Cytokinin stimulates dihydropyridine-sensitive calcium uptake in moss protoplasts.
Cytokinin stimulates dihydropyridine-sensitive calcium uptake in moss protoplasts.
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细胞分裂素刺激苔藓原生质体中二氢吡啶敏感的钙吸收。
DOI：
10.1073/pnas.90.23.10937
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发表时间：
1993
影响因子：
11.1
通讯作者：
Gizinski,MJ
中科院分区：
文献类型：
--
作者：
Schumaker,KS;Gizinski,MJ
Ca2+ 通过二氢吡啶 (DHP) 敏感的 Ca2+ 通道流入被认为是苔藓原丝体细胞分裂素诱导芽形成的早期事件，因为 DHP 拮抗剂在细胞分裂素存在下抑制芽形成，而 DHP 激动剂在细胞分裂素不存在时刺激芽形成 [Conrad, P. A. & Helper, P. K. (1988) Plant Physiol. 86、684-687]。在本研究中，我们通过测量 45Ca2+ 流入苔藓原生质体来确定 DHP 敏感 Ca2+ 转运系统的存在。 Ca2+ 流入受到外部 KCl（高达 5 mM）的刺激，表明运输是电压依赖性的。 K(+) 诱导的 Ca2+ 内流对 DHP 敏感，在 500 nM 硝苯地平时抑制 > 50%。通过增加 DHP Ca2+ 通道激动剂 Bay K8644 的浓度来刺激 Ca2+ 流入，在 25 nM 时具有半最大效应；这种刺激只有在没有 K+ 的情况下才会出现，表明激动剂优先作用于极化膜。 Ca2+ 流入也受到苯烷基胺类药物（维拉帕米）和苯并硫氮卓类药物（地尔硫卓）的抑制。植物激素 6-苄氨基嘌呤持续刺激 Ca2+ 流入，Km 值为 1 nM，而腺嘌呤、吲哚乙酸和赤霉酸对 Ca2+ 转运没有影响。与 6-苄氨基嘌呤相比，细胞分裂素激动素和反式玉米素对 Ca2+ 流入产生更大的刺激，并诱导更多的芽形成。这些结果表明，Ca2+ 通过质膜上的电压依赖性 DHP 敏感 Ca2+ 通道被摄取到苔藓原生质体中，并且诱导芽形成的细胞分裂素效应之一是对该质膜 Ca2+ 通道的调节。
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. & Helper, 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 45Ca2+ 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 Km 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.