Department of Biology, Stanford University, Stanford, CA 94305, USA.
Howard Hughes Medical Institute (HHMI), Stanford University, Stanford, CA 94305, USA.
Development. 2018 Mar 21;145(6):dev160671. doi: 10.1242/dev.160671.
Plants, with cells fixed in place by rigid walls, often utilize spatial and temporally distinct cell division programs to organize and maintain organs. This leads to the question of how developmental regulators interact with the cell cycle machinery to link cell division events with particular developmental trajectories. In leaves, the development of stomata, two-celled epidermal valves that mediate plant-atmosphere gas exchange, relies on a series of oriented stem cell-like asymmetric divisions followed by a single symmetric division. The stomatal lineage is embedded in a tissue in which other cells transition from proliferation to postmitotic differentiation earlier, necessitating stomatal lineage-specific factors to prolong competence to divide. We show that the D-type cyclin, CYCD7;1, is specifically expressed just prior to the symmetric guard cell-forming division, and that it is limiting for this division. Further, we find that CYCD7;1 is capable of promoting divisions in multiple contexts, likely through RBR1-dependent promotion of the G1/S transition, but that CYCD7;1 is regulated at the transcriptional level by cell type-specific transcription factors that confine its expression to the appropriate developmental window.
植物的细胞被刚性细胞壁固定在原位，通常利用空间和时间上不同的细胞分裂程序来组织和维持器官。这就提出了一个问题，即发育调节剂如何与细胞周期机制相互作用，将细胞分裂事件与特定的发育轨迹联系起来。在叶片中，气孔的发育，即介导植物-大气气体交换的两个细胞表皮瓣，依赖于一系列定向的干细胞样不对称分裂，随后是一个单一的对称分裂。气孔谱系嵌入在一种组织中，其中其他细胞更早地从增殖过渡到有丝分裂后分化，需要气孔谱系特异性因子来延长分裂能力。我们表明，D 型细胞周期蛋白 CYCD7;1 仅在对称的保卫细胞形成分裂之前特异性表达，并且它对该分裂是有限的。此外，我们发现 CYCD7;1 能够在多种情况下促进分裂，可能是通过 RBR1 依赖性促进 G1/S 过渡，但 CYCD7;1 的转录水平受到细胞类型特异性转录因子的调节，这些转录因子将其表达限制在适当的发育窗口内。
