grown spruce seedlings clearly indicates that only ligation of Mn²⁺ to the apo-water oxidizing complex is required for expression of O₂ evolution, and that protein synthesis is not involved in the photoactivation process. There was no essential difference between 'photoactivation' of naturally Mn-free PSII membranes and 'photoreactivation' of artificially Mn-depleted PSII membranes on kinetics, pH dependence, Mn²⁺-concentration dependence. However, kinetics and pH dependence of photoactivation were appreciably different in spruce PSII membranes and in PSII membranes of angiosperms such as wheat and spinach.     

Molecular analysis of esterase D polymorphism

We have analyzed the esterase D (EsD) polymorphism at the nucleic acid level. Two common alleles, EsD¹ and EsD², are characterized by the substitution of one amino acid (Gly-to-Glu), which is caused by the point mutation of one nucleotide (G-to-A). Individuals exhibiting the EsD1 and EsD 2 phenotypes are homozygotes for EsD 1 and EsD 2 cDNAs, respectively. Individuals showing the EsD 2-1 phenotype have two kinds of cDNAs, viz., EsD 1 and EsD 2. The point mutation difference between the cDNAs of the EsD¹ and EsD² alleles results in a different SspI digestion site. A restriction fragment length polymorphism caused by this difference with respect to the SspI digestion site makes it possible to determine the EsD phenotype using DNA samples extracted from forensic materials with no EsD enzymatic activity.     

Seasonal change in the food habits of the Iriomote catFelis iriomotensis

The food habits of the Iriomote catFelis iriomotensis were studied by analyzing 177 feces collected monthly from 1987 to 1988. A total of 26 food items were identified. The frequency of lizards and frogs in the feces was higher than those of mammals and birds. The food habits changed greatly seasonally.Eumeces skinks were fed on most frequently, and found in the feces with a similar high frequency occurrence in March–April and July–September, while their proportion to the total number of food items was larger in March–April than in July–September. The cats fed on larg-sized skinks, adultEumeces kishinouyei, more in March–April than in other seasons. The number of skinks sighted in the course of a road census was greater from March to August, and large-sized skinks were sighted more in March–April than in July–August. The cats fed selectively on large-sized skinks in every season. Therefore, changes in the food habits depended on the food availability. Characteristics of food habits in the Iriomote cat are discussed in comparison with the food habits of other felids in temperate and tropical regions.     

Isolation of a new cDNA clone encoding an Rh polypeptide associated with the Rh blood group system

We searched for a human chromosome that would restore the cholesterol metabolism in 3T3 cell lines (SPM-3T3) derived from homozygous sphingomyelinosis mice (spm/spm). Mouse A9 cells containing a single copy of pSV2neo-tagged chromosomes 9, 11, or 18 derived from normal human fibroblasts served as donor cells for transfer of human chromosomes. Purified A9 microcells were fused with SPM-3T3 cells, and the microcell hybrids were selected in medium containing G418 antibiotics. The microcell hybrids that contained human chromosomes 9, 11, or 18 in a majority of cells were examined. The accumulation of intracellular cholesterol in the microcell hybrids containing a chromosome 18 decreased markedly, whereas in the microcell hybrids containing either chromosomes 9 or 11 it was similar to that in SPM3T3 cells. The SPM-3T3 cells with an intact chromosome 18 were further passaged and subcloned. Clones which again accumulated intracellular cholesterol had concurrently lost the introduced chromosome 18. The abnormal accumulation was associated with a decrement in the esterification of exogenous cholesterol. These findings suggest that the gene responsible for the abnormal cholesterol metabolism in the spm/spm mice can be restored by a hu man chromosome 18. The gene was tentatively mapped on 18pter18p11.3 or 18q21.3qter that was lost during subcloning, thereby resulting in reaccumulation of the intracellular cholesterol.     

Acidiphilium aminolytica sp. nov.: An acidophilic chemoorganotrophic bacterium isolated from acidic mineral environment

Acidiphilium aminolytica is proposed for a species of the genusAcidiphilium. Acidiphilium aminolytica can be phenotypically differentiated from all other species of the genusAcidiphilium. The seven strains of this species that have been studied are Gram-negative, aerobic, mesophilic, non-sporeforming, motile, and rod-shaped bacteria. They grow between pH 3.0 and 6.0, but not at pH 6.5. They yield positive results in tests for hippuric acid hydrolysis, catalase and urease production. Oxidase, esculin hydrolysis, and -galactosidase tests are negative. They can used-glucose,d-galactose, inositol, sorbitol,l-lysine,l-glutamate,l-arginine, -alanine,dl-4-aminobutyrate,dl-5-aminovalerate, sperimine, or diaminobutane as a sole carbon source, but cannot use elemental sulfur and ferrous iron as an energy source. The DNA base composition is 58.7–59.2 G+C mol%. The major isoprenoid quinone is ubiquinone with ten isoprene unit (Q-10). The major fatty acid is the C_18:1 fatty acid. Two ornithine amide lipids, the C_18:1 fatty acid esters of -N-3-hydroxystearylornithyltaurine and -N-3-hydroxystearylornithine, are detected as the polar aminolipid. DNA relatedness between this species and the other species ofAcidiphilium, the generaAcidomonas, andAcidobacterium was 29 to 2%. These results indicate, that this new species should be placed in the genusAcidiphilium. The type strain (strain 101) ofA. aminolytica is JCM 8796.     

