Interannual variability in a predator-prey interaction: climate, chaetognaths and copepods in the southeastern Bering Sea

The interaction of the chaetognath Sagitta elegans with thecopepod community of the southeast Bering Sea middle shelf wasexamined in relation to environmental conditions during 1995–1999.Predation impact was estimated for 2 years, 1995 and 1997, usinggut content analysis, experimentally derived digestion time(DT) and abundances of chaetognaths and prey. Pseudocalanusconcentrations correlated with water temperature and Calanusmarshallae with sea ice extent. Sagitta elegans were less abundantbut individuals were larger in 1995, when C. marshallae predominated,compared to 1997, when Pseudocalanus and Acartia were the primaryprey. Predation by S. elegans removed <1% standing stockday^–1 of Pseudocalanus or C. marshallae in 1995 and 1.7to 2.3% of Pseudocalanus in 1997. The percent of the copepodcommunity biomass required by chaetognaths was estimated tobe <1% in 1995 compared with 8–12% in 1997. Calanusmarshallae may be more vulnerable than Pseudocalanus to cumulativepredation effects because of its reproductive strategy. Theeffect of chaetognath predation on the copepod community dependson which copepod species is predominant and its susceptibilityto cumulative predation effects, as well as on daily predationimpact, both of which varied between years with different climaticconditions.     

Cytokinin Induces a Rapid Decrease in the Levels of mRNAs for Catalase, 3-Hydroxy-3-methylglutaryl CoA reductase, Lectin and Other Unidentified Proteins in Etiolated Cotyledons of Cucumber

Large-scale differential hybridization was performed to examinerapid changes in gene expression caused by a phytohormone, cytokinin,in etiolated cotyledons of cucumber (Cucumis sativus L.). Weisolated 86 cDNA clones for mRNAs whose levels decreased within2 h of the start of treatment with N⁶-benzyladenine (BA). Partialnucleotide sequences showed that some of the cDNAs were homologousto those for catalase, 3-hydroxy-3-methylglutaryl CoA reductase(HMGR) and a lectin. This is the first report that the levelsof the mRNAs for those proteins are regulated by a cytokininin darkness. Together with previous results [Teramoto et al.(1993) Physiol. Plant. 87: 584, (1994) Planta 193: 573, (1995)Planta 196: 387], the present study suggests that the cytokininact to lower the levels of mRNAs transcribed from various genesin etiolated cotyledons. (Received May 18, 1995; Accepted August 17, 1995)     

Molecular Cloning and Characterization of a cDNA for the r{beta} Subunit of a G Protein from Rice

We isolated a cDNA for the rß subunit of a heterotrimericG protein from rice (Oryza sativa L. cv. Nipponbare). The aminoacid sequence deduced from the cDNA was 76% and 94% homologusto the sequences of the rß subunits from Arabidopsisand maize (AGrß1 and ZGrß1), respectively. (Received July 28, 1995; Accepted December 25, 1995)     

Tobacco Nuclear Genes for Photosystem I Subunits, psaD, psaE and psaH Share an Octamer Motif Bound with Nuclear Proteins

In Nicotiana sylvestris, nuclear-encoded photosystem I (PSI)genes, psaD, psaE and psaH, share an octamer motif bound withthree phosphoproteins. This motif is not found in the chloroplastgenome. From the view point of endosymbiont hypothesis, theseresults suggest that a set of ancient PSI genes acquired a commoncis-element in the nucleus after they were transferred fromthe ancestral organelle. (Received March 20, 1995; Accepted August 9, 1995)     

A PRELIMINARY CLADISTIC ANALYSIS OF NORTH ATLANTIC OENOPOTA MOERCH, 1852 AND PROPEBELA IREDALE, 1918 (GASTROPODA: CONOIDEA)

The phytogeny of 23 species of the conoidean gastropods Oenopotaand Propebela from the North Atlantic is estimated in a parsimonyanalysis based on 26 morphological characters. Mangeha attenuata(Montagu, 1803) is used as outgroup. The results indicate thatmost Propebela species form a mono-phyletic group within theOenopota/Propebela complex, whereas Oenopota constitutes a paraphyleticassembly. The genus Curtuoma Bartsch, 1941 is probably non-monophyletic. (Received 11 September 1995; accepted 8 December 1995)     

The Biosynthetic Pathway of Astaxanthin in a Green Alga Haematococcus pluvialis as Indicated by Inhibition with Diphenylamine

