Séminaire IBIP
Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)

Jeudi 24 septembre 2026 à 14h, Amphi 208

Nutrient Sensing – from Iron Homeostasis to ER Quality Control

External inorganic phosphate (Pi) availability profoundly affects plant performance. However, insolubility of most Pi salts and immobility of Pi complexed on clay minerals and metal (hydr)oxide surfaces severely restrict biologic Pi accessibility in many soils. To cope with this limitation, plants continuously monitor local Pi availability and adjust root development and cellular metabolism accordingly. But how root tips perceive external Pi availability and consequently adapt to dynamic nutrient access remains elusive.

In Arabidopsis thaliana, the specific bacterial-type ferroxidase LPR1 and the single ER-resident P5A-type ATPase PDR2 form a key regulatory module linking root growth to Pi availability through Fe-dependent signaling. LPR1 enzyme activity triggers profound changes in root meristem function in response to local root tip Pi sensing, while PDR2 maintains cellular homeostasis and restricts excessive stress responses. Our comparative genetic and biochemical studies of Arabidopsis mutants defective in local Pi sensing, ER stress response, and autophagy indicate that ER stress-dependent autophagy is rapidly activated as part of the developmental response of the root apex to Pi limitation and implicates PDR2/AtP5A as a central mediator of this process. Recent biochemical and genetic data on PDR2/AtP5A orthologues in S. cere­visiae and C. elegans uncovered ER-resident P5A-type ATPases to act as trans­mem­­brane helix dislocases, which facilitate the extraction of mistargeted tail-an­chored mem­brane proteins, to enforce ER protein quality control. To dissect the link between PDR2/AtP5A and the autophagic pathway and to understand the significance of Pi limitation-induced autophagy in plants, we used an untargeted approach to monitor global changes in the proteome of root tips. In addition to core autophagy proteins, which are known to be involved in and degraded by autophagy, our results indicate that local Pi sensing via LPR1 activity acts as a potent inducer of ER stress and ER stress-mediated autophagy, and therefore specifically influences proteostasis. The comparative proteomic data in combination with the recently obtained Pi-dependent PDR2-interactome point to PDR2 as a major hub for coordinating Pi sensing, ER quality control, and ER stress-activated autophagy in Arabidopsis root tips.

Contact : Stéphane Mari