Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Functional analysis of the eyespot in Chlamydomonas reinhardtii mutant ey 627, mt − (1992)
    Springer
    Planta 188 (1992), S. 513-521 
    Details
    ISSN: 1432-2048
    Keywords: Chlamydomonas ; Confocal laser scanning microscopy ; Eyespot ; Photoreceptor potential ; Phototaxis ; Retinal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The function of the eyespot in phototaxis of the flagellate green alga Chlamydomonas reinhardtii Dangeard was studied using quantitative reflection confocal laser scanning microscopy and photoelectric measurements. The reflective properties of the eyespot and the photoreceptor current of the C. reinhardtii eyespot mutant ey 627, mt − were compared with those of Chlamydomonas strains possessing a well-developed eyespot. Under growth conditions in which strongly disorganized eyespots were observed in the mutant by electron microscopy, there was a significant reduction in the reflection intensity of the eyespot and in the amplitude ratio (500∶440 nm) of photoreceptor currents induced by flashes of 500- and 440-nm light in non-oriented cells. Photoelectrical responses of pre-oriented cells revealed that the latter effect is caused by an altered directional sensitivity of the antenna complex, whereas the functional state of the photoreceptor pigment is not strongly affected in mutant cells. Both the reflection intensity and the amplitude ratio of photoreceptor currents increased to the level of reference strains under conditions supporting the development of a well-organized eyespot in the mutant. Furthermore, incubation of the mutant with high concentrations of all-trans-retinal (10 μM), independent of whether carotenoid biosynthesis was inhibited or not, was found to increase the reflection intensity of the eyespot. An increase in the rate of photoorientation of the mutant occurred concomitant with the increase in the reflective properties of the mutant eyespot. These observations demonstrate the importance of an intact eyespot for interference reflection and absorption of phototactically active light, and thus for the directional sensitivity of the eyespot apparatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197043
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Calcium modulates rapid protein phosphorylation/dephosphorylation in isolated eyespot apparatuses of the green alga Spermatozopsis similis (1995)
    Springer
    Planta 197 (1995), S. 343-351 
    Details
    ISSN: 1432-2048
    Keywords: Calcium ; dependent protein phosphorylation ; Eyespot apparatus ; Phototaxis ; Protein kinase ; Protein phosphatase ; Spermatozopsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present an initial characterization of protein kinase and phosphatase activities associated with isolated eyespot apparatuses, the organelle involved in blue/ green-light-mediated behavioural responses of flagellate green algae. In the presence of the phosphatase inhibitors okadaic acid and vanadate, rapid overall protein phosphorylation (t0.5 ≈ 10 s) was observed. The majority of protein kinase activities and their substrates were identified as integral or tightly-bound peripheral membrane proteins. While vanadate generally increased the phosphate incorporation into all phosphoproteins, okadaic acid specifically enhanced phosphorylation of proteins in the range of 39–43 kDa. In contrast to all other phosphoproteins in this subcellular fraction, two proteins with apparent molecular masses of 83 and 16 kDa shared remarkable similarities: (i) They exhibited a fast turnover of the 32P-label, even in the presence of phosphatase inhibitors, and (ii) their dephosphorylation was delayed at 10−8 M free Ca2+. In addition, the 16-kDa protein underwent thiophosphorylation. The general in-vitro phosphorylation pattern was strongly influenced by alterations of free Ca2+ in a concentration range known to affect responses related to phototactic and photophobic behaviour of this alga (10−8 M to 10−7 M). However, characteristics of Ca2+-calmodulin-dependent protein kinases were not observed, i.e. exogenous calmodulin and trifluoperazine had no significant effect on protein phosphorylation. Also exogenous lipids (phosphatidylserine, diacylglycerol), inhibitors of cGMP and cAMPdependent protein kinases and protein kinase C (H-7 and HA1004) as well as exogenously added cGMP and cAMP did not potentiate or inhibit protein phosphorylation. These characteristics of the kinase activity in our fraction most closely resemble those of the plant- and protist-specific group of Ca2+-dependent, calmodulin-independent protein kinases. In-situ phosphorylation experiments following electrophoretic separation revealed the presence of three putative Ca2+-dependent kinases or their catalytic subunits (77,48 and 47 kDa) in the eyespot preparation. In addition, a Ca2+-independent activity at 28 kDa was detected. Possible roles of reversible protein phosphorylation in eyespot apparatuses are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202656
