Abstract
Hog1, a mitogen-activated protein kinase (MAPK), has been identified in diverse fungal species, and it regulates various cellular processes, such as osmoadaptation, nutrient-sensing, and pathogenesis. However, the roles that Hog1 plays in nematode-trapping fungi were previously unclear. Here, we characterized orthologs of Saccharomyces cerevisiae Hog1 and membrane mucin Msb2 in the nematode-trapping fungus Arthrobotrys oligospora. We generated gene deletion mutants of HOG1 and MSB2 in A. oligospora, and characterized their roles in osmosensing, growth, and trap morphogenesis. We found that both hog1 and msb2 mutants were highly sensitive to high osmolarity. Predation analyses further revealed that hog1 and msb2 deletion caused a reduction in trap formation and predation efficiency. Furthermore, HOG1 is required for conidiation in A. oligospora, demonstrating its critical role in this developmental pathway. In summary, this study demonstrated that the conserved Hog1 and Msb2 govern physiology, growth and development in the nematode-trapping fungus A. oligospora.
Highlights
The ability to sense and respond appropriately to the environmental changes is essential for any organism
We investigated the roles of Hog1 mitogen-activated protein kinase (MAPK) pathway in Arthrobotrys oligospora, one of the most common and best understood species of nematode-trapping fungi (NTF) [22]
The high osmolarity glycerol (HOG) MAPK pathway is important in regulating responses to hyperosmotic stress in fungi [2], so we investigated the effect of treating our A. oligospora hog1 and masb2 mutants with excess sodium chloride (NaCl)
Summary
The ability to sense and respond appropriately to the environmental changes is essential for any organism. One of the best-studied MAPK pathways is the high osmolarity glycerol (HOG) pathway in the model yeast S. cerevisiae, which responds to changes in external osmolarity. MAPK pathway is mainly involved in osmoregulation in S. cerevisiae, its orthologs in various other fungi often exert additional biological functions [2,10]. We investigated the roles of Hog MAPK pathway in Arthrobotrys oligospora, one of the most common and best understood species of NTF [22]. We demonstrate that both Hog and Msb are involved in the pathogenicity, and that Hog is required for conidiation. We speculate that additional upstream osmosensors, which are functionally redundant to Msb, regulate Hog activation. The Hog MAPK pathway appears to be important for the predator–prey interactions between NTF and nematodes
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