Institute of Robotics and Intelligent Systems, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich, Switzerland.
Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland.
Lab Chip. 2017 Feb 14;17(4):671-680. doi: 10.1039/c6lc01307d.
Pollen tubes are tip-growing plant cells that deliver the sperm cells to the ovules for double fertilization of the egg cell and the endosperm. Various directional cues can trigger the reorientation of pollen tube growth direction on their passage through the female tissues. Among the external stimuli, protons serve an important, regulatory role in the control of pollen tube growth. The generation of local guidance cues has been challenging when investigating the mechanisms of perception and processing of such directional triggers in pollen tubes. Here, we developed and characterized a microelectrode device to generate a local proton gradient and proton flux through water electrolysis. We confirmed that the cytoplasmic pH of pollen tubes varied with environmental pH change. Depending on the position of the pollen tube tip relative to the proton gradient, we observed alterations in the growth behavior, such as bursting at the tip, change in growth direction, or complete growth arrest. Bursting and growth arrest support the hypothesis that changes in the extracellular H concentration may interfere with cell wall integrity and actin polymerization at the growing tip. A change in growth direction for some pollen tubes implies that they can perceive the local proton gradient and respond to it. We also showed that the growth rate is directly correlated with the extracellular pH in the tip region. Our microelectrode approach provides a simple method to generate protons and investigate their effect on plant cell growth.
花粉管是顶端生长的植物细胞，它们将精子细胞输送到胚珠中，进行卵子和胚乳的双受精。各种定向线索可以触发花粉管在穿过雌性组织时重新定向生长方向。在外部刺激中，质子在控制花粉管生长中起着重要的调节作用。在研究花粉管中对这种定向触发的感知和处理机制时，产生局部导向线索一直具有挑战性。在这里，我们开发并表征了一种微电极设备，通过水电解产生局部质子梯度和质子流。我们证实花粉管的细胞质 pH 值随环境 pH 值的变化而变化。根据花粉管尖端相对于质子梯度的位置，我们观察到生长行为的改变，例如尖端爆裂、生长方向改变或完全生长停滞。爆裂和生长停滞支持这样的假设，即细胞外 H 浓度的变化可能会干扰细胞壁的完整性和生长尖端处的肌动蛋白聚合。一些花粉管生长方向的改变意味着它们可以感知局部质子梯度并对其做出反应。我们还表明，生长速率与尖端区域的细胞外 pH 值直接相关。我们的微电极方法提供了一种简单的方法来产生质子并研究它们对植物细胞生长的影响。