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Spinach ferredoxin is a calcium-binding protein (1987)
    Springer
    Planta 171 (1987), S. 565-568 
    Details
    ISSN: 1432-2048
    Keywords: Calcium binding ; Ferredoxin (Ca2+-binding) ; Spinacia (Ca2+ binding) ; “Stains-all” (Ca2+ binding)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spinach-leaf ferredoxin was identified as a calcium-binding protein by 45Ca autoradiography on nitrocellulose membranes and with the cationic carbocyanine dye 1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl] naphtho[1,2-d]thiazolium bromide (“stains-all”). Binding of 45Ca was observed at pH 6.8 and pH 7.8 and in the presence of 5 mM and 20 mM MgCl2. At the higher MgCl2 concentration the Ca2+-binding capacity is reduced. Only micromolar concentrations of LaCl3, however, are required to achieve a similar effect. Both the oxidized and reduced forms of ferredoxin bind calcium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392307
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Calcium binding by spinach stromal proteins (1987)
    Springer
    Planta 171 (1987), S. 259-265 
    Details
    ISSN: 1432-2048
    Keywords: Calcium (binding proteins) ; Chloroplast (stroma) ; Ionic regulation ; Photosynthesis ; Spinacia (calcium binding)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Calcium binding to spinach (Spinacia oleracea L.) stromal proteins was examined by dual-wavelength spectrophotometry using the metallochromic indicator tetramethylmurexide. The data are consistent with the existence of at least two, probably independent, classes of binding sites. The total number of binding sites varied between 90–155 nmol·mg−1 protein with “average” binding constants of 1.1–2.7·mM−1. Both Mg2+ and La3+ inhibited calcium binding competitively, with “average” inhibitor constants of 0.26·mM−1 and 39.4·mM−1, respectively; an increase in the potassium concentration up to 50 mM had no effect. In a typical experiment a decrease in pH (7.8 to 7.1) resulted in a decrease in the total number of calcium binding sites from 90 to 59 nmol·mg−1 protein, but in an increase of the “average” affinity from 2.7 to 4.5·mM−1. Calculations, using these data and those of Gross and Hess (1974, Biochim. Biophys. Acta 339, 334–346) for binding site I of washed thylakoid membranes, showed that the free-Ca2+ concentration in the stroma under dark conditions, pH 7.1, is higher than under light conditions, pH 7.8. The physiological relevance of the observed calcium binding by stromal proteins is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391103
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Carotenoids in the eyespot apparatus of the flagellate green alga Spermatozopsis similis: Adaptation to the retinal-based photoreceptor (1994)
    Springer
    Planta 193 (1994), S. 38-43 
    Details
    ISSN: 1432-2048
    Keywords: Carotenoid ; Eyespot apparatus ; Green algae ; Phototaxis ; Photoreceptor screen ; Spermatozopsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolated intact eyespot apparatuses, the photoreceptive organelles involved in blue-light-mediated photoresponses of flagellate green algae, were analyzed regarding their carotenoid composition. Carotenoids from the eyespot apparatuses of Spermatozopsis similis were identified by high-performance liquid chromatography, visible-light absorption spectra, mass spectroscopy and by 1H-nuclear magnetic resonance spectroscopy (carotenes), and compared with those of whole-cell extracts. Both extracts contained β,β-carotene, β,ψ-carotene (formerly γ-carotene), lycopene, lutein, zeaxanthin, violaxanthin and all-E-and 9′-Z-neoxanthin. The relative carotenoid compositions, however, differed significantly. A twofold relative increase in the total carotene level was evident in the fraction enriched in eyespot apparatuses. This was mainly due to an increase in the monocyclic β,ψ-carotene