Raffinose induces autophagy to promote the growth of Arabidopsis Thaliana

Background: Plant growth depends on the integration of environmental signals and nutrient availability. Under stress conditions, growth is often attenuated to prioritise defense, creating a trade-off between growth and stress responses. Autophagy, a conserved degradation and recycling mechanism in eukaryotes, plays a central role in maintaining cellular homeostasis during stress. Enhancing autophagy has been shown to improve growth, yield, and stress tolerance in plants, yet the molecular triggers that initiate this process are not fully understood. Results: We identified raffinose, a plant-derived sugar associated with stress responses, as a novel inducer of autophagy in plants. Exogenous application of raffinose stimulated autophagic activity and promoted biomass accumulation and seed yield in an autophagy-dependent manner across multiple plant species. Mechanistic analysis revealed that raffinose activates autophagy through SnRK1 in a TOR-independent manner, and that it upregulates the expression of autophagy-related genes ATG5 and ATG7. The growth-promoting effect of raffinose was specific and not replicated by equivalent carbon supplementation with glucose, while the raffinose precursor galactinol showed similar autophagy-dependent growth enhancement. Finally, we pointed to possible downstream candidates operating autophagy-related biomass accumulation, as identified by metabolic profiling. Conclusions: Our findings position raffinose as a signalling molecule capable of activating autophagy and enhancing plant growth and yield in a targeted, species-conserved manner. By linking a stress-associated sugar to the activation of a central catabolic pathway, this work reveals a potential mechanism by which plants may optimise the balance between growth and defense. Understanding raffinose-mediated autophagy induction can potentially provide new opportunities for developing strategies to improve crop performance under variable environmental conditions.