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1.
Lemna paucicostata, normally a short-day plant, can be inducedto flower under long-day conditions by providing a cytokininin a medium containing a high level of ferric citrate (5 x 104M).Interestingly, when a cytokinin and EDDHA are present togetherin the medium, flowering is induced even at low levels of iron(105 and 5 x 105M ferric citrate). However, inthe absence of a cytokinin, flowering takes place only undershort days. (Received September 30, 1968; ) 相似文献
2.
The association between the green alga Coccomyxa parasitica
(Chlorococcales)and the mussel Mytilus edulis chilensis at Goose Green, Falkland
Islandsis reported. C. parasitica occurred within the soft tissueswith an overall
infestation rate of 16%. The highest levelsof infestation (23%) occurred in
individuals from the middleof the main mussel bed, with considerably lower levels of infestation
inthe upper and lower regions (<1% and 5% respectively). Noconsistent
seasonal pattern in infestation rate was detectedbetween September 1993 and February 1996. C. parasitica wasmost commonly observed in tissues located in the posterior territoryof
the host, in areas most directly exposed to light. Tissuesof infested mussels were rather watery
and translucent and theadductor muscle appeared weak and stringy. During the summermonths
when Falkland mussels are in peak reproductive condition,dry flesh weight of infested mussels
was significantly lowerthan noninfected mussels of comparable size suggestingthat
infestation by C. parasitica may reduce reproductive output.However it is uncertain
whether poor condition of the host isdue to the presence of the parasitic alga or whether C.
parasiticainfests only those mussels that are already in poor condition.
1 Present address: 3, St Marys Walk, PO Box 530, Stanley, Falkland
Islands (Received 10 June 1998; accepted 8 September 1998) 相似文献
3.
Synechococcus PCC 7942 contains two fructose-1,6-bisphosphataseisozymes (FBPase-I and FBPase-II), while Synechocystis PCC 6803has only one (FBPase-I) in spite of the occurrence of two FBPaseisozyme genes [Tamoi et al. (1998) Biochim. Biophys. Acta 1383:232]. We now demonstrate that disruption of the gene encodingFBPase-II (fbp-II) with a kanamycin resistance gene cartridgedoes not affect cell growth, Chl content, or CO2 assimilationin Synechococcus PCC 7942, and disruption of the gene encodingFBPase-I (fbp-I) is a lethal mutation in both cyanobacteria.Accordingly, it is clear that FBPase-I is necessary to sustainphotosynthesis and gluconeogenesis in cyanobacteria. (Received September 10, 1998; Accepted December 10, 1998) 相似文献
4.
Protoplasts were successfully isolated from internodal callustissues of both Oxalis glaucifolia and O. rhombeo-ovata whenthey were digested in a solution containing 0.1% (w/v) MacerozymeR-10, 0.5% (w/v) cellulase Onozuka R-10 and 0.3 mmol m3sucrose. Protoplasts proliferated to give cell colonies on Gamborget al.'s B5 medium supplemented with 0.3 mmol m3 mannitol,0.5 mg dm32, 4-D, and 2.0 mg dm3 kinetin. Calluswas produced upon transfer of cell colonies to Murashige andSkoog medium containing 2.0 mg dm3 l-naphthaleneaceticacid (NAA) and 0.1 mg dm3 kinetin for O. glaucifolia,or with 5.0 mg dm3 NAA and 0.5 mg dm3 6-benzylaminopurine,for O. rhombeo-ovata. Plants were regenerated from O. glaucifoliaprotoplasts on a medium containing 0.1 mg dm3 NAA, 1.0mg dm3 kinetin and 1.0 mg dm3 gibberellic acid,but only vascular nodules were differentiated by O. rhombeo-ovataprotoplast-derived calli. Key words: Tissue culture, protoplasts, plant regeneration, Oxalis spp 相似文献
5.
