Nucleophagy in Aspergillus oryzae is Mediated by Autophagosome Formation and Vacuole-Mediated Degradation

TL;DR

This study shows that whole nuclei are degraded through autophagy in the fungus Aspergillus oryzae, involving autophagosome formation and vacuole-mediated breakdown.

Contribution

The study demonstrates that entire nuclei are engulfed by autophagosomes and degraded in vacuoles in A. oryzae.

Findings

Histone H2B-EGFP degradation was significantly reduced in ΔAoypt7 and ΔAoatg15 mutants under starvation.

Autophagosomes and autophagic bodies surrounding whole nuclei accumulated in ΔAoypt7 and ΔAoatg15 mutants.

Nuclei are engulfed as a whole in autophagosomes and degraded in the vacuolar lumen.

Abstract

We previously reported autophagy-mediated degradation of nuclei, nucleophagy, in the filamentous fungus Aspergillus oryzae. In this study, we examined whether nuclei are degraded as a whole. We generated A. oryzae mutants deleted for orthologs of Saccharomyces cerevisiae YPT7 and ATG15 which are required, respectively, for autophagosome-vacuole fusion and vacuolar degradation of autophagic bodies. Degradation of histone H2B-EGFP under starvation conditions was greatly decreased in the ΔAoypt7 and ΔAoatg15 mutants. Fluorescence and electron microscopic observations showed that autophagosomes and autophagic bodies surrounding the entire nuclei were accumulated in the cytoplasm of ΔAoypt7 and the vacuole of ΔAoatg15, respectively. These results indicate that nuclei are engulfed in the autophagosomes as a whole and transported/released into the vacuolar lumen where they are degraded.

The online version contains supplementary material available at 10.1007/s00284-024-03838-y.

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