Ecological studies on the phytoplankton of Korsfjorden, western Norway. The dynamics of a spring bloom seen in relation to hydrographical conditions and light regime

The investigation was carried out at one station in Korsfjorden,a typical deep silled fjord of western Norway. During 14 cruisesfrom 4 February to 30 June 1977 ATP, chlorophll a, phaeopigmenta, and in situ ¹⁴C-assimilation were measured in the net (>30µm), nano and ultraplankton (<5 µm). Sampleswere collected from five light depths within euphotic zone.The impact of hydrographical conditions and light regime onthe bloom dynamics was also studied. In the periods 4 February-7 March and 13 April-30 June, ultraplankton contributed >60%to the total primary production while net and nanoplankton dominatedfrom 7 March to 13 April. The diatoms Skeletonema costatum,Chaetoceros compressits and C. debilis, and Rhizosolenia hebetatavar. semispina made up the main part of the biomass on 21 March,28 March and 4 April respectively. A shade adapted diatom societywas located at the top of the nutricline in late June with S.costatum, Chaetoceros spp., and Thalassiosira spp. as the dominantspecies. The highest assimilation number of eight for the netplankton and four for the ultraplankton were found at the depthof 32% light intensity on 28 March and 24 May respectively.Linear relationships were found between chlorophyll a and ATPfor the different size fractions with regression slopes rangingfrom 4.3 to 5.8. The total primary production for the periodof investigation was calculated to 74 g C m^–2. Light regimeand water column stability were decisive factors for the outburstof the first diatom bloom in late March. Grazing on net planktondiatoms increased during late March-early April. Changes inthe longshore wind-stress component were found to be essentialfor the understanding of the bloom dynamics.     

Spatial structure of eukaryotic ultraplankton community in the northern South China Sea

Spatial distribution, diversity and composition of eukaryotic ultraplankton community of the northern South China Sea (nSCS) surface water and the relationship with the in situ water environment were investigated by the method of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). A total of 18 DGGE intensive bands were detected and the sequence analysis of these DGGE bands revealed that Alveolata was the dominant eukaryotic ultraplankton group of surface water in the nSCS (50%). Other species belonged to Bicoecea, Bolidophyceae, Polycystinea and Chlorophyta, which accounted for less proportion of eukaryotic ultraplankton in the study area. Unweighted pair group method with arithmetic averages clustering of the sampling stations indicated that all stations were classified mainly based on geographical proximity. Redundancy analysis (RDA) was employed to further investigate the relationships between DGGE band pattern and the environmental variables. Based on the RDA analysis, temperature, salinity, phosphorus and silicate were the important factors to shape the eukaryotic ultraplankton community composition in the nSCS.     

ERRATA

The legend to Figure 3 was incomplete. The correct legend isgiven below:Fig. 3. IF results for the Gulf of Maine and adjacentslope in the surface (top row), top of thermocline (second row),chlorophyll maximum (third row) and at the base of the thermocline(fourth row). Along the x-axis, stations are plotted in orderof approximate distance from the shore (see Figure 1). The y-axescorrespond to: (A) total eukaryotic algae counts; (B) % of totalcounts labeled by antiserum to E.huxleyi (clone BT6); (C) %of total counts labeled by antiserum to P.provasolii (48-23);(D) % of total counts labeled by antiserum to P.subviridis (clonePELA CL2); (E) % of total counts labeled by antiserum to T.oceanka(clone 13-1); (F) % of total counts labeled by antiserum tochlorophyte clone B6125. * = not available. The last sentence of page 46 should read: We attribute this to a loss of eukaryotic algal cells such thatin stored samples the percentage labeled may be overestimated.     