Shiota Hajime; Satoh Rika; Watabe Ken-ichi; Harada Hiroshi; Kamada Hiroshi 《Plant & cell physiology》1998,39(11):1184-1193
A carrot gene homologous to the ABI3 gene of Arabidopsis wasisolated from a carrot somatic embryo cDNA library and designatedC-ABI3. The sequence of C-ABI3 was very similar to those ofABI3 of Arabidopsis and VP1 of maize in certain conserved regions.The expression of C-ABI3 was detected specifically in embryogeniccells, somatic embryos and developing seeds. Thus, expressionof C-ABI3 was limited to tissues that acquired desiccation tolerancein response to endogenous or exogenous abscisic acid (ABA).Endogenous levels of ABA in seeds increased transiently andthen desiccation of seeds started. The expression of C-ABI3in developing seeds was observed prior to the increase in levelsof endogenous ABA that was followed by desiccation of seeds.In transgenic mature leaves in which C-ABI3 was ectopicallyexpressed, expression of ECP31, ECP63 and ECP40 was inducedby treatment with ABA, which indicates that the expression ofECP genes was controlled by the pathway(s) that involved C-ABI3and ABA. This suggests that C-ABI3 has the same function asVP1/ABI3 factor in carrot somatic embryos. (Received March 4, 1998; Accepted September 4, 1998) 相似文献
6.
The rate of short-term accumulation of [35S]sulfite in Chlorellavulgaris cells was found to be strongly dependent on the pHof the medium. The rate increased with decreased pH, and theincrease in rate closely paralleled the increase in the concentrationof the un-ionized form of sulfite. When the pH of the mediumwas increased, fast accumulation ceased immediately. The rateof accumulation showed a strong temperature dependence, withan apparent temperature coefficient of 1.93 per 10°C rise,between 10 and 25°C. Because pKa values of sulfite shiftwith temperature, the rates were corrected by dividing by theconcentration of the un-ionized form of sulfite present at therespective temperatures. The temperature coefficient was thenfound to decrease to 1.45. When cells which had been allowedto accumulate [35S]sulfite for 20 min were transferred to amedium containing no sulfite, more than 50% of the accumulated[35S] was released into the medium in 20 min. Our results arecompatible with a simple diffusion model of SO2 transport intoChlorella cells. (Received September 26, 1996; Accepted January 20, 1997) 相似文献
7.
An efficient Agrobacterium tumefaciens-mediated transformation and regeneration system for cotyledons of spinach (Spinacia oleracea L.) 总被引:2,自引:0,他引:2
An efficient transformation and regeneration system was established for the production of transgenic spinach (Spinacia oleracea L.) plants. Cotyledon explants were infected with Agrobacterium tumefaciens strain LBA4404 carrying the selectable marker gene, neomycin phosphotransferase II (nptII), and the reporter gene smgfp, encoding soluble-modified green-fluorescent protein, driven by the cauliflower mosaic virus 35S promoter. The infected explants
were cultured on Murashige and Skoog medium, containing 1 mg/l benzyladenine and 0.4 mg/l naphthaleneacetic acid. Shoots were
regenerated on selection medium containing 50 mg/l kanamycin. Regenerated kanamycin-resistant shoots were rooted on medium
containing 1 mg/l indolebutyric acid and subsequently grown in soil in the greenhouse. Southern blot analysis indicated that
the smgfp gene had been integrated into the spinach genome. Northern and Western blots showed that the smgfp gene was expressed in progeny plants.
Received: 31 March 1998 / Revision received: 27 September 1998 / Accepted: 10 Ocotber 1998 相似文献
8.
Tidally driven distribution of phytoplankton blooms in a shallow, macrotidal estuary 总被引:2,自引:0,他引:2
The influence of the ebb tide on the abundance and distributionof bloom-forming species, as well as the mechanisms for theselection of those species which remain, were investigated inthe shallow, tidal-flushed Urdaibai estuary, north Spain. Phytoplanktonwas collected monthly from May to September 1998 during differenttidal conditions (neap-spring) at five stations along the salinitygradient of the estuary. During the neap tides of May, Leptocylindrusdanicus dominated in the lower estuary, together with Thalassiosiraguillardii and Peridinium foliaceum in the upper segment; T.guillardiiexperienced the broadest displacement along the estuary. Duringthe June and July cruises, coinciding with mid-tidal amplitudesand high temperatures, Peridinium quinquecorne densely aggregatedin the upper estuary at the slack high tide, whereas Chaetocerossalsugineum bloomed at the intermediate stations. Cyclotellaatomus and Protoperidinium achromaticum reached high concentrationsin the upper zone only during the late stages of the ebb. Duringthe spring tides of September, Prorocentrum minimum, Heterocapsapygmaea and Heterocapsa rotundata appeared in the lower marineestuary, being washed out at low tide. By contrast, the diatomsSkeletonema costatum, Thalassiosira guillardii and Cyclotellaatomus were the most abundant species in the upper reaches,peaking during the ebb. Physical trapping and high water residencetimes served to retain blooming species in the upper estuary.The intense growth of the estuarine diatoms may compensate forthe advective seaward losses of cells during the ebb, thus allowingthe development of stable populations in the estuary. Only Peridiniumquinquecorne seems to combine an endogenous tidal rhythm witha photic response to remain in the tidal area of the estuary. 相似文献
9.
