Function and regulation of macroautophagy in plants.

The plant vacuole is a major site for the degradation of macromolecules, which are transferred from the cytoplasm by autophagy via double-membrane vesicles termed autophagosomes. Autophagy functions at a basal level under normal growth conditions and is induced during senescence and upon exposure to stress conditions to recycle nutrients or degrade damaged proteins and organelles. Autophagy is also required for the regulation of programmed cell death as a response to pathogen infection and possibly during certain developmental processes. Little is known about how autophagy is regulated under these different conditions in plants, but recent evidence suggests that plants contain a functional TOR pathway which may control autophagy induction in conjunction with hormonal and/or environmental signals.