How is robustness maintained during sepal development? Free

Organ development is a robust process, resulting in a reproducible organ size and shape across organisms. Altering the rates of cell division has been shown to not affect this robustness, as cells can compensate by changing their size and shape. However, the mechanisms that control this remain unclear. Here, Isabella Burda, Adrienne Roeder and colleagues investigate this robustness in the developing Arabidopsis thaliana sepal, the leaf-like organ that encloses the flower bud, by looking at a combination of mutants that affect cell division and cell growth rate heterogeneity. Using live imaging and cell growth tracking, the authors find that, in wild-type plants and plants with an increased or decreased number of cell divisions, the organ-scale growth pattern remains unaltered. However, mutants with altered cell growth variability display patches of faster and slower growth, and the robustness is lost. They conclude that this patchiness is due to correlations in growth rate over time and between neighbouring cells, and that in wild-type development, growth rates between cells are uncorrelated to allow regular sepal development to occur. Overall, the authors find that the amount of cell division does not affect the robustness of sepal development, but the variability of cellular growth rate must be uncorrelated or anti-correlated for robust development to occur.