and the aliphatic lycopene, whereas the relative content of β,β-carotene remained unchanged. On the other hand a relative decrease in the total xanthophyll content, especially of lutein and the epoxidic carotenoid neoxanthin, was observed in the eyespot apparatuses compared with the whole-cell extracts. The decrease of the latter resulted almost solely from a reduction of the 9′-Z-rather than the all-E-isomer. The bulk of the carotenes is thought to be localized in the highly organized eyespot lipid globules, which act as a combined quarter-wave interference reflector and absorption screen for the photoreceptor in green algae. The enrichment of β,ψ-carotene and lycopene in the eyespot apparatuses, extending the range of visible light absorption to longer wavelengths, represents an adaptation of the screen to the retinal-based photoreceptor of flagellate green algae and is one of the prerequisites for maximal directional sensitivity of the eyespot apparatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191604
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Two members of the ERabp gene family are expressed differentially in reproductive organs but to similar levels in the coleoptile of maize (1993)
    Springer
    Plant molecular biology 23 (1993), S. 57-66 
    Details
    ISSN: 1573-5028
    Keywords: auxin ; auxin-binding protein ; auxin receptor ; ERabp gene ; differential expression ; maize (Zea mays L.) ; in situ hybridization ; confocal laser scanning microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A Zea mays cDNA clone, ZmERabp4, coding for a new member of the auxin-binding protein family was isolated. The primary amino acid sequence contains an N-terminal hydrophobic leader sequence, a potential glycosylation site (Asn136-Thr-Thr) and a C-terminal KDEL motif known to be responsible for retention of proteins within the lumen of the ER. The expression pattern of the ZmERabp4 gene in various organs of maize differs from the expression pattern previously observed for the ZmERabp1 gene. The ZmERabp4 gene is expressed highly in male flower organs, whereas the ZmERabp1 gene shows highest expression in female flower parts. In situ hybridization and analysis by laser scanning microscopy revealed enhanced levels of expression for both genes in the coleoptile when compared with the primary leaf of etiolated maize seedlings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021419
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Novel touch-induced, Ca2+-dependent phobic response in a flagellate green alga (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 97-109 
    Details
    ISSN: 0886-1544
    Keywords: calcium ; flagellar movement ; mechanotransduction ; mechanoshock response ; Spermatozopsis similis ; video analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The biflagellate green alga Spermatozopsis similis exhibits a remarkable avoidance reaction in addition to the photophobic or stop response characteristic of such algae. S. similis normally swims forward with its anteriorly attached flagella directed posteriorly and propagating sine-like waves from base to tip. Upon contact with surfaces or other cells, S. similis responds with rapid backward swimming, covering distances of up to 50 μm in 140 to 220 msec. This reaction, which we term the mechanoshock response, also can be triggered by vigorous mechanical stimulation, but not by physiological light intensities. It consists of 3 phases: (1) a rapid acceleration phase with average duration of 31 msec; (2) a phase of about 66 msec with constant high speed (maximal velocities of 〉 600 μm·sec-1) or slow deceleration; and (3) a deceleration phase of ∼ 83 msec, followed by a stop or short period of circling. The cells then resume forward swimming in a random direction. Prior to the mechanoshock response the flagella rapidly are brought together into a close parallel configuration extending anteriorly of the cell body. They then appear to propel the cell by undulatory beating, while the cell describes a pronounced helical path. Small decreases in the extracellular Ca2+ concentration, as well as low concentrations of Ba2+, strongly suppress the probability of this phobic reaction. We conclude that this mechanoshock response involves large Ca2+ influxes, probably mediated by mechanosensitive and/or stretch-activated ion-channel(s). © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970290202
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...