The VaATG6-VaBI-1 module coordinates ER-associated autophagy and ROS homeostasis for cold tolerance in grapevine

Cold stress is a major constraint on plant productivity, especially in perennial crops like grapevine (Vitis spp.), where it disrupts cellular homeostasis and induces oxidative damage. Here, we identify VaATG6, a key regulator of autophagy, and its interaction with VaBI-1, an ER-localized modulator, as central components of the cold stress response in Vitis amurensis. Cold exposure rapidly induced VaATG6 transcription and triggered its dynamic relocalization from the nucleus to the ER and autophagosomes, enhancing autophagic flux, reducing reactive oxygen species (ROS) accumulation, and improving cold tolerance. In contrast, VaBI-1 acted as a modulator, fine-tuned autophagy and ROS levels through its interaction with VaATG6. Notably, cold stress strengthened the VaATG6-VaBI-1 interaction, linking a coordinated mechanism that integrated autophagy with ER homeostasis. Overexpression of VaATG6 in cold-sensitive V. vinifera enhanced antioxidant defenses and promoted soluble sugar accumulation, significantly improving cold tolerance. Conversely, VaATG6 loss-of-function mutants exhibited impaired autophagy, elevated ROS accumulation, and increased cold sensitivity. These findings establish the VaATG6-VaBI-1 regulatory module as a core mechanism for cold-induced autophagy and oxidative stress adaptation. Our results highlight VaATG6 overexpression and VaBI-1 modulation as promising genetic strategies to enhance cold tolerance in perennial crops.