POLLEN-TUBE GROWTH IS COUPLED TO THE EXTRACELLULAR CALCIUM-ION FLUX AND THE INTRACELLULAR CALCIUM GRADIENT - EFFECT OF BAPTA-TYPE BUFFERS AND HYPERTONIC MEDIA
POLLEN-TUBE GROWTH IS COUPLED TO THE EXTRACELLULAR CALCIUM-ION FLUX AND THE INTRACELLULAR CALCIUM GRADIENT - EFFECT OF BAPTA-TYPE BUFFERS AND HYPERTONIC MEDIA
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DOI：
10.1105/tpc.6.12.1815
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发表时间：
1994-12-01
期刊：
影响因子：
11.6
通讯作者：
HEPLER, PK
中科院分区：
文献类型：
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作者：
PIERSON, ES;MILLER, DD;HEPLER, PK
百合花粉管具有陡峭的，尖端集中的细胞内Ca 2+梯度和尖端定向的细胞外Ca 2+内流。比率计量离子成像显示，梯度从顶端的3.0 μ M以上延伸到距离尖端20 μ m内的0.2 μ M，而应用Ca 2+特异性振动电极表明，测得的细胞外流入量在1.4和14 pmol cm（-2）sec（-1）之间。我们通过使用不同的1，2-双（邻氨基苯氧基）乙烷-N，N，N '，N'-四乙酸（BAPTA）型缓冲液和高渗培养基研究了这些现象之间的关系及其在管生长中的作用。注射活性BAPTA型缓冲液或应用高水平的蔗糖可逆地抑制生长，破坏细胞器的尖端带状化，并改变细胞质流动的正常模式。同时，这些治疗消散细胞内尖端聚焦梯度和细胞外Ca 2+通量。在BAPTA型缓冲剂中，5，5 '-二溴-BAPTA（解离常数[K-d]为1.5 μ M）和4，4 '-二氟-BAPTA（Kd为1.7 μ M）比具有更高亲和力的缓冲液表现出更大的活性（5，5 ′-二甲基-BAPTA，K-d为0.15 μ M; BAPTA，K-d为0.21 μ M; 5，5 ′-二氟-BAPTA，K-d为0.25 μ M）或对Ca 2+的较低亲和力（5-甲基，5 ′-硝基-BAPTA，K-d为22 μ M）。我们的研究结果提供的证据表明，不断增长的花粉管有开放的Ca 2+通道在其尖端，这些通道成为非生长管失活。蔗糖浓度升高的研究支持顶端质膜的伸展有助于维持Ca 2+信号的观点。
Lily pollen tubes possess a steep, tip-focused intracellular Ca2+ gradient and a tip-directed extracellular Ca2+ influx. Ratio-metric ion imaging revealed that the gradient extends from above 3.0 mu M at the apex to similar to 0.2 mu M within 20 mu m from the tip, while application of the Ca2+-specific vibrating electrode indicated that the extracellular influx measured between 1.4 and 14 pmol cm(-2) sec(-1). We examined the relationship between these phenomena and their role in tube growth by using different 1,2-bis(o-aminophenoxy)ethane N,N,N',N'-tetraacetic acid (BAPTA)-type buffers and hypertonic media, Injection of active BAPTA-type buffers or application of elevated levels of sucrose reversibly inhibited growth, destroyed tip zonation of organelles, and modified normal patterns of cytoplasmic streaming. Simultaneously, these treatments dissipated both the intracellular tip-focused gradient and the extracellular Ca2+ flux. Of the BAPTA-type buffers, 5,5'-dibromo-BAPTA (dissociation constant [K-d] is 1.5 mu M) and 4,4'-difluoro-BAPTA (K-d of 1.7 mu M) exhibited greater activity than those buffers with either a higher affinity (5,5'-dimethyl-BAPTA, K-d of 0.15 mu M; BAPTA, K-d of 0.21 mu M; 5,5'-difluoro-BAPTA, K-d of 0.25 mu M) or lower affinity (5-methyl, 5'-nitro-BAPTA, K-d of 22 mu M) for Ca2+. Our findings provide evidence that growing pollen tubes have open Ca2+ channels in their tip and that these channels become inactivated in nongrowing tubes. The studies with elevated sucrose support the view that stretching of the apical plasma membrane contributes to the maintenance of the Ca2+ signal.