Weill Institute for Cell and Molecular Biology and Section of Plant Biology, School of Integrative Plant Sciences, Cornell University, Ithaca, NY 14853, USA.
Laboratoire de Reproduction et Développement des Plantes, Université de Lyon, ENS de Lyon, UCBL, INRA, CNRS, 46 Allée d'Italie, 69364 Lyon Cedex 07, France; Laboratoire Joliot Curie, CNRS, ENS de Lyon, Université de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
Dev Cell. 2016 Jul 11;38(1):15-32. doi: 10.1016/j.devcel.2016.06.016.
Organ sizes and shapes are strikingly reproducible, despite the variable growth and division of individual cells within them. To reveal which mechanisms enable this precision, we designed a screen for disrupted sepal size and shape uniformity in Arabidopsis and identified mutations in the mitochondrial i-AAA protease FtsH4. Counterintuitively, through live imaging we observed that variability of neighboring cell growth was reduced in ftsh4 sepals. We found that regular organ shape results from spatiotemporal averaging of the cellular variability in wild-type sepals, which is disrupted in the less-variable cells of ftsh4 mutants. We also found that abnormal, increased accumulation of reactive oxygen species (ROS) in ftsh4 mutants disrupts organ size consistency. In wild-type sepals, ROS accumulate in maturing cells and limit organ growth, suggesting that ROS are endogenous signals promoting termination of growth. Our results demonstrate that spatiotemporal averaging of cellular variability is required for precision in organ size.
器官的大小和形状具有惊人的可重复性，尽管其中的单个细胞会发生不同的生长和分裂。为了揭示是什么机制使这种精确性成为可能，我们设计了一个针对拟南芥萼片大小和形状均匀性中断的筛选实验，并鉴定出了线粒体 i-AAA 蛋白酶 FtsH4 的突变。出乎意料的是，通过实时成像，我们观察到 ftsh4 萼片中相邻细胞生长的可变性降低。我们发现，规则的器官形状是由野生型萼片中细胞可变性的时空平均产生的，而在 ftsh4 突变体中这种可变性会被打乱。我们还发现，异常的、增加的活性氧（ROS）积累会破坏 ftsh4 突变体的器官大小一致性。在野生型萼片中，ROS 积累在成熟细胞中并限制器官生长，这表明 ROS 是促进生长终止的内源性信号。我们的结果表明，细胞可变性的时空平均是器官大小精确性所必需的。
