Tulin Frej, Cross Frederick R
The Rockefeller University, New York, New York 10065.
The Rockefeller University, New York, New York 10065
Plant Cell. 2014 Oct;26(10):4019-38. doi: 10.1105/tpc.114.129312. Epub 2014 Oct 21.
Research in yeast and animals has resulted in a well-supported consensus model for eukaryotic cell cycle control. The fit of this model to early diverging eukaryotes, such as the plant kingdom, remains unclear. Using the green alga Chlamydomonas reinhardtii, we developed an efficient pipeline, incorporating robotics, semiautomated image analysis, and deep sequencing, to molecularly identify >50 genes, mostly conserved in higher plants, specifically required for cell division but not cell growth. Mutated genes include the cyclin-dependent kinases CDKA (resembling yeast and animal Cdk1) and the plant-specific CDKB. The Chlamydomonas cell cycle consists of a long G1 during which cells can grow >10-fold, followed by multiple rapid cycles of DNA replication and segregation. CDKA and CDKB execute nonoverlapping functions: CDKA promotes transition between G1 and entry into the division cycle, while CDKB is essential specifically for spindle formation and nuclear division, but not for DNA replication, once CDKA-dependent initiation has occurred. The anaphase-promoting complex is required for similar steps in the Chlamydomonas cell cycle as in Opisthokonts; however, the spindle assembly checkpoint, which targets the APC in Opisthokonts, appears severely attenuated in Chlamydomonas, based on analysis of mutants affecting microtubule function. This approach allows unbiased integration of the consensus cell cycle control model with innovations specific to the plant lineage.
对酵母和动物的研究已经得出了一个得到充分支持的真核细胞周期控制共识模型。该模型与早期分化的真核生物（如植物界）的契合度仍不明确。我们利用莱茵衣藻这种绿藻，开发了一种高效流程，整合了机器人技术、半自动图像分析和深度测序，以便从分子层面鉴定出50多个基因，其中大多数在高等植物中保守存在，这些基因是细胞分裂而非细胞生长所特需的。突变基因包括细胞周期蛋白依赖性激酶CDKA（类似于酵母和动物的Cdk1）以及植物特有的CDKB。衣藻的细胞周期包括一个较长的G1期，在此期间细胞可以生长超过10倍，随后是多个快速的DNA复制和分离周期。CDKA和CDKB执行不重叠的功能：CDKA促进G1期向分裂周期的转变，而CDKB一旦发生依赖CDKA的起始后，对纺锤体形成和核分裂至关重要，但对DNA复制并非必需。后期促进复合体在衣藻细胞周期中所需的步骤与在后鞭毛生物中类似；然而，基于对影响微管功能的突变体的分析，在后鞭毛生物中靶向后期促进复合体的纺锤体组装检查点在衣藻中似乎严重减弱。这种方法能够将细胞周期控制共识模型与植物谱系特有的创新进行无偏整合。
