The role of ER stress-depending autophagy under phosphate deprivation (Plant Physiol)

In the Brassicaceae, inorganic phosphate (Pi) deprivation modifies root system architecture to favor Pi foraging, through the inhibition of primary root growth and the stimulation of lateral root growth. Root growth inhibition is triggered by Fe-stimulated ROS generation and cell wall modifications, which cause ER stress and could induce autophagy. Autophagy is a process that has been studied under other nutrient starvation stressors (carbon, nitrogen and sulfur) but not Pi deprivation. Naumann and colleagues studied the effect of Pi deprivation in autophagy using a variety of Arabidopsis mutants. They found that ER stress-dependent autophagy is quickly activated in response to Pi limitation in roots, and this activation requires the genetic PDR2 (ER-resident P5-type ATPase)-LPR1 (cell-wall-target ferroxidase) module. Thus, the root-localized Pi-dependent activation of autophagy is due to local Pi sensing and related ER stress responses. (Summary by Julia Miller) Plant Physiol. 10.1104/pp.18.01379