ISSN:
1432-2048
Keywords:
ATPase
;
Auxin
;
Cucurbita
;
Hypocotyl
;
Membrane fractionation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Membrane fractions from Cucurbita maxima hypocotyls were isolated in a medium which inhibits the action of endogenous phospholipases. After removal of soluble phosphatases by Sepharose 2B-CL column chromatography, an auxin-stimulated ATPase activity was found in membrane fractions from linear sucrose gradients. In the presence of 10-4 M phenylacetic acid (PAA), the stimulation by indol-3-acetic acid (IAA) exhibited a bimodal concentration dependence with maximal stimulation of about 50% at 10-6 M IAA. Without PAA, only a high concentration of 10-4 M IAA was stimulatory, whereas 10-6 M IAA had no apparent effect and 10-8 M IAA exhibited weak inhibition. PAA alone had only weak or no effects. The effects of IAA must be considered as hormone-specific. The ATPase activity in the presence of 10-4 M PAA was activated only by 2,4-dichlorophenoxyacetic acid (2,4-D), an active auxin analogue, but not by the inactive stereoisomers, 2,3-D and 3,5-D. Comparison with marker enzyme profiles suggested that part of the auxin-stimulated ATPase was localized on plasma membranes as well as other compartments. Thus, the auxin-stimulated ATPase may become a useful tool in the investigation of the mechanism of action of auxin.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00386536
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