Waizenegger I, Lukowitz W, Assaad F, Schwarz H, Jürgens G, Mayer U
ZMBP, Entwicklungsgenetik, Universität Tübingen, Auf der Morgenstelle 1, Tübingen, Germany.
Curr Biol. 2000 Nov 2;10(21):1371-4. doi: 10.1016/s0960-9822(00)00775-2.
Partitioning of the cytoplasm during cytokinesis or cellularisation requires syntaxin-mediated membrane fusion [1-3]. Whereas in animals, membrane fusion promotes ingression of a cleavage furrow from the plasma membrane [4,5], somatic cells of higher plants form de novo a transient membrane compartment, the cell plate, which is initiated in the centre of the division plane and matures into a new cell wall and its flanking plasma membranes [6,7]. Cell plate formation results from the fusion of Golgi-derived vesicles delivered by a dynamic cytoskeletal array, the phragmoplast. Mutations in two Arabidopsis genes, KNOLLE (KN) and KEULE (KEU), cause abnormal seedlings with multinucleate cells and incomplete cell walls [1,8]. The KN gene encodes a cytokinesis-specific syntaxin which localises to the cell plate [9]. Here, we show that KN protein localisation is unaffected in keu mutant cells, which, like kn, display phragmoplast microtubules and accumulate ADL1 protein in the plane of cell division but vesicles fail to fuse with one another. Genetic interactions between KN and KEU were analysed in double mutant embryos. Whereas the haploid gametophytes gave rise to functional gametes, the embryos behaved like single cells displaying multiple, synchronously cycling nuclei, cell cycle-dependent microtubule arrays and ADL1 accumulation between pairs of daughter nuclei. This complete inhibition of cytokinesis from fertilisation indicates that KN and KEU, have partially redundant functions and interact specifically in vesicle fusion during cytokinesis of somatic cells.
在胞质分裂或细胞化过程中，细胞质的分隔需要Syntaxin介导的膜融合[1 - 3]。在动物中，膜融合促进了来自质膜的分裂沟的内陷[4,5]，而高等植物的体细胞则重新形成一个短暂的膜区室——细胞板，它在分裂平面的中心起始，并发育成新的细胞壁及其两侧的质膜[6,7]。细胞板的形成是由动态细胞骨架阵列——成膜体传递的高尔基体衍生囊泡融合的结果。拟南芥的两个基因KNOLLE（KN）和KEULE（KEU）发生突变会导致幼苗异常，出现多核细胞和不完整的细胞壁[1,8]。KN基因编码一种定位于细胞板的胞质分裂特异性Syntaxin[9]。在这里，我们表明KN蛋白的定位在keu突变体细胞中不受影响，keu突变体细胞与kn突变体细胞一样，有成膜体微管，并在细胞分裂平面积累ADL1蛋白，但囊泡无法相互融合。在双突变胚胎中分析了KN和KEU之间的遗传相互作用。单倍体配子体产生了功能性配子，而胚胎的行为则像单细胞，显示出多个同步循环的细胞核、细胞周期依赖性微管阵列以及在子核对之间积累ADL1。从受精开始对胞质分裂的完全抑制表明，KN和KEU具有部分冗余功能，并且在体细胞胞质分裂期间的囊泡融合中特异性相互作用。
