Fungistatic mechanism of ammonia against nematode- trapping fungus arthrobotrys oligospora, and strategy for this fungus to survive ammonia

• Main Authors: Liu, T. (Author), Long, X. (Author), Mo, M.-H (Author), Tian, D.-W (Author), Xu, J.-P (Author), Yang, Y.-H (Author), Zhang, K.-Q (Author), Zhou, J.-P (Author), Zou, C.-G (Author)
• Format: Article
• Language: English
• Published: American Society for Microbiology 2021
• Subjects: alkalinity; ammonia; Arthrobotrys oligospora; Article; carbon metabolism; conidium; endoplasmic reticulum stress; ER stress; fungal spore germination; fungistatic activity; Fungistatic mechanism; fungus growth; fungus spore; gene knockout; glutamic acid; metabolite; multiomics; Multi-omics; nematophagous fungus; nonhuman; protein homeostasis; protein misfolding; proteome; Soil fungistasis; survival; ubiquitination; unfolded protein response; upregulation; Western blotting
• Online Access: View Fulltext in Publisher

 Soil fungistasis is a phenomenon in which the germination and growth of fungal propagules is widely inhibited in soils. Although fungistatic compounds are known to play important roles in the formation of soil fungistasis, how such compounds act on soil fungi is little studied. In this study, it was found that ammonia (NH3) induced global protein misfolding marked by increased ubiquitination levels of proteins (ubiquitylome data and Western blot verification). The misfolded proteins should trigger the endoplasmic reticulum (ER) stress, which was indicated by electron microscope image and proteome data. Results from the mutants of BiP and proteasome subunit alpha 7 suggested that ER stress played a mechanistic role in inhibiting conidial germination. Results from proteome data indicated that, to survive ammonia fungistasis, conidia first activated the unfolded protein response (UPR) to decrease ER stress and restore ER protein homeostasis, and the function of UPR in surviving ammonia was confirmed by using mutant strains. Second, ammonia toxicity could be reduced by upregulating carbon metabolism-related proteins, which benefited ammonia fixation. The results that metabolites (especially glutamate) could relieve the ammonia fungistasis confirmed this indirectly. Finally, results from gene knockout mutants also suggested that the fungistatic mechanism of ammonia is common for soil fungistasis. This study increased our knowledge regarding the mechanism of soil fungistasis and provided potential new strategies for manipulating soil fungistasis. © 2021 Liu et al.