This study demonstrates that yeast cells lacking vacuolar proteases undergo autophagy under nutrient-deficient conditions. When yeast cells deficient in proteinase A, B, and carboxypeptidase Y were transferred to a nutrient-poor medium, spherical bodies appeared in the vacuoles and gradually increased in number, filling the vacuoles completely after 3 hours. These bodies, called autophagic bodies, were surrounded by a thin unit membrane and contained cytoplasmic components such as ribosomes, RER, mitochondria, lipid granules, and glycogen granules. Electron microscopy confirmed that these bodies were sequestered in the vacuoles, suggesting autophagy. The accumulation of autophagic bodies was induced by nitrogen starvation, as well as by the depletion of carbon and amino acids, which halted the cell cycle. Genetic analysis showed that the accumulation of autophagic bodies was due to the absence of the PRB1 product, proteinase B. In the presence of PMSF, wild-type cells accumulated autophagic bodies in the vacuoles under nutrient-deficient conditions, similar to multiple protease-deficient mutants or cells with a disrupted PRB1 gene. The autophagic bodies disappeared rapidly after removal of PMSF, indicating they were an intermediate in the normal autophagic process. The study also showed that autophagic bodies contained cytosolic components, including ribosomes, and that their accumulation was not dependent on the presence of vacuolar proteases. The results suggest that autophagy in yeast is a general response to adverse conditions and that vacuolar proteases are essential for protein turnover under nutrient-deficient conditions. The study provides the first evidence that nutrient-deficient conditions induce extensive autophagic degradation of cytosolic components in yeast vacuoles. The findings support the idea that autophagy is a key mechanism for protein degradation and turnover in yeast under adverse conditions.This study demonstrates that yeast cells lacking vacuolar proteases undergo autophagy under nutrient-deficient conditions. When yeast cells deficient in proteinase A, B, and carboxypeptidase Y were transferred to a nutrient-poor medium, spherical bodies appeared in the vacuoles and gradually increased in number, filling the vacuoles completely after 3 hours. These bodies, called autophagic bodies, were surrounded by a thin unit membrane and contained cytoplasmic components such as ribosomes, RER, mitochondria, lipid granules, and glycogen granules. Electron microscopy confirmed that these bodies were sequestered in the vacuoles, suggesting autophagy. The accumulation of autophagic bodies was induced by nitrogen starvation, as well as by the depletion of carbon and amino acids, which halted the cell cycle. Genetic analysis showed that the accumulation of autophagic bodies was due to the absence of the PRB1 product, proteinase B. In the presence of PMSF, wild-type cells accumulated autophagic bodies in the vacuoles under nutrient-deficient conditions, similar to multiple protease-deficient mutants or cells with a disrupted PRB1 gene. The autophagic bodies disappeared rapidly after removal of PMSF, indicating they were an intermediate in the normal autophagic process. The study also showed that autophagic bodies contained cytosolic components, including ribosomes, and that their accumulation was not dependent on the presence of vacuolar proteases. The results suggest that autophagy in yeast is a general response to adverse conditions and that vacuolar proteases are essential for protein turnover under nutrient-deficient conditions. The study provides the first evidence that nutrient-deficient conditions induce extensive autophagic degradation of cytosolic components in yeast vacuoles. The findings support the idea that autophagy is a key mechanism for protein degradation and turnover in yeast under adverse conditions.