Autophagic recycling: lessons from yeast help define the process in plants.

The autophagic engulfment of cytoplasm and organelles and their delivery to the vacuole have long been speculated to play an essential role in bulk protein turnover in plants. Until recently, however, the importance and the mechanism(s) of action of these processes have remained obscure. Aided by the discovery of numerous orthologs of the yeast AUTOPHAGY (ATG) protein system in Arabidopsis, significant advances have been now made in understanding these processes. Both reverse genetic analyses of the Arabidopsis ATG genes and the use of the encoded proteins as cytological markers have confirmed the presence of autophagy in plants and have demonstrated its importance in nutrient recycling, especially during senescence and growth under carbon- or nitrogen-limiting conditions.