Building the differences: a case for the ground tissue patterning in plants.

A key question in biology is to understand how interspecies morphological diversities originate. Plant roots present a huge interspecific phenotypical variability, mostly because roots largely contribute to adaptation to different kinds of soils. One example is the interspecific cortex layer number variability, spanning from one to several. Here, we review the latest advances in the understanding of the mechanisms expanding and/or restricting cortical layer number in Arabidopsis thaliana and their involvement in cortex pattern variability among multi-cortical layered species such as Cardamine hirsuta or Oryza sativa.