Department of Biology Area 9, University of York, York YO10 5DD, UK.
New Phytol. 2011 Jul;191(1):84-91. doi: 10.1111/j.1469-8137.2011.03664.x. Epub 2011 Mar 3.
• Plant two-pore K(+) channels (TPKs) have been shown previously to play a role in vacuolar K(+) homeostasis. TPK activity is insensitive to membrane voltage, but regulated by cytoplasmic calcium and 14-3-3 proteins. This study reports that membrane stretch and osmotic gradients also alter the activity of TPKs from Arabidopsis, rice and barley, and that this may have a physiological relevance for osmotic homeostasis. • Mechanosensitivity was studied using patch clamp experiments and TPKs from Arabidopsis, rice and barley. In addition, the capability of TPKs to act as osmosensors was determined. By using protoplast disruption assays and intact plant survival assays, in genotypes that differed in TPK expression, the physiological relevance of TPK-based osmosensing was tested. • TPKs from all three species showed varying degrees of mechanosensitivity. TPK activity in channels from all three species was sensitive to trans-tonoplast osmotic gradients. TPK osmosensing is likely to proceed via the detection of small perturbations in membrane tension. Intact plant and protoplast assays showed that TPK-based osmosensing is important during exposure to rapid changes in external osmolarity. • Vacuolar TPK channels can act as intracellular osmosensors and rapidly increase channel activity during hypo-osmotic shock to release vacuolar K(+) .
• 先前已证实植物双孔钾（2P）通道（TPK）在液泡钾稳态中发挥作用。TPK 活性对膜电压不敏感，但受细胞质钙和 14-3-3 蛋白调节。本研究报告称，膜拉伸和渗透梯度也会改变来自拟南芥、水稻和大麦的 TPK 的活性，这对于渗透稳态可能具有生理相关性。 • 使用膜片钳实验和来自拟南芥、水稻和大麦的 TPK 研究了机械敏感性。此外，还确定了 TPK 作为渗透传感器的能力。通过使用原生质体破坏测定和完整植物存活测定，在 TPK 表达不同的基因型中，测试了基于 TPK 的渗透感应的生理相关性。 • 来自所有三种物种的 TPK 均显示出不同程度的机械敏感性。来自所有三种物种的通道中的 TPK 活性对跨液泡渗透梯度敏感。TPK 渗透感应可能通过检测膜张力的微小波动来进行。完整植物和原生质体测定表明，在暴露于外部渗透压快速变化时，基于 TPK 的渗透感应很重要。 • 液泡 TPK 通道可以作为细胞内渗透传感器，在低渗冲击期间迅速增加通道活性以释放液泡钾（K+）。
