Division of Biological Science, Graduate School of Science, Nagoya University, Aichi, Nagoya, Japan.
Plant Physiol. 2012 Jun;159(2):826-34. doi: 10.1104/pp.112.195537. Epub 2012 Apr 11.
The plasma membrane H(+)-ATPase generates an electrochemical gradient of H(+) across the plasma membrane that provides the driving force for solute transport and regulates pH homeostasis and membrane potential in plant cells. Recent studies have demonstrated that phosphorylation of the penultimate threonine in H(+)-ATPase and subsequent binding of a 14-3-3 protein is the major common activation mechanism for H(+)-ATPase in vascular plants. However, there is very little information on the plasma membrane H(+)-ATPase in nonvascular plant bryophytes. Here, we show that the liverwort Marchantia polymorpha, which is the most basal lineage of extant land plants, expresses both the penultimate threonine-containing H(+)-ATPase (pT H(+)-ATPase) and non-penultimate threonine-containing H(+)-ATPase (non-pT H(+)-ATPase) as in the green algae and that pT H(+)-ATPase is regulated by phosphorylation of its penultimate threonine. A search in the expressed sequence tag database of M. polymorpha revealed eight H(+)-ATPase genes, designated MpHA (for M. polymorpha H(+)-ATPase). Four isoforms are the pT H(+)-ATPase; the remaining isoforms are non-pT H(+)-ATPase. An apparent 95-kD protein was recognized by anti-H(+)-ATPase antibodies against an Arabidopsis (Arabidopsis thaliana) isoform and was phosphorylated on the penultimate threonine in response to the fungal toxin fusicoccin in thalli, indicating that the 95-kD protein contains pT H(+)-ATPase. Furthermore, we found that the pT H(+)-ATPase in thalli is phosphorylated in response to light, sucrose, and osmotic shock and that light-induced phosphorylation depends on photosynthesis. Our results define physiological signals for the regulation of pT H(+)-ATPase in the liverwort M. polymorpha, which is one of the earliest plants to acquire pT H(+)-ATPase.
质膜 H(+)-ATP 酶在质膜两侧产生 H(+)电化学梯度，为溶质转运提供驱动力，并调节植物细胞的 pH 平衡和膜电位。最近的研究表明，H(+)-ATP 酶倒数第 2 位苏氨酸的磷酸化以及随后与 14-3-3 蛋白的结合是维管植物中 H(+)-ATP 酶的主要共同激活机制。然而，关于非维管束植物苔藓植物的质膜 H(+)-ATP 酶的信息却很少。在这里，我们表明，作为现存陆地植物最基础的谱系的地钱（Marchantia polymorpha）既表达了含有倒数第 2 位苏氨酸的 H(+)-ATP 酶（pT H(+)-ATP 酶），也表达了不含倒数第 2 位苏氨酸的 H(+)-ATP 酶（非 pT H(+)-ATP 酶），就像绿藻一样，并且 pT H(+)-ATP 酶的活性受到其倒数第 2 位苏氨酸磷酸化的调节。在地钱的表达序列标签数据库中进行搜索，发现了 8 个 H(+)-ATP 酶基因，命名为 MpHA（用于 M. polymorpha H(+)-ATP 酶）。其中 4 个同工型是 pT H(+)-ATP 酶；其余同工型是非 pT H(+)-ATP 酶。抗拟南芥（Arabidopsis thaliana）同工型的 H(+)-ATP 酶抗体识别到一个表观分子量为 95kDa 的蛋白，并在真菌毒素 fusicoccin 作用下在叶状体中磷酸化倒数第 2 位苏氨酸，表明 95kDa 的蛋白含有 pT H(+)-ATP 酶。此外，我们发现叶状体中的 pT H(+)-ATP 酶在响应光、蔗糖和渗透冲击时发生磷酸化，而光诱导的磷酸化依赖于光合作用。我们的研究结果确定了调控地钱 pT H(+)-ATP 酶的生理信号，地钱是最早获得 pT H(+)-ATP 酶的植物之一。
