Use it or average it: stochasticity in plant development

•Stochastic fluctuations can initiate developmental patterning.•Robustness mechanisms can be identified via mutants that increase variability.•Variability can produce regularity through spatiotemporal averaging.

A process that is stochastic has a probabilistic or randomly determined outcome. At the molecular level, all processes are stochastic; but development is highly reproducible, suggesting that plants and other multicellular organisms have evolved mechanisms to ensure robustness (achieving correct development despite stochastic and environmental perturbations). Mechanisms of robustness can be discovered through isolating mutants with increased variability in phenotype; such mutations do not necessarily change the average phenotype. Surprisingly, some developmental robustness mechanisms actually exploit stochasticity as a useful source of variation. For example, gene expression is stochastic and can be utilized to create subtle differences between identical cells that can initiate the patterning of specialized cell types. Stochasticity can also be used to promote robustness through spatiotemporal averaging - stochasticity can be averaged out across space and over time. Thus, organisms often harness stochasticity to ensure robust development.