Raffinose induces autophagy to promote plant growth

Abstract

Plant growth is governed by the integration of environmental cues and nutritional status. Under stress conditions, growth is usually attenuated in favor of stress response, creating a trade-off between growth and stress. Autophagy is a vital process in eukaryotes, maintaining cellular balance by degrading and recycling cellular components. It is triggered by various nutrient-deprivation conditions and both biotic and abiotic stresses in plants. Surprisingly, over-expressing autophagy-related genes across multiple plant species resulted in increased plant size, yield, and stress resistance, posing autophagy as a regulator of the stress-growth balance. Yet, the molecular mechanisms governing its induction remain partially understood. In the current work, we identified raffinose-a plant-derived sugar known for its role in stress responses-as a novel plant autophagy inducer. Raffinose treatment resulted in increased biomass and yield in an autophagy-dependent manner in several plant species. We also show that raffinose activates autophagy through the SnRK1 kinase complex, independent of TOR signaling, and that raffinose treatment results in increased expression of ATG5 and ATG7. We also point to possible downstream candidates operating autophagy-related biomass accumulation. Our findings offer new perspectives on the role of autophagy in maintaining a balance between plant growth and stress responses, underscoring the significance of raffinose in its regulation. SIGNIFICANCE STATEMENTThe intricate balance between plant growth and stress responses is crucial for agricultural productivity, particularly as climate change intensifies environmental stressors such as drought and extreme temperatures. Usually, there is a trade-off between growth and stress response. Autophagy--a cellular recycling process essential for maintaining cellular homeostasis--plays a pivotal role in this balance. Yet, the molecular mechanisms modulating it are partially understood. Raffinose treatment enhances biomass and yields in various plant species by inducing autophagy. By elucidating the molecular mechanisms of raffinose-mediated autophagy induction, our findings provide valuable insights into potential strategies for enhancing plant resilience against climate-induced stress.