ISSN:
1615-6102
Keywords:
Auxin
;
Maize coleoptiles
;
Membrane potential
;
Cycloheximide
;
Protein synthesis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary The contribution of protein synthesis and secretion to indol acetic acid (IAA) induced polarisation of the plasma membrane voltage (V M) was investigated. TheV M of coleoptiles fromZea mays was measured in the presence of known inhibitors of protein- and RNA synthesis, as well as those of Golgi-mediated vesicle secretion. Inhibitors were applied under conditions at which they are known to abolish IAA stimulated H+ secretion and cell elongation effectively. Cycloheximide (CHI), an inhibitor of protein synthesis, caused depolarisation ofV M with a half maximal concentration of approximately 20 μM. At 100 μM CHI,V M depolarised to a new stable voltage with a half time of 9.8 ± 0.6 min. The temporal similarity of CHI-induced depolarisation and cessation of coleoptile elongation suggests that the induced change inV M underlies inhibition of elongation. CHI evoked membrane depolarisation to a final voltage of about −100 mV irrespective of the presence or absence of auxin in the external medium. Thus, CHI probably affected constitutive membrane transport properties independently of IAA-induced modulation of transport proteins. Cordycepin (COR), an inhibitor of RNA synthesis, had no significant effect at 400 μM onV M of IAA-treated cells, suggesting that gene transcription for transport- or regulatory protein synthesis was not essential for IAA-generated polarisation ofV M. Brefeldin-A (BFA), an inhibitor of Golgi-mediated vesicle secretion in maize coleoptiles, had no perceivable effect at 20 mg/1 onV M of IAA-treated coleoptile cells, demonstrating that constitutive or IAA-stimulated protein secretion was not essential for the mechanism underlying IAA-evokedV M polarisation. Hence, IAA-stimulated and COR/BFA-depressed H+ extrusion in elongating coleoptiles may not be entirely mediated by auxin-enhanced ATPase activity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01288027
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