Department of Biology, Tokyo Gakugei University, 4-1-1 Nukuikita-machi, Koganei, Tokyo, 184-8501, Japan.
Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan.
Sci Rep. 2021 Jan 8;11(1):227. doi: 10.1038/s41598-020-80733-z.
Gravity is a critical environmental factor affecting the morphology and function of plants on Earth. Gravistimulation triggered by changes in the gravity vector induces an increase in the cytoplasmic free calcium ion concentration ([Ca]) as an early process of gravity sensing; however, its role and molecular mechanism are still unclear. When seedlings of Arabidopsis thaliana expressing apoaequorin were rotated from the upright position to the upside-down position, a biphasic [Ca]-increase composed of a fast-transient [Ca]-increase followed by a slow [Ca]-increase was observed. We find here a novel type [Ca]-increase, designated a very slow [Ca]-increase that is observed when the seedlings were rotated back to the upright position from the upside-down position. The very slow [Ca]-increase was strongly attenuated in knockout seedlings defective in MCA1, a mechanosensitive Ca-permeable channel (MSCC), and was partially restored in MCA1-complemented seedlings. The mechanosensitive ion channel blocker, gadolinium, blocked the very slow [Ca]-increase. This is the first report suggesting the possible involvement of MCA1 in an early event related to gravity sensing in Arabidopsis seedlings.
重力是影响地球上植物形态和功能的一个关键环境因素。由重力矢量变化引发的重力学刺激会引起细胞质游离钙离子浓度([Ca])增加，作为重力感应的早期过程；然而，其作用和分子机制尚不清楚。当拟南芥幼苗表达无辅基水母发光蛋白时，从垂直位置旋转到倒置位置，观察到由快速瞬时[Ca]增加随后是缓慢[Ca]增加组成的双相[Ca]增加。我们在这里发现了一种新型的[Ca]增加，称为非常缓慢的[Ca]增加，当幼苗从倒置位置旋转回垂直位置时观察到。在机械敏感性 Ca 渗透性通道 (MSCC) 缺陷型 MCA1 敲除幼苗中，非常缓慢的[Ca]增加强烈减弱，而在 MCA1 互补幼苗中部分恢复。机械敏感性离子通道阻滞剂钆阻断了非常缓慢的[Ca]增加。这是第一个表明 MCA1 可能参与拟南芥幼苗中与重力感应相关的早期事件的报告。
