Illuminating the regulatory link between blue light and autophagy in photomorphogenesis

Cryptochrome 1 (CRY1) promotes photomorphogenesis primarily by inhibiting Constituttive photomorphogenic 1 (COP1)/Suppressor of PHYA-105 1 (SPA1)-mediated degradation of HY5 via the 26S proteasome degradation pathway. However, it remained unknown whether autophagy, a conserved vacuolar recycling process induced by nutrient starvation, also participates in blue light signaling. Our latest study reveals that in Arabidopsis thaliana, under nutrient starvation, Autophagy-related 8 (ATG8) binds and targets Elongated hypocotyl 5 (HY5) for vacuolar degradation in darkness, thereby promoting skotomorphogenesis. Upon blue-light activation, however, CRY1 binds to ATG8 and blocks its interaction with HY5, which in turn inhibits the autophagic degradation of HY5 and promotes photomorphogenesis. Our findings thus establish a direct photoreceptor – autophagy functional connection that integrates light and nutrient cues to govern developmental transitions in plants.