Effects on positive phototaxis and the cell motility of 7 cationsin 5mM MOPS (morpholinopropane sulfonic acid) buffer (pH 7.0)containing 0.16 mM NaCl, 0.68 mM KCl, 0.5 mM CaCl2 and 0.16mM MgCl2 were studied in the unicellular flagellate Cryptomonaswith a photoelectrical measuring apparatus and photomicrography.When calcium ion was removed from the medium by adding 1 mMEGTA (ethylene glycol-bis-(ß-amino-ethylether)-N,N'-tetraaceticacid), the phototactic response was totally inhibited, but theswimming rate was not much affected. The effect of EGTA waspartially reversed by the addition of 1 mM CaCl2. When 15mMKCl or RbCl was added to the medium, phototaxis was greatlyinhibited, but there was no significant influence on the swimmingrate. Similar but less inhibitory effects were induced in thepresence of NaCl, LiCl and CsCl. KCl-induced inhibition waspartially removed by the addition of 15 mM CaCl2 or MgCl2. (Received June 25, 1982; Accepted September 27, 1982) 相似文献
10.
In vitro-grown shoot tips of five tetraploid potato (SolanumtuberosumL.) clones were cryopreserved by vitrification. Excisedshoot tips (0.50.7 mm) were pre-cultured on filter paperdiscs over half strength liquid Murashige and Skoog (MS) mediumsupplemented with 8.7 µMGA3and different combinationsof sucrose (0.3, 0.5 and 0.7M) plus mannitol (0, 0.2 and 0.4M)for 2 d under a 16 h photoperiod at 24 °C. The pre-culturedshoot tips were either successively loaded with 20 and 60% PVS2 solutions or directly exposed to concentrated vitrificationsolution before physical vitrification during liquid nitrogentreatment. The vitrified shoot tips were warmed rapidly andtreated with dilution mixture (MS+1.2Msucrose) for 30 min beforeplating on regrowth medium. Addition of mannitol to the pre-culturemedium improved survival of vitrified shoot tips. Direct dehydrationof pre-cultured shoot tips with concentrated PVS 2 was detrimentalto survival of vitrified shoot tips. Shoot tips pre-culturedon medium containing 0.3Msucrose plus 0.2Mmannitol, and loadedwith 20% PVS 2 for 30 min followed by 15 min incubation in 60%PVS 2 and 5 min incubation in 100% PVS 2 at 0 °C resultedin up to 54% survival after vitrification. About 50% of vitrifiedand warmed shoot tips formed shoots directly. Post-thaw culturingof vitrified shoot tips on medium containing an elevated levelof sucrose (0.2M) under diffuse light for the first week enhancedthe survival rate. Continuous culturing of vitrified shoot tipson high-sucrose medium induced multiple shoot formation.Copyright1998 Annals of Botany Company Solanum tuberosumL., potato, cryopreservation, germplasm conservation,in vitroconservation, meristems, shoot tips, tissue culture, vitrification. 相似文献
11.
12.
A reproducible method has been developed for the Biolistic transformationand regeneration of transgenic plants from embryogenic callusof rose (Rosa hybridaL.) cv. Glad Tidings. DNA delivery wasoptimized using the ß-glucuronidase (gus) gene. Thedistance between the stopping screen and target explants andsupplementation of pre-and post-bombardment culture media with0.25Mmyo-inositol influenced the transformation efficiency.Prior to culture on selection medium containing 250 mg l-1kanamycinsulphate, embryogenic calli were bombarded, using optimizedgene delivery parameters, with a plasmid carrying the neomycinphosphotransferase (nptII) gene. Somatic embryo-derived kanamycin-resistantplants were regenerated and subsequently transferred to glasshouseconditions. Transformation was confirmed by kanamycin resistanceof calli and plants, NPT II ELISA assay and Southern analysis.All transgenic plants were morphologically normal (true-to-type).Copyright1998 Annals of Botany Company Biolistic; genetic engineering; rose;Rosa hybridaL.; transformation. 相似文献
13.
