SNARE Protein AoSec22 Orchestrates Mycelial Growth, Vacuole Assembly, Trap Formation, Stress Response, and Secondary Metabolism in Arthrobotrys oligospora

Abstract

Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) facilitate intracellular vesicle trafficking and membrane fusion in eukaryotes and play a vital role in fungal growth, development, and pathogenicity. However, the functions of SNAREs are still largely unknown in nematode-trapping fungi. Arthrobotrys oligospora is a representative species of nematode-trapping fungi that can produce adhesive networks (traps) for nematode predation. In this study, we characterized AoSec22 in A. oligospora, a homolog of the yeast SNARE protein Sec22. Deletion of Aosec22 resulted in remarkable reductions in mycelial growth, the number of nuclei, conidia yield, and trap formation, especially for traps that failed to develop mature three-dimensional networks. Further, absence of Aosec22 impaired fatty acid utilization, autophagy, and stress tolerance; in addition, the vacuoles became small and fragmented in the hyphal cells of the ∆Aosec22 mutant, and large vacuoles failed to form. The reduced sporulation capacity correlated with the transcriptional repression of several sporulation-related genes, and the impaired accumulation of lipid droplets is in line with the transcriptional repression of several genes involved in fatty acid oxidation. Moreover, absence of Aosec22 remarkably impaired secondary metabolism, resulting in 4717 and 1230 compounds upregulated and downregulated in the ∆Aosec22 mutant, respectively. Collectively, our data highlighted that the SNARE protein AoSec22 plays a pleiotropic role in mycelial growth and development, vacuole assembly, lipid metabolism, stress response, and secondary metabolism; in particular, it is required for the proper development of traps in A. oligospora.

AoSte12 Is Required for Mycelial Development, Conidiation, Trap Morphogenesis, and Secondary Metabolism by Regulating Hyphal Fusion in Nematode-Trapping Fungus Arthrobotrys oligospora

“…In addition, phospholipase PldA is required for polarized growth and cell fusion in E. festucae ( 51 ), and PlaA regulates conidiation, appressorial turgor pressure, and pathogenicity in M. oryzae ( 52 ). The ortholog of SNARE domain protein (AOL_s00188g92) mediates vesicle membrane fusion with target compartments ( 53 ), and vesicle transport protein Sec22 is involved in regulating cell wall integrity, growth, reproduction, pathogenicity, the regulation of ROS, and the expression of extracellular enzymes in filamentous fungi ( 54 ).…”

p21-activated kinase is involved in the sporulation, pathogenicity, and stress response of Arthrobotrys oligospora under the indirect regulation of Rho GTPase-activating protein

“…Three fragments were inserted into the pRS426 plasmid to form a fusion vector. The recombinant fragments were amplified by PCR and transformed into A. oligospora protoplasts in a PEG-mediated manner, as described previously ( Tunlid et al, 1999 ; Zhu et al, 2023 ). Transformants were cultured on PDAS medium with 200 μg/mL hygromycin B and verified by PCR, and positive transformants were further confirmed by Southern blot analysis according to the instructions of the North2South Chemiluminescent Hybridization Detection Kit (Pierce, Rockford, United States).…”

Involvement of AoMdr1 in the Regulation of the Fluconazole Resistance, Mycelial Fusion, Conidiation, and Trap Formation of Arthrobotrys oligospora

“…The stress responses of the WT and ∆ Aomdr1 mutants to chemical stressors were assessed in a TG medium supplemented with a cell-wall-perturbing agent (sodium dodecyl sulfate (SDS)) and osmotic agents (NaCl and sorbitol) for 5 days at 28 °C [ 36 ]. To test the fungal response to heat shock, the fungal strains were incubated on a TYGA plate for 2 days, then transferred into 28, 32, 36, and 40 °C conditions, respectively, for 6 h post-incubation, then moved to 28 °C conditions to continue incubation for a total of 5 days [ 37 ].…”