Böhm J, Scherzer S, Shabala S, Krol E, Neher E, Mueller T D, Hedrich R
Julius-von-Sachs Institute, Department for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany.
School of Land and Food, University of Tasmania, Hobart TAS 7001, Australia.
Mol Plant. 2016 Mar 7;9(3):428-436. doi: 10.1016/j.molp.2015.09.017. Epub 2015 Oct 9.
The animal diet of the carnivorous Venus flytrap, Dionaea muscipula, contains a sodium load that enters the capture organ via an HKT1-type sodium channel, expressed in special epithelia cells on the inner trap lobe surface. DmHKT1 expression and sodium uptake activity is induced upon prey contact. Here, we analyzed the HKT1 properties required for prey sodium osmolyte management of carnivorous Dionaea. Analyses were based on homology modeling, generation of model-derived point mutants, and their functional testing in Xenopus oocytes. We showed that the wild-type HKT1 and its Na(+)- and K(+)-permeable mutants function as ion channels rather than K(+) transporters driven by proton or sodium gradients. These structural and biophysical features of a high-capacity, Na(+)-selective ion channel enable Dionaea glands to manage prey-derived sodium loads without confounding the action potential-based information management of the flytrap.
肉食性捕蝇草（茅膏菜科捕蝇草属）的动物类食物含有钠负荷，该钠负荷通过一种HKT1型钠通道进入捕虫器，该通道在捕虫器内叶表面的特殊上皮细胞中表达。猎物接触后会诱导DmHKT1的表达和钠摄取活性。在此，我们分析了肉食性捕蝇草在猎物钠溶质管理方面所需的HKT1特性。分析基于同源建模、模型衍生点突变体的生成及其在非洲爪蟾卵母细胞中的功能测试。我们表明，野生型HKT1及其钠钾通透突变体作为离子通道发挥作用，而非由质子或钠梯度驱动的钾转运体。这种高容量、钠选择性离子通道的结构和生物物理特性使捕蝇草的腺体能够管理猎物来源的钠负荷，而不会干扰捕蝇草基于动作电位的信息管理。
