Photoexcited CRY1 physically interacts with ATG8 to regulate selective autophagy of HY5 and photomorphogenesis in <i>Arabidopsis</i>

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.