A novel {beta}-galactosidase gene isolated from the bacterium Xanthomonas manihotis exhibits strong homology to several eukaryotic {beta}-galactosidases

The gene encoding a ß-galactosidase from Xanthomonasmanihotis was cloned into Escherichia coli. The gene resideson a 2.4 kb DNA fragment which was isolated from a partial Sau3Alibrary in the cloning vector pUC19 using 5-bromo-4-chloro-3-indolyl-ß-D-galactopyranoside(X-gal) as the selection. The enzyme produced by the clone hasa specificity for ß1-3->ß1-4-linked galactose.The nucleotide sequence of the gene was determined. The deducedprotein sequence contained 597 amino acids yielding a monomericmolecular mass of 66 kDa. The cloned ß-galactosidaseshowed no similarity to any known prokaryotic ß-galactosidase.However, extensive similarity was observed with eukaryotic ß-galactosidasesfrom animals, plants and fungi. The strongest similarity waswith the ß-galactosidases found hi the human and mouselysosomes (42 and 41% identity, respectively). Alignment ofthe X.manihotis and eukaryotic ß-galactosidase sequencesrevealed seven highly conserved domains common to each protein.Additionally, Domain 1 in X.manihotis showed similarity to regionswithin catalytic domains from seven xylanases and cellulasesbelonging to family 10 of glucosyl hydrolases. A region spanningDomain 2 showed similarity to the catalytic domain of endo ß1-3glucanases from tobacco and barley. cellulase ß-galactosidase G_M$$$gangliosidosis Morquio B syndrome Xanthomonas     

Response to Waterlogging and Differing Sensitivity to Divalent Iron and Manganese in Clones of Dactylis glomerata L. derived from Well-drained and Poorly-drained Soils

Clonally propagated plants of Dactylis glomerata derived froma well-drained, heavily grazed cliff habitat (clone L) and froman undergrazed poorly-drained soil (clone A) were tested forwaterlogging tolerance in soil-culture. Water-logging did notaffect the two clones differentially, a result, which contrastedstrongly with that of a previous experiment in which simulatedgrazing (clipping to 20 cm) unexpectedly caused clone A to beless tolerant of waterlogging than clone L. Maximum leaf andleaf sheath length was reduced more by water-logging in cloneL than in clone A (P < 0.05). In solution-culture when providedwith factorial combinations of 0.5, 5 and 50 mg dm^–2 ofFe²⁺ and Mn²⁺ the shoot dry weight yield of the dry-soil clonewas reduced more than that of the wet-soil clone by 50 mg Fedm^–3 irrespective of Mn²⁺ concentration (P < 0.01)but the reduction of growth was less at higher Mn²⁺ concentrations.Fifty milligrams of Mn²⁺ dm^–3 reduced the growth of thedry soil clone but increased the growth of the wet soil clonewith Fe²⁺ at 5 mg dm^–2 (P < 0.05). Iron at 0.5 mg dm^–2was suboptimal for shoot growth of both clones at any levelof Mn²⁺ and caused more severe leaf chlorosis in the wet soilclone. Leaf tissue of clone L contained more iron than thatof clone A after waterlogging (P < 0.01) but in solutionculture, though increasing iron from 0.5 to 50 mg dm^–3almost doubled leaf iron content (P < 0.001), the interactionClones x Mn x Fe just failed to reach significance at P <0.05. The manganese content of leaf tissue from the two clonesvaried differently in response to solution manganese (Clonesx Mn P < 0.01), clone A showing a slightly greater increaseof manganese content at high solution concentration. Iron at50 mg dm^–3 suppressed Mn uptake (Mn x Fe, P < 0.001)in both clones. The two clones thus show marked environmentaladaptation to the chemistry of wet and dry soils. Dactylis glomerata, Cocksfoot grass, Orchard grass, waterlogging, iron, manganese, toxicity, deficiency, ecotypes     

Escherichia coli as an expression system for K(+) transport systems from plants

The value of theEscherichia coli expression system has long been establishedbecause of its effectiveness in characterizing the structure andfunction of exogenously expressed proteins. When eukaryotic membraneproteins are functionally expressed in E. coli, thisorganism can serve as an alternative to eukaryotic host cells. A fewexamples have been reported of functional expression of animal andplant membrane proteins in E. coli. This mini-review describes the following findings: 1) homologousK⁺ transporters exist in prokaryotic cells and ineukaryotic cells; 2) plant K⁺ transporters canfunctionally complement mutant K⁺ transporter genes inE. coli; and 3) membrane structures of plant K⁺ transporters can be elucidated in an E. colisystem. These experimental findings suggest the possibility ofutilizing the E. coli bacterium as an expression system forother eukaryotic membrane transport proteins.

