The Interplay between Plant Autophagy and Carbon Availability

Plants produce their energy source by fixing carbon from the air through photosynthesis. However, under some conditions in which photosynthesis is downregulated, carbon supply is limited. Therefore, the plant must use other resources to meet its energy demands. Nutrient supply is met, at least partially, by the degradation of cellular components, resulting in pronounced metabolic changes. The regulation of carbon availability and remobilization in the plant is thus tightly regulated.

Autophagy is a conserved eukaryotic process for the degradation of cellular constituents in the lytic compartment (vacuole in yeast and plants and lysosome in animals). The targets of autophagy are diverse and include soluble proteins, protein aggregates, whole organelles, and lipids. The autophagy mechanism is highly conserved, and homologs of many autophagy-related (ATG) genes have been characterized in plants. The hallmark phenotype of autophagy-related mutants (atg mutants) is higher sensitivity nutrient starvation, early senescence, and lower yield. However, the direct impact of autophagy on cellular metabolism has not been well studied.

Our group studies nutrient remobilization in plants, focusing on autophagy as a model system for this process. We investigated the role of autophagy in various carbon regimens, by comparing WT and atg mutant Arabidopsis thaliana plants. We could observe morphological differences between the mutants and WT plants, suggesting hypersensitivity to carbon starvation and reduced sensitivity to sugar excess. We also employed autophagy activity assay and metabolic profiling to understand the mechanism behind the morphological phenotype and uncover the regulation of carbon quantities in the plant by the autophagy mechanism.