Callus of sainfoin (Onobrychis viciifolia Scop.) was initiatedfrom stem and root explants which were obtained from seedlingsgrowing in vitro, on Linsmaier Skoog (LS) medium supplementedwith 1 mg l1 2, 4-D and 1 mg l1 BA or only 1 mgl1 BA, and the Vacin and Went medium without hormones.Somatic embryos were formed on LS medium containing 1 m l1BA. Embryos developed into complete plants on filter paper saturatedwith hormone-free LS medium. Onobrychis viciifolia, somatic embryogenesis, callus culture, plant regeneration 相似文献
14.
Michael E. Olson Daniel A. Todd Carolyn R. Schaeffer Alexandra E. Paharik Michael J. Van Dyke Henning Büttner Paul M. Dunman Holger Rohde Nadja B. Cech Paul D. Fey Alexander R. Horswill 《Journal of bacteriology》2014,196(19):3482-3493
Staphylococcus epidermidis is an opportunistic pathogen that is one of the leading causes of medical device infections. Global regulators like the agr quorum-sensing system in this pathogen have received a limited amount of attention, leaving important questions unanswered. There are three agr types in S. epidermidis strains, but only one of the autoinducing peptide (AIP) signals has been identified (AIP-I), and cross talk between agr systems has not been tested. We structurally characterized all three AIP types using mass spectrometry and discovered that the AIP-II and AIP-III signals are 12 residues in length, making them the largest staphylococcal AIPs identified to date. S. epidermidis
agr reporter strains were developed for each system, and we determined that cross-inhibitory interactions occur between the agr type I and II systems and between the agr type I and III systems. In contrast, no cross talk was observed between the type II and III systems. To further understand the outputs of the S. epidermidis
agr system, an RNAIII mutant was constructed, and microarray studies revealed that exoenzymes (Ecp protease and Geh lipase) and low-molecular-weight toxins were downregulated in the mutant. Follow-up analysis of Ecp confirmed the RNAIII is required to induce protease activity and that agr cross talk modulates Ecp activity in a manner that mirrors the agr reporter results. Finally, we demonstrated that the agr system enhances skin colonization by S. epidermidis using a porcine model. This work expands our knowledge of S. epidermidis
agr system function and will aid future studies on cell-cell communication in this important opportunistic pathogen. 相似文献
15.
The length of the seminal root (SR) axis and the number andlength of lateral roots (LRs) of sorghum (Sorghum bicolor Moench)were markedly inhibited by taro [Colocasia esculenta (L.) Schott]residues incorporated into a sand growing medium. The sand profilewas divided equally into zones with and without residues. Productionand elongation of the first-order LRs of the SR axis facingthe zone containing taro residues were severely suppressed.On the side facing the zone that was free of residues, productionand elongation of LRs was not inhibited. SR and LR growth wasdrastically impaired and many plants were killed when taro residueswere incorporated in large amounts into the uppermost 2 cm ofthe growing medium. The activity of the allelopathic substancesin the root zone appeared to be location-specific. Sorghum bicolor, seminal root, lateral root, Colocasia esculenta, taro, taro residues, allelopathic substances, root growth 相似文献
16.
The reproductive cycle of a population of Paxyodon
syrmatophorus(Meuschen, 1781), a mussel exploited for its shells
in the lowerTocantins River, Brazil, was studied between September
1997and August 1998. Monthly examination of gonad sections and
inspectionof the demibranchs of females showed that gametogenesis
takesplace all year round and that spawning occurs during the months
ofthe dry season. Gravid females were found throughout the period
betweenFebruary and September. Sexually mature mussels as small as
23mm in length were found and the smallest gravid female was 32mm in
length. The implications of the findings are discussedin relation to
the conservation and management of exploitedfreshwater mussel
populations in the region.
