Die for living better: plants modify root system architecture through inducing PCD in root meristem under severe water stress.

Plant root development is highly plastic in order to cope with various environmental stresses; many questions on the mechanisms underlying developmental plasticity of root system remain unanswered. Recently, we showed that autophagic PCD occurs in the region of root apical meristem in response to severe water deficit. We provided evidence that reactive oxygen species (ROS) accumulation may trigger the cell death process of the meristematic cells in the stressed root tips. Analysis of BAX inhibitor-1 (AtBI1) expression and the phenotypic response of atbi1-1 mutant under the severe water stress revealed that AtBI1 and the endoplasmic reticulum (ER) stress response pathway modulate water stress-induced PCD. As a result, the thick and short lateral roots with increased tolerance to the stress are induced. We propose that under severe drought condition, plants activate PCD program in the root apical root meristem, so that apical root dominance is removed. In this way, they can remodel their root system architecture to adapt the stress environment.