Jonsson Erik, Yamada Moé, Vale Ronald D, Goshima Gohta
Marine Biological Laboratory (MBL), Woods Hole, Massachusetts 02543, USA ; Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, UCSF, 600 16th St., San Francisco, California 94158, USA.
Marine Biological Laboratory (MBL), Woods Hole, Massachusetts 02543, USA ; Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
Nat Plants. 2015 Jul;1(7). doi: 10.1038/NPLANTS.2015.87.
The molecular motors kinesin and dynein drive bidirectional motility along microtubules (MTs) in most eukaryotic cells. Land plants, however, are a notable exception, because they contain a large number of kinesins but lack cytoplasmic dynein, the foremost processive retrograde transporter. It remains unclear how plants achieve retrograde cargo transport without dynein. Here, we have analysed the motility of the six members of minus-end-directed kinesin-14 motors in the moss and found that none are processive as native dimers. However, when artificially clustered into as little as dimer of dimers, the type-VI kinesin-14 (a homologue of KCBP (kinesin-like calmodulin binding protein)) exhibited highly processive and fast motility (up to 0.6 μm s). Multiple kin14-VI dimers attached to liposomes also induced transport of this membrane cargo over several microns. Consistent with these results, observations of green fluorescent protein-tagged kin14-VI in moss cells revealed fluorescent punctae that moved processively towards the minus-ends of the cytoplasmic MTs. These data suggest that clustering of a kinesin-14 motor serves as a dynein-independent mechanism for retrograde transport in plants.
在大多数真核细胞中，分子马达驱动蛋白和动力蛋白沿着微管（MTs）进行双向运动。然而，陆地植物是一个显著的例外，因为它们含有大量的驱动蛋白，但缺乏胞质动力蛋白，即最重要的持续逆行转运体。目前尚不清楚植物在没有动力蛋白的情况下如何实现货物的逆行运输。在这里，我们分析了苔藓中六种负端定向驱动蛋白-14马达成员的运动性，发现没有一种作为天然二聚体具有持续性。然而，当人工聚集成低至二聚体的二聚体时，VI型驱动蛋白-14（KCBP（类驱动蛋白钙调蛋白结合蛋白）的同源物）表现出高度持续和快速的运动性（高达0.6μm/s）。附着在脂质体上的多个kin14-VI二聚体也能诱导这种膜货物在几微米的距离上运输。与这些结果一致，在苔藓细胞中对绿色荧光蛋白标记的kin14-VI的观察显示，荧光斑点向胞质微管的负端持续移动。这些数据表明，驱动蛋白-14马达的聚集是植物中一种不依赖动力蛋白的逆行运输机制。
