ISSN:
1432-2048
Keywords:
Calcium (cytoplasmic free)
;
Chloroplast movement
;
Dye, calcium sensitive (Indo-1)
;
Light (blue, ultraviolet A)
;
Mougeotia
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The fluorescent calcium-sensitive dye 1-[2-amino-5-(6-carboxyindol-2-yl)-phenoxy]-2-(2′-amino-5′-methylphenoxy)-ethane-N,N,N′,N′-tetraacetic acid (indo-1) was loaded by a transplasmalemma pH gradient into filamentous cells and protoplasts of Mougeotia scalaris, such that most of the indo-1 fluorescence originated from the cytoplasm. Incubation of M. scalaris filaments in ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA)-buffered media (-log [Ca2+] (=pCa) 8 versus pCa 3) caused a consistent and significant decrease in the cytoplasmic free [Ca2+]. Pulses of the fluorescence excitation light (UV-A 365 nm, 0.7 s) caused an increase in cytoplasmic free [Ca2+] in M. scalaris that was nearly independent of the external [Ca2+] and of chloroplast dislocation by centrifugation. This calcium flux, highest in UV-A light, compared with blue or red light, probably resulted from a release of Ca2+ from intracellular stores. Increased cytoplasmic [Ca2+] may affect the velocity of chloroplast rotation since UV-A-light-mediated chloroplast movement was faster than in blue or red light. Consistently, the calcium ionophore A23187 and the calcium-channel agonist Bay-K8644 both increased the velocity of the red-light-mediated chloroplast rotation. Based on these and other observations, a Ca2+-induced decrease in cytoplasmic viscosity in Mougeotia is presumed to occur.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00208243
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