     

Comparison of intestinal folate carrier clone expressed in IEC-6 cells and in Xenopus oocytes

We recently identified a cDNA clone frommouse small intestine, which appears to be involved in folate transportwhen expressed in Xenopus oocytes. Theopen reading frame of this clone is identical to that of the reducedfolate carrier (RFC) (K. H. Dixon, B. C. Lanpher, J. Chiu, K. Kelley,and K. H. Cowan. J. Biol. Chem. 269: 17-20,1994). The characteristics of this cDNA clone [previously referred toas intestinal folate carrier 1 (IFC-1)] expressed inXenopus oocytes, however, were foundto be different from the characteristics of folate transport in nativesmall intestinal epithelial cells. To further study these differences,we determined the characteristics of RFC when expressed in anintestinal epithelial cell line, IEC-6, and compared the findings toits characteristics when expressed inXenopus oocytes. RFC was stablytransfected into IEC-6 cells by electroporation; its cRNA wasmicroinjected into Xenopus oocytes.Northern blot analysis of poly(A)⁺RNA from IEC-6 cells stably transfected with RFC cDNA (IEC-6/RFC) showed a twofold increase in RFC mRNA levels over controls. Similarly, uptake of folic acid and 5-methyltetrahydrofolate (5-MTHF) by IEC-6/RFCwas found to be fourfold higher than uptake in control sublines. Thisincrease in folic acid and 5-MTHF uptake was inhibited by treatingIEC-6/RFC cells with cholesterol-modified antisense DNAoligonucleotides. The increase in uptake was found to be mainly mediated through an increase in the maximal velocity(V_max) of theuptake process [the apparent Michaelis-Menten constant(K_m) alsochanged (range was 0.31 to 1.56 µM), but no specific trend wasseen]. In both IEC-6/RFC and control sublines, the uptake of bothfolic acid and 5-MTHF displayed 1)pH dependency, with a higher uptake at acidic pH 5.5 compared with pH7.5, and 2) inhibition to the sameextent by both reduced and oxidized folate derivatives. Thesecharacteristics are very similar to those seen in native intestinalepithelial cells. In contrast, RFC expressed inXenopus oocytes showed1) higher uptake at neutral andalkaline pH 7.5 compared with acidic pH 5.5 and2) higher sensitivity to reducedcompared with oxidized folate derivatives. Results of these studiesdemonstrate that the characteristics of RFC vary depending on the cellsystem in which it is expressed. Furthermore, the results may suggestthe involvement of cell- or tissue-specific posttranslationalmodification(s) and/or the existence of an auxiliary proteinthat may account for the differences in the characteristics of theintestinal RFC when expressed inXenopus oocytes compared with whenexpressed in intestinal epithelial cells.

     

Agrobacterium rhizogenes Mediated Transformation of the Forage Legumes Medicago sativa and Onobrychis viciifolia

Three cultivars of M. sativa and one cultivar of O. viciifoliawere evaluated for their response to inoculation with A. rhizogenesstrain A4T (containing pRiA4b). A cultivar-dependent responsewas observed in M. sativa with 94%, 25%, and 4% of infectedstem explants producing transformed roots in the cultivars Vertus,Regen-S, and Rangelander, respectively. In O. viciifolia cv.Hampshire Giant, an explant-dependent response was observedwith 78% and 50% of seedling cotyledon and hypocotyl explantsresponding, respectively. Leaf explants failed to produce transformedroots. Transformed roots showed plagiotropic and negativelygeotropic growth on hormone-free agar MS medium. Productionof transgenic shoots from O. viciifolia root cultures occurredspontaneously. Recovery of transgenic plants from M. salivacv. Rangelander was achieved by transfer of callus (inducedon UM medium containing 2·0mg dm^–3 2,4-D and 0·25mg dm^–3 kinetin) to MS medium containing 0·5 ingdm^–3 BAP and 0·05 mg dm^–3 NAA. Cultured rootsof both species synthesized opines (agropine and mannopine).Extensive morphological variation was observed in plants ofM. sativa (clone Al) and O. viciifolia (clone A4Tl) establishedin the glasshouse. DNA sequences homologous to TL-DNA and TR-DNAwere present in root clones and regenerated plants. Key words: Agrobacterium rhizogenes, Medicago sativa, Onobrychis viciifolia, transformed roots, transgenic plants     

