Photoexcited CRY1 physically interacts with ATG8 to regulate selective autophagy of HY5 and photomorphogenesis in Arabidopsis.

Cryptochromes (CRYs) are blue light photoreceptors that regulate various light responses in plants, including photomorphogenesis. Autophagy is a tightly controlled intracellular degradation pathway that plays a critical role in plant growth and development. CRY signaling inhibits the 26S proteasome-dependent degradation of LONG HYPOCOTYL 5 (HY5) through interactions with the CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1)-SUPPRESSOR OF PHYA-105 1 (SPA1) complex. However, whether CRY1 mediates the blue light-driven regulation of photomorphogenesis by regulating the autophagic degradation of HY5 remains unclear. Here, we show that CRY1 directly interacts with ATG8, a key player in selective autophagy, in a blue light-dependent manner in Arabidopsis (Arabidopsis thaliana). ATG8 and ATG5/ATG7 act genetically downstream of CRY1, but upstream of HY5, to regulate photomorphogenesis. In darkness, AUTOPHAGY-RELATED8 (ATG8) physically interacts with HY5 to facilitate its autophagic degradation and promote skotomorphogenesis. Under blue light, the CRY1-ATG8 interaction inhibits the ATG8-HY5 interaction, suppressing the nuclear export and co-localization of ATG8 and HY5 to the autophagosome, and HY5 degradation in the vacuole. This study reveals how CRY1-mediated blue light signaling regulates HY5 autophagy, which enables plants to fine-tune photomorphogenic development in response to light and nutrient availability.