Katicheva Lyubov, Sukhov Vladimir, Akinchits Elena, Vodeneev Vladimir
Department of Biophysics, Lobachevsky State University of Nizhni Novgorod, Gagarina Av., 23, Nizhni Novgorod, Russia.
Department of Biophysics, Lobachevsky State University of Nizhni Novgorod, Gagarina Av., 23, Nizhni Novgorod, Russia
Plant Cell Physiol. 2014 Aug;55(8):1511-9. doi: 10.1093/pcp/pcu082. Epub 2014 Jun 12.
Variation potential (VP) in higher plants cells is a transitory depolarization of the plasma membrane occurring in response to external damage. The effects of VP on different physiological processes are actively studied, but little is known about their ionic nature, which limits the interpretation of VP-induced functional changes. It is thought that VP generation is based on transient inactivation of plasma membrane proton pumps and is not connected to passive ionic fluxes. To study burn-induced VP in wheat seedlings, we measured membrane electric potential and cell input resistance. Cell input resistance decreased during VP generation, indicating that ionic channels were activated. In addition, VP amplitude decreased when the extracellular calcium concentration was lowered. When anion channels were blocked by ethacrynic acid addition, the VP had poor depolarization speed and amplitude. A decrease in the chlorine gradient by extracellular chlorine concentration shift leads to lowering of the VP amplitude and depolarization speed. This result indicates the role of chlorine efflux in depolarization phase formation. The VP repolarization is connected to potassium ion efflux, that is confirmed by repolarization suppression under addition of the potassium channel blocker tetraethylammonium (TEA) and an increase in the extracellular potassium concentration. We also showed that the addition of a proton pump inhibitor leads to membrane potential depolarization and inhibition of VP generation. These results suggest that the VP may be formed not only by transient suppression of proton pumps but also by passive ionic fluxes through the membrane.
高等植物细胞中的变异电位（VP）是质膜的一种瞬时去极化现象，它是对外部损伤的响应而产生的。人们正在积极研究VP对不同生理过程的影响，但对其离子性质了解甚少，这限制了对VP诱导的功能变化的解释。据认为，VP的产生基于质膜质子泵的瞬时失活，且与被动离子通量无关。为了研究小麦幼苗中烧伤诱导的VP，我们测量了膜电位和细胞输入电阻。在VP产生过程中细胞输入电阻降低，这表明离子通道被激活。此外，当细胞外钙浓度降低时，VP幅度减小。当通过添加依他尼酸阻断阴离子通道时，VP的去极化速度和幅度都很差。细胞外氯浓度变化导致氯梯度降低，从而使VP幅度和去极化速度降低。这一结果表明氯外流在去极化相形成中的作用。VP的复极化与钾离子外流有关，这在添加钾通道阻滞剂四乙铵（TEA）后复极化受到抑制以及细胞外钾浓度增加时得到了证实。我们还表明，添加质子泵抑制剂会导致膜电位去极化并抑制VP的产生。这些结果表明，VP可能不仅由质子泵的瞬时抑制形成，还由通过膜的被动离子通量形成。