Growth Characteristics and Intraspecies Host Specificity of a Large Virus Infecting the Dinoflagellate Heterocapsa circularisquama

The growth characteristics and intraspecies host specificity of Heterocapsa circularisquama virus (HcV), a large icosahedral virus specifically infecting the bivalve-killing dinoflagellate H. circularisquama, were examined. Exponentially growing host cells were more sensitive to HcV than those in the stationary phase, and host cells were more susceptible to HcV infection in the culture when a higher percent of the culture was replaced with fresh medium each day, suggesting an intimate relationship between virus sensitivity and the physiological condition of the host cells. HcV was infective over a wide range of temperatures, 15 to 30°C, and the latent period and burst size were estimated at 40 to 56 h and 1,800 to 2,440 infective particles, respectively. Transmission electron microscopy revealed that capsid formation began within 16 h postinfection, and mature virus particles appeared within 24 h postinfection at 20°C. Compared to Heterosigma akashiwo virus, HcV was more widely infectious to H. circularisquama strains that had been independently isolated in the western part of Japan, and only 5.3% of the host-virus combinations (53 host and 10 viral strains) showed resistance to viral infection. The present results are helpful in understanding the ecology of algal host-virus systems in nature.     

Isolation of cDNA for a Plasma Membrane H+-ATPase from Guard Cells of Vicia faba L.

cDNA encoding the plasma membrane H⁺-ATPase of guard cells ofVicia faba L. was isolated. The clone encoded a 105-kDa polypeptide(956 amino acids) that was 79–85% identical in terms ofamino acid sequence to other plant H⁺-ATPases. High levels ofmRNA explain the high H⁺-ATPase activity of these plasma membranes. (Received December 24, 1994; Accepted April 12, 1995)     

Numerical simulation of neuronal population coding: influences of noise and tuning width on the coding error

Performance of neuronal population coding is investigated numerically, in neurons with Gaussian tuning functions of various widths and noise ratios. The present model is applicable to both direction coding and orientation coding. It is shown that the coding error exhibits peculiar dependence on the width of the tuning function and that the dependence under the influence of noise is different from that of the noise-free case. In the absence of noise, the coding error increases monotonically with the width of the tuning function. The increment obeys the power law (the exponent estimated is 0.501) when the width is less than the critical value. In this region of the width a scaling law is obtained, which shows that the root-mean-square error is proportional to the square root of the ratio of the width of the tuning function to the population size. When the width exceeds the critical value, the coding error increases more rapidly than the power law. The reason for this anomalous increase, not seen previously, is argued. Existence of noise changes the dependence of the coding error on the width of the tuning function. Unlike the noise-free case, the error under the influence of noise becomes minimum at an intermediate value of the width. The width that gives the minimum coding error is termed the optimum width in this article. The numerical results suggest that the optimum width is roughly proportional to the square root of the noise ratio but has only a weak dependence on the population size. It is further shown that the coding error for the optimum width increases sharply when the noise ratio exceeds about 0.5 and is inversely proportional to the square root of the population size.     

Distribution of growth regulators in relation to the light-induced geotropic responsiveness in Zea roots

Growth regulators were measured in extracts from the upper and lower halves of 7-mm apical segments of horizontally oriented, red-light-irradiated and non-irradiated roots of Zea mays L. cv. Golden Cross Bantam 70 which exhibit a georesponse only after an exposure to light. Abscisic acid (ABA) was measured by gas-liquid chromatography, auxin (indole-3-acetic acid, IAA) by the Avena straight-growth assay, and an unidentified growth inhibitor by a Zea root-growth assay. The ratio of ABA in the upper and lower halves was 1.6 in the irradiated roots and 1.0 in the non-irradiated ones. The total amount of ABA after irradiation was increased by a factor of ca. 1.8. The ratio of IAA in the upper and lower halves of irradiated and non-irradiated roots was 1:3.4 and 1:2.9, respectively. The content (or activity) of an unidentified growth inhibitor was highest in the lower halves of horizontally oriented roots which had been irradiated with red light. The unidentified growth inhibitor, rather than IAA or ABA, may be the major factor in the light-induced geotropic responsiveness in Zea roots.     

Dormancy in Dioscorea: Generality of gibberellin-induced dormancy in asexual dormant organs

Effects of GA₃ and CCC application on the sprouting of bulbilsor subterranean dormant organs of 10 species in the genus Dioscoreawere observed. Although the efficiency of both chemicals differedby species, in general GA₃ inhibited and CCC promoted the sproutingof the above dormant organs. In some species, however, dilutedGA₃ (0.003–0.3 µM) has a promotive and diluted CCC(3–30 µM) has an inhibitive effect on sprouting. Effects of GA₃ application on shoot elongation were tested onsprouted bulbils. GA₃ promoted elongation when applied directlyto the shoots and inhibited it when applied to the bulbous parts. These results suggest that GA activates two opposing reactions—sprouting-promotingand sprouting-inhibiting—in these organs. The complicatedrelation between GA₃ or CCC concentrations and sprouting wereexplainable by assuming that the two counteractive reactionswere activated by GA in different degrees. ¹ Present address: Department of Biology, Faculty of Science,Yamagata University, Yamagata 990, Japan. (Received June 21, 1976; )