The liverwort Marchantia polymorpha operates a depolarization-activated Slowpoke (SLO) K+ channel that recognises pH changes in the environment
The liverwort Marchantia polymorpha operates a depolarization-activated Slowpoke (SLO) K+ channel that recognises pH changes in the environment
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DOI：
10.1101/2021.06.01.446568
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发表时间：
2021-06
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通讯作者：
F. Sussmilch;J. Böhm;G. Gessner;T. Maierhofer;T. Müller;S. Heinemann;D. Becker;R. Hedrich
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作者：
F. Sussmilch;J. Böhm;G. Gessner;T. Maierhofer;T. Müller;S. Heinemann;D. Becker;R. Hedrich
电压依赖性离子通道是细胞兴奋性和电通信的先决条件-多细胞生物在多变的陆地环境中茁壮成长的重要特征。基于它们存在于现存的胚胎植物和密切相关的绿色藻类中，第一批在陆地上生存的植物可能具有编码与大电导钙激活K+通道（来自Slo家族的BK通道）同源的通道的基因，以及来自植物VG型家族的初级电压门控钾通道（Shaker或Kv通道）。虽然Shaker通道的功能和门控已经在开花植物中得到表征，但到目前为止，BK通道的知识仅限于动物模型。在人类中，BK介导的K+外排在精子运动和膜极化中具有关键作用，以实现受精。在地钱中，MpBK 2a通道基因在雄性生殖组织中表达最高，表明这些通道可能在有性生殖中起作用。我们的特点MpBK 2a通道，并发现他们是强烈的K+选择性，外向整流，80 pS的通道，能够复极化后的膜刺激依赖性去极化。与其动物对应物相反，MpBK 2a对细胞质Ca 2+变化不敏感，但有效地通过pH变化门控。考虑到这种植物BK通道即使在痕量的外部K+存在下和在低pH值下也是活跃的，地钱通道可以在应激的史前条件下稳定膜电位，包括早期植物先驱征服土地时的营养耗尽和酸性环境。
Voltage-dependent ion channels are a prerequisite for cellular excitability and electrical communication – important traits for multicellular organisms to thrive in a changeable terrestrial environment. Based on their presence in extant embryophytes and closely-related green algae, the first plants to survive on land likely possessed genes encoding channels with homology to large-conductance calcium-activated K+ channels (BK channels from the Slo family) in addition to primary voltage-gated potassium channels from the plant VG-type family (Shaker or Kv channels). While the function and gating of Shaker channels has been characterised in flowering plants, so far knowledge of BK channels has been limited to animal models. In humans, BK-mediated K+ efflux has a critical role in sperm motility and membrane polarisation to enable fertilisation. In the liverwort Marchantia polymorpha, the MpBK2a channel gene is most highly expressed in male reproductive tissue, suggesting that these channels may function in sexual reproduction. We characterised MpBK2a channels and found them to be strongly K+-selective, outward-rectifying, 80-pS channels capable of repolarising the membrane after stimulus-dependent depolarisation. In contrast to its animal counterpart, MpBK2a is insensitive to cytoplasmic Ca2+ variations but effectively gated by pH changes. Given that this plant BK channel is active even in the presence of trace amounts of external K+ and at low pH, the liverwort channel could have stabilised the membrane potential under stressful pre-historic conditions including nutrient-depleted and acid environments as early plant pioneers conquered land.