Gibberellin (GA) is a phytohormone that regulates key developmental processes in plants, including seed germination and photomorphogenesis. It is well established that GA signaling involves GA-triggered, 26S proteasome-dependent degradation of DELLA proteins. Whether DELLA proteins also undergo autophagic degradation to mediate GA signaling remains unclear. In this study, we investigated the responsiveness of Arabidopsis seedlings to GA and the dynamics of DELLA proteins under nutrient starvation in darkness. We found that GA-induced seed germination and skotomorphogenesis are impaired in autophagy mutants and that GA promotes the autophagic degradation of DELLA proteins. Biochemical and protein localization an... More
Gibberellin (GA) is a phytohormone that regulates key developmental processes in plants, including seed germination and photomorphogenesis. It is well established that GA signaling involves GA-triggered, 26S proteasome-dependent degradation of DELLA proteins. Whether DELLA proteins also undergo autophagic degradation to mediate GA signaling remains unclear. In this study, we investigated the responsiveness of Arabidopsis seedlings to GA and the dynamics of DELLA proteins under nutrient starvation in darkness. We found that GA-induced seed germination and skotomorphogenesis are impaired in autophagy mutants and that GA promotes the autophagic degradation of DELLA proteins. Biochemical and protein localization analyses revealed that GA promotes the nuclear export of DELLA proteins and ATG8, their co-localization in autophagosomes, and autophagosome formation. Further biochemical studies demonstrated that GA enhances the interaction between ATG8 and GID1, thereby promoting the association of ATG8 with DELLA proteins and their autophagic degradation. Through this mechanism, GA promotes seed germination and skotomorphogenesis under nutrient starvation in darkness, enabling seedlings to penetrate the soil rapidly, capture sunlight, and shift to autotrophic growth to overcome nutrient deficiency.
