Fig. 8: A proposed model showing the regulatory function of MdATG8i in response to long-term moderate drought stress in apple.

Under long-term moderate drought conditions, MdATG8i overexpression contributes to maintaining optimal stomatal aperture and organized chloroplasts, resulting in greater photosynthetic capacity and thus higher WUE. Moreover, increased expression of MdATG8i also modulates the accumulation of sugar and amino acids in response to long-term drought stress, resulting in better osmotic adjustment as well as higher WUE and drought adaptability. Most importantly, MdATG8i overexpression promotes autophagic activity, which was likely related to the above changes, eventually resulting in improved WUE and drought adaptability.