Ionic mechanism and role of phytochrome-mediated membrane depolarisation in caulonemal side branch initial formation in the moss Physcomitrella patens
Ionic mechanism and role of phytochrome-mediated membrane depolarisation in caulonemal side branch initial formation in the moss Physcomitrella patens
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DOI：
10.1007/bf01007695
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发表时间：
1997-02-01
期刊：
影响因子：
4.3
通讯作者：
Johannes, E
中科院分区：
文献类型：
--
作者：
Ermolayeva, E;Sanders, D;Johannes, E
在青苔（Physcomitrella patens, Hedw.）的茎状细丝中，红光触发光敏色素介导的质膜瞬时去极化和侧枝首枝的形成。采用三电极电压钳和离子通量测量来阐明红光诱导离子输运变化的离子机制和生理相关性。电流-电压分析表明，可渗透到K+和Ca2+的离子通道在去极化的峰值被激活。红光引起的钙内流与各种条件下的去极化一致，表明电压门控Ca2+通道的参与。各自的K+通量表现为小的初始内流，随后是剧烈的瞬态外流。红光照射后Cl-外排也增加，说明阴离子通道在去极化电流中的作用。在四乙基铵（10 mM）或尼氟酸（1 μ M）的存在下，它们阻断了红光诱导的膜去极化和离子通量，红光促进的侧支首字母的形成也被消除了。镧（100亩M）抑制K+通量和部分红光激活的Ca2+初始内流，使侧枝首字母在红光下的发育减少50%。结果表明，红光诱导的离子通量与生理反应之间存在因果关系。根据信号传导过程中质膜上离子通道相互作用的新模型，讨论了红灯触发膜电位瞬态的事件序列和离子传输在刺激-响应耦合中的作用。
In caulonemal filaments of the moss Physcomitrella patens (Hedw.), red light triggers a phytochrome-mediated transient depolarisation of the plasma membrane and the formation of side branch initials. Three-electrode voltage clamp and ion flux measurements were employed to elucidate the ionic mechanism and physiological relevance of the red-light-induced changes in ion transport. Current-voltage analyses indicated that ion channels permeable to K+ and Ca2+ are activated at the peak of the depolarisation. Calcium influx evoked by red light coincided with the depolarisation in various conditions, suggesting the involvement of voltage-gated Ca2+ channels. Respective K+ fluxes showed a small initial influx followed by a dramatic transient efflux. A role of anion channels in the depolarising current is suggested by the finding that Cl- efflux was also increased after red light irradiation. In the presence of tetraethylammonium (10 mM) or niflumic acid (1 mu M), which block the red-light-induced membrane depolarisation and ion fluxes, the red-light-promoted formation of side branch initials was also abolished. Lanthanum (100 mu M), which inhibits K+ fluxes and part of the initial Ca2+ influx activated by red light, reduced the development of side branch initials in red light by 50%. The results suggest a causal link between the red-light-induced ion fluxes and the physiological response. The sequence of events underlying the red-light-triggered membrane potential transient and the role of ion transport in stimulus-response coupling are discussed in terms of a new model for ion-channel interaction at the plasma membrane during signalling.