Cleavage-furrow formation without F-actin in Chlamydomonas
Cleavage-furrow formation without F-actin in Chlamydomonas
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DOI：
10.1073/pnas.1920337117
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发表时间：
2020-08-04
影响因子：
11.1
通讯作者：
Pringle，John R.
中科院分区：
文献类型：
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作者：
Onishi，Masayuki;Umen，James G.;Pringle，John R.
人们普遍认为，在胞质分裂过程中，裂沟的形成是由含有F-肌动蛋白和II型肌球蛋白的环的收缩驱动的。然而，即使在具有这种环的细胞中，它们也不总是沟形成所必需的。此外，许多分类学上不同的真核细胞通过开沟进行分裂，但没有II型肌球蛋白，这使得肌动球蛋白环不太可能驱动开沟。为了进一步探讨这个问题，我们使用了一种这样的生物体，绿色藻类莱茵衣藻。我们发现，虽然F-肌动蛋白与沟区，没有三个肌球蛋白（类型VIII和XI）是本地化。此外，当通过突变和药物的组合消除F-肌动蛋白时，仍然形成犁沟，细胞分裂，尽管比正常情况下效率略低。出乎意料的是，在缺乏F-肌动蛋白的细胞中，大的Chlamydomonaschloroplast的分裂被延迟了;因为这个细胞器直接位于卵裂沟的路径上，这种延迟可以解释，至少部分地，胞质分裂本身的延迟。早期的研究表明，微管与卵裂沟的关联，我们使用荧光标记的EB 1蛋白显示，微管仍然与沟在F-肌动蛋白的情况下，一致的可能性，微管是重要的沟的形成。我们认为，肌动球蛋白环进化的一种方式，以提高效率的核心过程中已经存在于祖先真核生物的沟形成。
It is widely believed that cleavage-furrow formation during cytokinesis is driven by the contraction of a ring containing F-actin and type-II myosin. However, even in cells that have such rings, they are not always essential for furrow formation. Moreover, many taxonomically diverse eukaryotic cells divide by furrowing but have no type-II myosin, making it unlikely that an actomyosin ring drives furrowing. To explore this issue further, we have used one such organism, the green algaChlamydomonas reinhardtii. We found that although F-actin is associated with the furrow region, none of the three myosins (of types VIII and XI) is localized there. Moreover, when F-actin was eliminated through a combination of a mutation and a drug, furrows still formed and the cells divided, although somewhat less efficiently than normal. Unexpectedly, division of the largeChlamydomonaschloroplast was delayed in the cells lacking F-actin; as this organelle lies directly in the path of the cleavage furrow, this delay may explain, at least in part, the delay in cytokinesis itself. Earlier studies had shown an association of microtubules with the cleavage furrow, and we used a fluorescently tagged EB1 protein to show that microtubules are still associated with the furrows in the absence of F-actin, consistent with the possibility that the microtubules are important for furrow formation. We suggest that the actomyosin ring evolved as one way to improve the efficiency of a core process for furrow formation that was already present in ancestral eukaryotes.