CANE1-mediated autophagosome size regulation fine-tunes phosphate starvation tolerance in Arabidopsis thaliana

Abstract

Inorganic phosphate (Pi) availability determines root development and plant performance. In Arabidopsis thaliana, external Pi is sensed by root tips and Pi limitation triggers ER stress-induced autophagy, yet the physiological impact and mechanisms controlling autophagosome biogenesis remain unclear. Here, we identify CANE1 (COMPONENT OF AUTOPHAGIC NETWORK) as a novel plant-specific regulator of autophagosome size in local Pi sensing. CANE1 associates with the plasma membrane-ER tethering protein VAP27-1 and binds to Pi-responsive ATG8 isoforms through conserved interaction motifs. Loss of CANE1 augments ER stress resistance by reducing autophagosome size in Pi-deprived root tips. Our findings establish CANE1 as a determinant of autophagosome size at the ER membrane. Thus, CANE1 functions as a molecular link between Pi-dependent ER stress signaling and fine-tuning of autophagic capacity.