March 2, 2018

Groups of cells switch between uniform and variable growth during plant development

Dynamic changes in the variability of cell growth are crucial for the consistent development of plant organs

small image of clones overlaid on a microscopy image of a sepal

Figure 1: Clones (marked in color, with white lines indicating cell division within a clone) overlaid on a microscopy image of a sepal.

Adapted from Ref. 1 and licensed under CC BY 4.0 © 2018 Tsugawa et al.

A complex interplay between growth rate and variability underpins the development of some plant organs, according to a new study by RIKEN scientists1. The findings highlight the importance of a multiscale perspective for understanding plant development.

The research builds on an earlier study2 that showed that variability in cell growth is essential for the proper growth of sepals, the outermost parts of flowers. Mutant plants with reduced variability failed to reliably form sepals of the right size and shape—in other words, reduced variability at the cellular level led to greater variability at the organ level.

“In conventional biological stories, researchers focus on the cellular level or the organ level. There are very few efforts to analyze growth at different scales,” says Satoru Tsugawa of the Theoretical Biology Laboratory at RIKEN, who was involved in both studies. “A multiscale analysis might give a better understanding of growth.”

As a first step toward understanding how variability links different levels of development, the researchers took microscopy images of Arabidopsis sepals every 12 hours and then used software to identify the individual cells and track them over time. This enabled them to follow the growth of an individual cell and all of its descendants (‘clones’) during sepal development (Fig. 1).

Their analysis revealed two distinct stages of cellular growth. In the early phases of sepal development, cell growth reduces the size differences between clones, a process the team called uniformization. In other words, smaller clones grew more quickly than larger clones.

But after several days, growth switched to a different pattern in which the clones grew in proportion to their size, enhancing the difference between small and large clones. The factors that control the transition from uniformization to variability enhancement remain unknown, but the researchers ruled out a link to changes in cell position or identity.

The team also found a correlation between the variability within a clone and its growth rate. There was more variation in the growth rate of cells within faster growing clones, although the causes and consequences of this phenomenon remain unclear.

Tsugawa reports that researchers studying roots and leaves want to determine whether similar processes are at play in the development of those organs. Meanwhile, his team plans to continue investigating sepal growth variation. “We plan to systematically study growth at different scales, from the subcellular scale to the organs,” he says. “We will analyze the different scales and try to find the relationship connecting cellular variability and organ consistency. That’s our goal.”


  1. Tsugawa, S., Hervieux, N., Kierzkowski, D., Routier-Kierzkowska, A.-L., Sapala, A., Hamant, O., Smith, R. S., Roeder, A. H. K, Boudaoud, A. & Li, C.-B. Clones of cells switch from reduction to enhancement of size variability in Arabidopsis sepals. Development 144, 4398–4405 (2017). doi: 10.1242/dev.153999
  2. Hong, L., Dumond, M., Tsugawa, S., Sapala, A., Routier-Kierzkowska, A.-L., Zhou, Y., Chen, C., Kiss, A., Zhu, M., Hamant, O. et al. Variable cell growth yields reproducible organ development through spatiotemporal averaging. Developmental Cell 38, 15–32 (2016). doi: 10.1016/j.devcel.2016.06.016