Abstract
Autophagy plays an important role in cell growth and development. The autophagy-related gene atg4 encodes a cysteine protease, which can cleave the carboxyl terminus of Atg8, thus plays a role in autophagosome formation in yeast and filamentous fungi. Arthrobotrys oligospora is well known for producing special trapping-devices (traps) and capturing nematodes. In this study, two ΔAolatg4 mutants were generated using targeted gene replacement and were used to investigate the biological functions of autophagy in A. oligospora. Autophagic process was observed using the AoAtg8-GFP fusion protein. The mutants showed a defective in hyphal growth and sporulation and were sensitive to chemical stressors, including menadione and Congo red. The spore yield of the ΔAolatg4 mutants was decreased by 88.5% compared to the wild type (WT), and the transcript levels of six sporulation-related genes, such as abaA, fluG, brlA, and wetA, were significantly downregulated during the conidiation stage. Deletion of Aolatg4 also affected the cell nuclei and mycelial septal development in A. oligospora. Importantly, autophagosome formation and the autophagic process were impaired in the ΔAolatg4 mutant. Moreover, the ΔAolatg4 mutant lost its ability to form mature traps. Our results provide novel insights into the roles of autophagy in A. oligospora.
Highlights
Autophagy is a conserved intracellular recycling process in all eukaryotic cells, in which autophagosomes are delivered to lysosomes or vacuoles for degradation (Reggiori and Klionsky, 2002; Nakatogawa et al, 2012; Ryter et al, 2013)
Our results suggest that Aolatg4 plays important roles in autophagic process, and regulates hyphal growth, conidiation, stress response, and trap formation in A. oligospora
Atg4 orthologs from diverse fungi was divided into two clades (A and B); Atg4 orthologs from three species of NT fungi clustered into clade B, and Atg4 from other filamentous fungi clustered into clade A (Supplementary Figure S1)
Summary
Autophagy is a conserved intracellular recycling process in all eukaryotic cells, in which autophagosomes are delivered to lysosomes or vacuoles for degradation (Reggiori and Klionsky, 2002; Nakatogawa et al, 2012; Ryter et al, 2013). The autophagic process is governed by autophagy-related (Atg) proteins, which orchestrate the different steps of autophagy, and about 19 Atg proteins are necessary for autophagosome formation (Farré and Subramani, 2016). AolAtg Regulates Autophagosome Formation autophagy-related structures, it can be used a reliable marker for autophagy (Hirata et al, 2017). Atg plays a vital role in autophagy by cleaving the Atg8-PE, which will help to recycle Atg for the round of the conjugation reaction (Nakatogawa et al, 2007, 2012), and promote the elongation step of the isolation membrane directly (Hirata et al, 2017)
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