Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, Aichi 464-8601, Japan; Institute for Advanced Research (IAR), Nagoya University, Nagoya, Aichi 464-8601, Japan.
Howard Hughes Medical Institute, The University of Texas at Austin, Austin, TX 78712, USA; Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA.
Dev Cell. 2022 Mar 14;57(5):569-582.e6. doi: 10.1016/j.devcel.2022.01.014. Epub 2022 Feb 10.
Differentiation of specialized cell types requires precise cell-cycle control. Plant stomata are generated through asymmetric divisions of a stem-cell-like precursor followed by a single symmetric division that creates paired guard cells surrounding a pore. The stomatal-lineage-specific transcription factor MUTE terminates the asymmetric divisions and commits to differentiation. However, the role of cell-cycle machineries in this transition remains unknown. We discover that the symmetric division is slower than the asymmetric division in Arabidopsis. We identify a plant-specific cyclin-dependent kinase inhibitor, SIAMESE-RELATED4 (SMR4), as a MUTE-induced molecular brake that decelerates the cell cycle. SMR4 physically and functionally associates with CYCD3;1 and extends the G1 phase of asymmetric divisions. By contrast, SMR4 fails to interact with CYCD5;1, a MUTE-induced G1 cyclin, and permits the symmetric division. Our work unravels a molecular framework of the proliferation-to-differentiation switch within the stomatal lineage and suggests that a timely proliferative cell cycle is critical for stomatal-lineage identity.
特化细胞类型的分化需要精确的细胞周期控制。植物气孔通过类似于干细胞的前体细胞的不对称分裂产生，然后进行一次对称分裂，形成一对围绕着孔的保卫细胞。气孔谱系特异性转录因子 MUTE 终止不对称分裂并促使细胞分化。然而，细胞周期机制在这个转变中的作用仍然未知。我们发现拟南芥中的对称分裂比不对称分裂慢。我们鉴定出一个植物特异性的细胞周期蛋白依赖性激酶抑制剂，SMR4，作为 MUTE 诱导的分子刹车，减缓细胞周期。SMR4 与 CYCD3;1 物理和功能相关，并延长不对称分裂的 G1 期。相比之下，SMR4 不能与 MUTE 诱导的 G1 周期蛋白 CYCD5;1 相互作用，并允许进行对称分裂。我们的工作揭示了气孔谱系内增殖到分化开关的分子框架，并表明适时的增殖细胞周期对于气孔谱系身份至关重要。
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