Autophagy is a cellular degradation process that recycles the cytoplasmic components among eukaryotes.Although it has been intensively studies in yeast,plants and mammals,its function in microalgae remains mostly unknown.Chlorella protothecoides is a green microalga that has the ability to grow either autotrophically under light or heterotrophically in media containing glucose.The two growth modes are inter-convertible,accompanied by drastic changes in morphology and cellular composition,and the underlying mechanisms have not been elucidated.