Aolatg1 and Aolatg13 Regulate Autophagy and Play Different Roles in Conidiation, Trap Formation, and Pathogenicity in the Nematode-Trapping Fungus Arthrobotrys oligospora

Abstract

Autophagy is a conserved cellular recycling and trafficking pathway in eukaryotes that plays an important role in cell growth, development, and pathogenicity. Atg1 and Atg13 form the Atg1–Atg13 complex, which is essential for autophagy in yeast. Here, we characterized the roles of the Aolatg1 and Aolatg13 genes encoding these autophagy-related proteins in the nematode-trapping fungus Arthrobotrys oligospora. Investigation of the autophagy process by using the AoAtg8-GFP fusion protein showed that autophagosomes accumulated inside vacuoles in the wild-type (WT) A. oligospora strain, whereas in the two mutant strains with deletions of Aolatg1 or Aolatg13, GFP signals were observed outside vacuoles. Similar results were observed by using transmission electron microscopy. Furthermore, deletion of Aolatg1 caused severe defects in mycelial growth, conidiation, conidial germination, trap formation, and nematode predation. In addition, transcripts of several sporulation-related genes were significantly downregulated in the ΔAolatg1 mutant. In contrast, except for the altered resistance to several chemical stressors, no obvious differences were observed in phenotypic traits between the WT and ΔAolatg13 mutant strains. The gene ontology analysis of the transcription profiles of the WT and ΔAolatg1 mutant strains showed that the set of differentially expressed genes was highly enriched in genes relevant to membrane and cellular components. The Kyoto Encyclopedia of Genes and Genomes analysis indicated that differentially expressed genes were highly enriched in those related to metabolic pathways, autophagy and autophagy-related processes, including ubiquitin-mediated proteolysis and SNARE interaction in vesicular transport, which were enriched during trap formation. These results indicate that Aolatg1 and Aolatg13 play crucial roles in the autophagy process in A. oligospora. Aolatg1 is also involved in the regulation of asexual growth, trap formation, and pathogenicity. Our results highlight the importance of Aolatg1 in the growth and development of A. oligospora, and provide a basis for elucidating the role of autophagy in the trap formation and pathogenicity of nematode-trapping fungi.

AMPK Is Involved in Regulating the Utilization of Carbon Sources, Conidiation, Pathogenicity, and Stress Response of the Nematode-Trapping Fungus Arthrobotrys oligospora

“…After 3 days of incubation, equal amounts of nematodes were added for induction for 0 and 12 h, and mycelia were collected. Three independent biological replicates were used for each sample, and hyphal samples (12 samples) were sent to the Shanghai Meiji Biological Company (Shanghai, China) for RNA sequencing and analysis ( 65 ). GO and KEGG analyses were performed using the free online Majorbio Cloud Platform ( http://www.majorbio.com ).…”

AoSsk1, a Response Regulator Required for Mycelial Growth and Development, Stress Responses, Trap Formation, and the Secondary Metabolism in Arthrobotrys oligospora

“…The number of autophagosomes and LDs was remarkably reduced in the hyphal cells of the Δ Aossk1 mutant, whereas their volumes were considerably larger than those in the WT strain. Recently, several autophagy-related genes, such as atg1 , atg4 , and atg5 , have been shown to play an indispensable role in conidiation and trap formation in A. oligospora [ 36 , 43 , 44 ]. In addition, the deletion of Aossk1 inhibited endocytosis and reduced the number of autophagic vacuoles.…”

“…Meanwhile, it affects the production of secondary metabolites. In addition, AoSsk1 can regulate multiple stress responses, including responses to osmotic stress and oxidative stress, and oxidative stress has been closely associated with conidiation and virulence in fungi [ 44 , 52 ]. Therefore, A. oligospora can respond to extracellular signals, such as nematodes and various stressors, by AoSsk1 and the Hog1 signaling pathway, and can regulate mycelial growth, trap formation, and lifestyle transitions.…”

The cAMP‐PKA signalling pathway regulates hyphal growth, conidiation, trap morphogenesis, stress tolerance, and autophagy in Arthrobotrys oligospora

“…Traps of NT fungi are key devices for nematode predation, and trap morphogenesis is a sophisticated process regulated by diverse cellular processes, such as signal transduction (Wang et al, 2022;Xie et al, 2022b;Zhu et al, 2022), energy metabolism (Yang et al, 2011), small molecule compounds (Stadler et al, 1993;Wei et al, 2011;Yu et al, 2021), Woronin body (Liang et al, 2017), peroxisome (Liu et al, 2022), autophagy (Zhou et al, 2020(Zhou et al, , 2022a(Zhou et al, , 2022b, and cell communication (Youssar et al, 2019). In this study, signal transduction, energy metabolism, small molecule metabolism, and redox-related processes were also enriched in KEGG and GO analyses of the transcriptome (Figure 6C,D).…”