The effect of diphenylamine on astaxanthin biosynthesis in Haematococcuspluvialis was studied. Cultures induced to produce astaxanthinaccumulated rß-carotene in the presence of the inhibitor.It was found that 30 µM diphenylamine specifically inhibitsthe biosynthesis of astaxanthin at the step of conversion ofrß-carotene to echinenone and canthaxanthin. The resultsimply that these two compounds are genuine intermediates inthe pathway of astaxanthin biosynthesis in H. pluvialis. (Received June 26, 1995; Accepted September 7, 1995)     

Photoactivation of the Electron Flow from NADPH to Plastoquinone in Spinach Chloroplasts

Intact chloroplasts from spinach showed a transient increasein Chl fluorescence after saturating illumination with actiniclight and its yield depended on the duration of illuminationand the intensity of the actinic light (AL). The increase waspartially suppressed when antimycin A was added immediatelyafter termination of the AL. The inhibited fluorescence increase,therefore, reflected the electron flow from the reductant(s)that had accumulated during the actinic illumination to theplastoquinone (PQ) pool via ferredoxin and the antimycin A-sensitiveCyt b-559 [Miyake et al. (1995) Plant Cell Physiol. 36: 743].Addition of dihydroxyacetone phosphate (DHAP) to chloroplastscaused the enhancement of the increase in fluorescence afterAL, which was inhibited by antimycin A. Decay of the transientlyraised fluorescence was retarded by 2-heptyl-4-hydroxyquinolineN-oxide and stigmatellin, suggesting that re-oxidation of thereduced PQ pool is coupled with the operation of Q-cycle. Althoughthe activity of the stromal enzyme system that supplies NADPHon addition of DHAP was constant irrespective of light or darkness,the capacity of the intact chloroplasts to show a DHAP-dependentfluorescence increase had a limited lifetime after AL was turnedoff. This result suggests that the antimycin A-sensitive Cytb-559 or ferredoxin-NADP reductase is activated by light anddeactivated in the dark. In ruptured chloroplasts, the additionof NADPH increased the dark fluorescence yield only in the presenceof Fd, which also was inhibited by antimycin A. Thus the photoregulatorymechanism of Cyt b-559 (Fd) in intact chloroplasts appearedto be lost when chloroplasts were ruptured. (Received June 21, 1995; Accepted September 25, 1995)     

Dihydrokaempferol Glucoside from Cotyledons Promotes Flowering in Pharbitis nil

An extract of cotyledons of Pharbitis nil, which had been exposedto short-day conditions, was tested for flower-promoting activityin a shoot-tip assay system in vitro. The crude extract hadno flower-promoting activity, however, after partitioning ofthe crude extract with dichloromethane, the resulting aqueousfraction had flower-promoting activity. This activity was separatedinto two fractions by column chromatography on Toyopearl HW-40.One active fraction was identified as dihydrokaempferol-7-O-rß-D-glucoside(DHK-glc). This compound exhibited flower-promoting activityat the extremely low concentration of 4.4x10^-9. (Received April 25, 1995; Accepted August 11, 1995)     

Touch-Inducible Genes for Calmodulin and a Calmodulin-Related Protein Are Located in Tandem on a Chromosome of Arabidopsis thaliana

Genes for calmodulin and calmodulin-related proteins in Arabidopsisare up-regulated by a variety of physical stimuli, which includerain, wind and touch [Braam and Davis (1990) Cell 60: 357].We have isolated five genes for calmodulin (AtCALl, 2, 3, 5,6) and one gene for a calmodulin-related protein (AtCAL4) froman Arabidopsis genomic library. Touch stimulus of Arabidopsisplants induces the accumulation of mRNA transcribed from AtCAL4andAtCAL5, but not from the other isolated genes. The two touch-induciblegenes are arrayed in tandem with a short intergenic region of700 bp but they show different organ-specific patterns of expression. (Received April 27, 1995; Accepted July 20, 1995)     

cDNA Cloning and Characterization of a Gibberellin-Responsive Gene in Hypocotyls of Cucumis sativus L.

A cDNA clone corresponding to a gibberellin-responsive gene(CRG16) was isolated from cucumber hypocotyls. CRG16 was deducedto encode an extremely hydrophobic protein of 65 amino acids.The deduced sequence exhibited no significant homology to otherproteins. Levels of CRG16 mRNA reflected the gibberellin-inducedelongation of cucumber hypocotyls. (Received December 16, 1995; Accepted April 22, 1996)     

RADULAR PRODUCTION RATES IN TWO SPECIES OF LACUNA TURTON (GASTROPODA: LITTORINIDAE)

