State Key Laboratory of Protein and Plant Gene Research, School of Advanced Agricultural Sciences and School of Life Sciences, Peking University, Beijing, China.
Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China.
Nat Commun. 2021 Jul 22;12(1):4470. doi: 10.1038/s41467-021-24546-2.
Gravity is a critical environmental factor regulating directional growth and morphogenesis in plants, and gravitropism is the process by which plants perceive and respond to the gravity vector. The cytoskeleton is proposed to play important roles in gravitropism, but the underlying mechanisms are obscure. Here we use genetic screening in Physcomitrella patens, to identify a locus GTRC, that when mutated, reverses the direction of protonemal gravitropism. GTRC encodes a processive minus-end-directed KCHb kinesin, and its N-terminal, C-terminal and motor domains are all essential for transducing the gravity signal. Chimeric analysis between GTRC/KCHb and KCHa reveal a unique role for the N-terminus of GTRC in gravitropism. Further study shows that gravity-triggered normal asymmetric distribution of actin filaments in the tip of protonema is dependent on GTRC. Thus, our work identifies a microtubule-based cellular motor that determines the direction of plant gravitropism via mediating the asymmetric distribution of actin filaments.
重力是调节植物定向生长和形态发生的关键环境因素，向重力性是植物感知和响应重力矢量的过程。细胞骨架被认为在向重力性中发挥重要作用，但潜在的机制尚不清楚。在这里，我们使用 Physcomitrella patens 的遗传筛选，鉴定出一个突变后会逆转原丝体向重力性方向的基因 GTRC。GTRC 编码一个进行性的负端导向 KCHb 驱动蛋白，其 N 端、C 端和马达结构域对于转导重力信号都是必需的。GTRC/KCHb 和 KCHa 的嵌合分析揭示了 GTRC 的 N 端在向重力性中具有独特的作用。进一步的研究表明，重力触发的原丝体顶端肌动蛋白纤维的正常不对称分布依赖于 GTRC。因此，我们的工作鉴定了一种基于微管的细胞马达，它通过介导肌动蛋白纤维的不对称分布来决定植物向重力性的方向。
