Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Würzburg, Germany.
Center for Computational and Theoretical Biology, University of Würzburg, Würzburg, Germany.
PLoS Biol. 2020 Dec 9;18(12):e3000964. doi: 10.1371/journal.pbio.3000964. eCollection 2020 Dec.
The carnivorous plant Dionaea muscipula harbors multicellular trigger hairs designed to sense mechanical stimuli upon contact with animal prey. At the base of the trigger hair, mechanosensation is transduced into an all-or-nothing action potential (AP) that spreads all over the trap, ultimately leading to trap closure and prey capture. To reveal the molecular basis for the unique functional repertoire of this mechanoresponsive plant structure, we determined the transcriptome of D. muscipula's trigger hair. Among the genes that were found to be highly specific to the trigger hair, the Shaker-type channel KDM1 was electrophysiologically characterized as a hyperpolarization- and acid-activated K+-selective channel, thus allowing the reuptake of K+ ions into the trigger hair's sensory cells during the hyperpolarization phase of the AP. During trap development, the increased electrical excitability of the trigger hair is associated with the transcriptional induction of KDM1. Conversely, when KDM1 is blocked by Cs+ in adult traps, the initiation of APs in response to trigger hair deflection is reduced, and trap closure is suppressed. KDM1 thus plays a dominant role in K+ homeostasis in the context of AP and turgor formation underlying the mechanosensation of trigger hair cells and thus D. muscipula's hapto-electric signaling.
捕蝇草的多细胞触发毛可以感知与动物猎物接触时的机械刺激，它是一种肉食性植物。在触发毛的基部，机械刺激被转化为全有或全无的动作电位 (AP)，这种动作电位会传遍整个陷阱，最终导致陷阱关闭并捕获猎物。为了揭示这种机械响应植物结构独特功能的分子基础，我们测定了捕蝇草触发毛的转录组。在发现的高度特异于触发毛的基因中，Shaker 型通道 KDM1 被电生理学鉴定为超极化和酸激活的 K+选择性通道，从而允许在 AP 的超极化阶段将 K+离子重新摄取到触发毛的感觉细胞中。在陷阱发育过程中，触发毛的电兴奋性增加与 KDM1 的转录诱导有关。相反，当成年陷阱中的 Cs+阻断 KDM1 时，触发毛偏转引起的 AP 起始减少，陷阱关闭受到抑制。因此，KDM1 在 AP 形成和触发毛细胞机械感觉下膨压形成的 K+动态平衡中起主导作用，从而也在捕蝇草的触电信号中起主导作用。