Direct Somatic Embryoid Formation on Immature Embryos of Trifolium repens, T. pratense and Medicago sativa, and Rapid Clonal Propagation of T. repens

By direct somatic embryogenesis in vitro a clone of asepticplantlets can be raised from a single immature embryo of Trifoliumrepens (white clover) within about 6 weeks of pollination. Embryoidsare induced directly from intact zygotic embryonic tissue ona culture medium containing 0·025 or 0·05 mg 1^–1BAP and 1·0 g 1^–1 yeast extract. Similar directsomatic embryogenesis has also been achieved for Trifolium pratense(red clover) and Medicago sativa (lucerne). Applications ofembryo propagation by direct somatic embryogenesis are discussed,particularly in relation to multiple screening of host genotypesfor analysis of host/pathogen and legume/Rhizobium interactions. Trifolium repens L., Trifolium pratense L., Medicago sativa L., clover, lucerne, tissue culture, embryoid, somatic embryogenesis, legumes     

Nucleotide Sequence Surrounding the Locus Marker D21S246 on Human Chromosome 21

Most ofthe human Not I linking clones identified to date areconsidered to be derived from CpG islands because ofthe recognitionsequence of this enzyme, and CpG islands have been reportedto be located around the 5' regions of genes. As a pilot study,we determined the complete nucleotide sequence (41,924 bp) ofa human cosmid clone (LL21NC02Q7A10) containing the marker D21S246originating from a Not I linking clone. As a result of sequenceanalysis, we successfully mapped and revealed the genomic genestructure for KIAA0002 previously reported as a cDNA clone.This gene consists of 15 exons and was shown to exist at theD21S246 locus on human chromosome 21q21.3–q22.1. Theseresults demonstrated that genomic marker-anchored DNA sequencingis a useful approach for the human genome project.     

Characterization and expression of an mRNA encoding a wound-induced (Win) protein from ethylene-treated tomato leaf abscission zone tissue

A cDNA clone (TAB7) encoding a putative woundinduced (Win) proteinhas been isolated from a tomato (Lycopersicon esculentum Mill.cv. Ailsa Craig) leaf abscission zone cDNA library using a differentialscreening strategy. The clone has a high degree of homologyat the amino acid level to both the potato win1 and 2 genes,Hevea brasiliensis hevein and Nicotiana tabacum PR-4a and PR-4bproteins. The mRNA encoded by TAB7 is up-regulated within 12h of exposure to ethylene (10µl l^–1) and its expressionincreases steadily within the cells comprising the leaf abscissionzone and to a lesser extent in the adjacent non-zone tissue.This rise precedes the onset of cell separation. Southern analysisindicates that the mRNA is encoded by either a single gene ora small gene family. The role of the protein during abscissionis discussed. Key words: Lycopersicon esculentum, abscission zone, ethylene, tomato, wound-induced proteins     

14C Fixation and Translocation in two Clones of Sugarcane with Contrasting Rates of Sucrose Uptake in vitro

The rates of ¹⁴CO₂ fixation and translocation of ¹⁴C labelledassimilates were measured in field experiments at two timesof the day in two sugar-cane clones known to have differentrates of sucrose uptake in vitro but the same weight of leafper unit weight of cane. The rate of ¹⁴CO₂ fixation and the velocity and rate of translocationwere significantly greater at both times in the clone with thehigher rate of sucrose uptake in vitro. The velocities of translocationwere 2.18 and 2.36 cm/min^–1 for the clone with high sucroseuptake and 1.46 cm min^–1 at both times in the clone withlow uptake. It is suggested that among sugar-cane clones the ability oftheir canes to store sugar may play a part in determining theirrates of photosynthesis and translocation.     

High abundance of picoplankton-ingesting ciliates during late fall in Lake Kinneret, Israel

