Kikuma_2011_FEMS.Microbiol.Lett_316_61

Autophagy is a degradation system in which cellular components are digested via vacuoles/lysosomes, and involved in differentiation in addition to helping cells to survive starvation. The autophagic process is composed of several steps: induction of autophagy, formation of autophagosomes, transportation to vacuoles, and degradation of autophagic bodies. To further understand autophagy in the filamentous fungus Aspergillus oryzae, we first constructed A. oryzae mutants defective for the Aoatg13, Aoatg4, and Aoatg15 genes and examined the resulting phenotypes. The deltaAoatg13 mutant developed conidiophores and conidia, although the number of conidia was decreased compared with the wild-type strain, while conidiation in the deltaAoatg4 and deltaAoatg15 mutants was not detected. The deltaAoatg15 mutants displayed a marked reduction of development of aerial hyphae. Moreover, autophagy in these mutants was examined by observation of the behavior of enhanced green fluorescent protein (EGFP)-AoAtg8. In the deltaAoatg13 mutant, the slight accumulation of EGFP-AoAtg8 in vacuoles, preautophagosomal structures (PAS), and autophagosomes was observed, whereas only PAS-like structures were detected in the deltaAoatg4 mutant. In the deltaAoatg15 mutant, autophagic bodies accumulated in vacuoles, suggesting that the uptake process proceeded. We therefore propose that the level of autophagy is closely correlated with the degree of differentiation in A. oryzae.