3 Author for correspondence. Telefax: +55-91-8251209. Email:
beasley{at}eletronet.com.br
4 Current address: UPIS, Sep/Sul EQ. 712/912 Conjunto "A" Brasília70390-125, DF Brazil (Received 20 September 1999; accepted 13 January 2000) 相似文献
17.
The catalytic and regulatory properties of phosphoenolpyruvate(PEP) carboxylase (PEPC) are modulated remarkably by the increasein the level of bicarbonate in the assay medium. The activityof PEPC increased by two-fold as the concentration of bicarbonatewas raised from 0.05 to 10 mM. During this state, there wasonly marginal effect on Km for PEP, while the affinity of PEPCto Mg2+ increased by >2 fold. In contrast, the sensitivityof PEPC to malate decreased with increasing concentration ofHCO3. Similarly, the stimulation by glucose 6-phosphate(G-6-P) at optimal concentration (10 mM) of HCO3 wasmuch less than that at suboptimal concentration (0.05 mM). K1for malate increased by about 3 fold and Ka for G-6-P risedby fourfold as bicarbonate concentration was rised from 0.05to 10 mM. These results suggest that HCO3 desensitizesPEPC to both malate and G-6-P. Further, these changes were manifestedin both dark- as well as light-forms of the enzyme. Similarresults were obtained with PEPC in leaf extracts or in purifiedform. We therefore propose that bicarbonate-induced changesare independent of phospho-rylation and possibly through a significantchange in the conformation of the enzyme. This is the firstdetailed report indicating marked modulation of regulatory andcatalytic properties of PEPC by bicarbonate, one of its substrate. (Received April 14, 1998; Accepted September 22, 1998) 相似文献
18.
Potassium, sodium and Chloride in the protoplasm of characeae 总被引:2,自引:0,他引:2
Using vacuolar perfusion, which enabled us to replace the cellsap with a solution containing no k+, Na+ and Cl, theconcentrations of these ions in the protoplasm of three speciesof fresh water Characeae were determined. They were respectively,78, 2 and 27 mM in Nitella flexilis, 101, 9 and 31 mM in Nitellapulchella, and 112, 3 and 21 mM in Chara australis. Our previouslyreported results (3) indicating that the chloroplast layer containedmuch more Na+ and Cl than the endoplasm has been questionedin the light of the present results.
1Present address: Department of Biology, College of GeneralEducation, Osaka University. (Received September 5, 1973; ) 相似文献
19.
A simple and efficient protocol is described for regeneration of wild sorghum (Sorghum dimidiatum) from cell suspension cultures. Fast-growing cell suspensions were established from shoot-meristem-derived callus. Plating
of the suspension on Murashige and Skoog agar medium supplemented with 2.5 mg l–1 2,4-dichlorophenoxyacetic acid (2,4-D) resulted in the formation of embryogenic calli. High-frequency (80%) somatic embryogenesis
from small cell clusters (300–400 μm) was observed when the cultures were initially maintained in liquid medium with reduced
levels of 2,4-D (0.25 mg l–1), followed by transfer to regeneration medium. Direct plating of these small clusters on regeneration medium or transfer
to liquid regeneration medium containing kinetin and 6-benzylaminopurine resulted in the development of mature somatic embryos
and plantlets. The regenerants developed to maturity and were all phenotypically and cytologically normal.
Received: 20 May 1998 / Revision received: 1 September 1998 / Accepted: 23 September 1998 相似文献
20.
Embryogenesis and Plantlet Formation through Direct Culture of Isolated Pollen of Nicotiana tabacum cv. Samsum and Nicotiana rustica cv. Rustica 总被引:1,自引:0,他引:1
Pollen embryos and plantlets of Nicotiana tabacum cv. Samsunand Nicotiana rustica cv. Rustica were obtained through directpollen culture without prior treatment or prior culture of anthersor buds. Isolated pollen was cultured first in a medium withoutsucrose, then transferred into Nitsch's H medium containing2% sucrose and 5 mM glutamine. The optimum medium for the initialculture was water and the optimum period of culture was ca.6 days when binucleate pollen was used.
1 Present address: Friedrich Miescher Inst., P.O.B. 273, CH-4002Basel, Switzerland. (Received January 18, 1982; Accepted March 19, 1982) 相似文献