ISSN:
1432-072X
Keywords:
Amplification
;
Blue-green algae
;
Cations
;
Gating channels
;
Ionophores
;
Phobic response
;
Phormidium uncinatum
;
Photomovement
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The sensory transduction chain of photophobic responses in the blue-green alga, Phormidium uncinatum seems to involve a gating cation transport through membrane bound ion channels which provides an effective amplification. The calcium conducting ionophore A23187 inhibits the photophobic response totally and induces frequent reversals which resemble phobic responses but occur without any light stimulation. This indicates that the electrogenic ion conductance may depend on a gradient of divalent cations, esp. calcium. The calcium conductance during a photophobic response is further confirmed by the inhibitory effect of ruthenium red and lanthanum, blockers of the electrogenic calcium transport. In the case of lanthanum this inhibition is found at a concentration at which neither the number of motile filaments nor the average speed of movement is impaired. Incorporation of ionophores for monovalent cations (gramicidin and valinomycin) only partially impairs the response. Similarly, inhibition of the Na+/K+ pump by ouabain is less effective. Thus, the existence of a countercurrent of monovalent cations during the response, which has been described for e.g. ciliates, is yet obscure in blue-green algae.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00451502
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