Small, aloricate ciliates dominated the biomass of heterotrophicprotists throughout the water column at the end of the periodof stratification in Lake Kinneret, Israel The integrated biomassof cilates was 5–20 times that of heterotrophic flagellatesDuring incubation experiments, ciliate growth rates in cpilimneticwater corresponded to population doubling times of 9.6–19.4h, while flagellate populations showed no growth. Most of thealiates were small forms (10–30 µm long), includingscuticocihates, choreotnchs, Coleps spp. and Colpoda spp., andappeared to be consuming bacteria, coccoid cyanobacteria, and<5 µm eukaryotic algae. Grazing rates of cihate assemblageson picoplankton in the epilimnion, as determined by the uptakeof fluorescently labeled bacteria and cyanobactena, ranged from62 to 86 nl cell^–1 h^–1 Colpoda steini, isolatedfrom lakewater, grew on a cultured freshwater Synechococcussp with a doubling time of 4.5 h, and a gross growth efficiencyof 48% The estimated daily requirements of ciliates for growthapproximately equalled total phytoplankton production. We calculatedthat ciliates in the epilimnion were clearing 4–10% ofthe bacterioplankton and cyanobactenal standing stocks per daySince this would not be sufficient food consumption to meetdaily carbon requirements of the aliates, it is likely thatthese organisms were also grazing a significant amount of autotrophicand heterotrophic eukaryotic cells in Lake Kinneret.     

Cloning and Mapping of Telomere-Associated Sequences from Rice

We have isolated three telomere-associated sequences from riceusing cassette-ligation-mediated polymerase chain reaction (PCR).Each of the obtained clones hybridized to the terminal of oneor several rice chromosome arms. The telomeres recognized bythe clones displayed a high level of polymorphism between tworice varieties, Nipponbare (a japonica variety) and Kasalath(an indica variety). Variability in the chromosome termini wasalso detected among individual F₂ progeny plants, which werederived from a cross between the two rice varieties. One clonecontaining telomere-associated sequences was located to oneend of chromosome 5, and another clone to one end of chromosome11. For another clone, non-allelic segregation of polymorphichybridization bands was observed between japonica and indicarice; this clone was mapped to one end of chromosome 12 in japonicaand to one end of chromosome 11 in indica rice. This indicatesan exchange of termini between nonhomologous chromosomes.     

Cloning of the Pumpkin Ascorbate Oxidase Gene and Analysis of a Cis-Acting Region Involved in Induction by Auxin

A genomic clone encoding ascorbate oxidase was isolated frompumpkin (Cucurbita sp.)- This gene is consisted of four exonsand three introns. Analyses of the promoter fusion to ß-glucuronidasereporter gene by transient expression assay in pumpkin fruittissues suggested the existence of a cis-acting region responsiblefor auxin regulation. (Received November 28, 1996; Accepted March 8, 1997)     

Cloning of murine glycosyl phosphatidylinositol anchor attachment protein, GPAA1

Glycosyl phosphatidylinositols (GPIs) are usedto anchor many proteins to the cell surface membrane and are utilizedin all eukaryotic cells. GPI anchoring units are attached to proteins via a transamidase reaction mediated by a GPI transamidase complex. Weisolated one of the components of this complex,mGPAA1 (murine GPI anchor attachment), by the signalsequence trap method. mGPAA1 cDNA is about 2 kb in lengthand encodes a putative 621 amino acid protein. The mGPAA1gene has 12 small exons and 11 small introns. mGPAA1 mRNA isubiquitously expressed in mammalian cells, and in situ hybridizationanalysis revealed that it is abundant in the choroid plexus, skeletalmuscle, osteoblasts of rib, and occipital bone in mouse embryos. Itsexpression levels and transamidation efficiency decreased withdifferentiation of embryonic stem cells. The 3T3 cell lines expressingantisense mGPAA1 failed to express GPI-anchored proteins onthe cell surface membrane.

     

Role of Copper Binding, Absorption, and Translocation in Copper Tolerance of Agrostis gigantea Roth

The capacity of roots to accumulate and retain copper was examinedin two clones of Agrostis gigantea which differ in their toleranceto excess copper. Root elongation growth in the non-tolerantclone was completely inhibited by 16 mmol m^–3 Cu whereas40 mmol m^–3 was required for inhibition in the tolerantclone. The amount of readily exchangeable copper was greaterin roots of the tolerant clone than in the non-tolerant clone.The higher capacity for binding copper did not prevent the entryof copper into the cells of intact or excised roots of the tolerantclone. Roots of both clones contained similar amounts of copperafter removal of the readily exchangeable fraction. More copperwas translocated to the shoots of the tolerant than the non-tolerantclone. The explanation of copper tolerance in Agrostis giganteamust be sought in areas other than those of differences in grosscopper absorption and retention by roots.