The molluscan radula is a dynamic organ, both in terms of itsuse and production. New rows of teeth are constantly producedat the posterior end of the radula, while older, worn teethare shed anteriorly, producing a dynamic equilibrium. We useda cold-shock to mark the radular ribbon and measure tooth rowproduction rates in two gastropod species, Lacuna vincta (Montagu)and L. vanegata Carpenter. We found that the average tooth rowproduction rate at 10–11°C did not differ betweenthese two species, and was 2.94 (SE = 0.002) rows per day forLacuna vincta and 2.97 (SE = 0 002) for L. vanegata Inter-individualvariability in production rate was very low, and was correlatedwith shell length, smaller individuals had slightly higher productionrates. The total length of the radular nbbon varied greatlyamong individuals, ranging from 47 to 94 (2.57 to 5.68 mm) rowsin L vincta and 53 to 99 rows (2.80 to 7.14 mm) in L vanegata,and was only somewhat correlated with the length of the shelLThis great variability will result in large differences amongindividuals in the time it takes to replace the radula totally,from 14.96 to 35.44 days in L vincta and from 17 43 to 39 69days in L. vanegata. (Received 1 September 1995; accepted 20 November 1995)     

SOME OBSERVATIONS ON THE DIET AND DISTRIBUTION OF NUDIBRANCHS AT SIGNY ISLAND, ANTARCTICA

Observations were made on the diet and distribution of eightspecies of nudibranchs found in Borge Bay, Signy Island, Antarctica.Specimens from seven sites were examined in situ on four separateoccasions during 1992 and 1993 using SCUBA. A small collectionfor identification was also made Six of the eight species presentwere identified, and the first ecological data for at leastone species (Charcotia granulosa) were recorded. Notaeolidiagigas was feeding principally on hydroids of the genus Tubulariaover the entire depth range surveyed (3–36 m), and wasmost abundant in shallow water, whereas Truomella belli wasonly found at deeper sites, mostly on an octocoral of the genusAscolepis. Charcoaa granulosa and Pseudotritoma gracilidensappeared to be specialist bryozoan feeders and, as has beenfound at other locations, Austrodoris kerguelenesis specialisedon the demosponge Dendnlla antarcnca. Two unidentified aeolidspecies occurred almost entirely on particular hydroids andthe prey of Tritonia antarctica was not apparent. The physicalsize of Antarctic nudibranchs may have important implicationsto the type of prey and feeding strategy used by different species. (Received 11 May 1995; accepted 3 December 1995)     

Biochemical, Immunochemical and Immunohistochemical Identification of Myosin Heavy Chains in Cultured Cells of Catharanthus roseus

In the pollen tubes of the lily Lilium longiflorum, myosin,composed of 170-kDa heavy chains is responsible for the intracellulartransport of organelles [Yokota and Shimmen (1994) Protoplasma177: 153]. Polypeptides of 170 kDa with similar antigenicityto this pollen-tube myosin have also been found in other angiospermcells [Yokota et al. (1995) Protoplasma 185: 178]. To clarifythe role of this type of myosin in cytoplasmic streaming, weprepared partially purified myosin fraction from cultured cellsof Catharanthus roseus by co-precipitation with F-actin. Ina motility assay in vitro with this fraction, rhodamine-phalloidin-labeledF-actin moved with an average velocity of 10.7 µm s^-1.This sliding velocity was similar to that of the cytoplasmicstreaming observed in intact cultured cells. Antibodies raisedagainst the 170-kDa heavy chain of pollen-tube myosin recognizedonly a single polypeptide of 170 kDa in this partially purifiedfraction. The same polypeptide was also identified by theseantibodies in a crude extract of proteins from cultured cells.The myosin-specific fluorescence was concentrated around thenuclei and was associated with particles of various sizes. Duallocalization using antibodies against myosin and against actinrevealed that these particles were preferentially co-localizedwith actin filaments. On the other hand, no component of thecrude extract or of the partially purified myosin fraction cross-reactedwith antibodies against heavy chains of myosin II from animalcells. These results suggest that the 170-kDa polypeptide is the myosinheavy chain and that this myosin generates the motive forcefor cytoplasmic streaming in cultured cells of Catharanthusroseus. (Received March 28, 1995; Accepted September 14, 1995)     

Purification and Characterization of Phosphoribulokinase from the Cyanobacterium Synechococcus PCC7942

Phosphoribulokinase (PRK) was purified to electrophoretic homogeneityfrom Synechococcus PCC7942 with high specific activity. Molecularmasses of the native enzyme and its subunit were 178 and 42kDa, respectively. Cys-17 and Cys-38 were conserved in the cyanobacterialPRK, but 18 amino acid residues between them were missing amongthe 40 residues found in higher plant PRKs. (Received February 1, 1995; Accepted July 27, 1995)