CYTOKININ STIMULATES DIHYDROPYRIDINE-SENSITIVE CALCIUM-UPTAKE IN MOSS PROTOPLASTS

被引:51
作者
SCHUMAKER, KS
GIZINSKI, MJ
机构
[1] Department of Plant Sciences, University of Arizona, Tucson
关键词
SIGNAL TRANSDUCTION; PLANT ION CHANNEL; PHYTOHORMONE; BUD FORMATION; PHYSCOMITRELLA-PATENS;
D O I
10.1073/pnas.90.23.10937
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Ca2+ influx through dihydropyridine (DHP)-sensitive Ca2+ channels is thought to be an early event in cytokinin-induced bud formation in moss protonema because DHP antagonists inhibit bud formation in the presence of cytokinin and DHP agonists stimulate bud formation in the absence of cytokinin [Conrad, P. A. & Hepler, P. K. (1988) Plant Physiol. 86, 684-687]. In the present study, we established the presence of a DHP-sensitive Ca2+ transport system by measuring Ca-45(2+) influx into moss protoplasts. Ca2+ influx was stimulated by external KCl (up to 5 mM), indicating that transport is voltage-dependent. K+-induced Ca2+ influx was DHP-sensitive with >50% inhibition at 500 nM nifedipine. Ca2+ influx was stimulated by increasing concentrations of the DHP Ca2+ channel agonist Bay K8644 with half-maximal effects at 25 nM; this stimulation was seen only in the absence of K+, suggesting that the agonist works preferentially on polarized membranes. Ca2+ influx was also inhibited by phenylalkylamines (verapamil) and benzothiazepines (diltiazem). The phytohormone 6-benzylaminopurine consistently stimulated Ca2+ influx with a K(m) value of 1 nM, whereas adenine, indoleacetic acid, and gibberellic acid had no effect on Ca2+ transport. The cytokinins kinetin and trans-zeatin caused a greater stimulation of Ca2+ influx and induced more bud formation than did 6-benzylaminopurine. These results indicate that Ca2+ is taken up into moss protoplasts through voltage-dependent DHP-sensitive Ca2+ channels on the plasma membrane and that one of the cytokinin effects in the induction of bud formation is regulation of this plasma membrane Ca2+ channel.
引用
收藏
页码:10937 / 10941
页数:5
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