AoMbp1 interacts with AoSwi6 and plays pleiotropic roles in mycelial development, trap morphogenesis, and stress respone in the nematode-trapping fungus Arthrobotrys oligospora [RNA-Seq]

The fungal specific APSES family proteins involve in regulating fungal growth, development, and multiple biological processes. In this study, AoMbp1, an ortholog of Saccharomyces cerevisiae APSES-type transcription factor Mbp1, was functionally analyzed in a representative nematode-trapping fungus Arthrobotrys oligospora. Inactivation of Aombp1 caused a severe affect on the mycelial growth and development, the mycelial growth rate of ∆Aombp1 mutant was remarkably decreased, the hyphal septa were increased whereas the number of nuclei were significantly reduced, and the lipid droplet accumulation was remarkably increased. Meanwhile, the deletion of Aombp1 resulted a considerable reduction in the number of conidiophores and spore yield, which also caused abnormal spore morphology. In addition, the ∆Aombp1 mutants became more sensitive to several chemical stressors, especially to hyperosmotic reagents. Importantly, disruption of Aombp1 caused the number of traps and nematode-trapping ability were significantly reduced, and most of the traps have changed from their original three-dimensional structure to a planar shape. RNA-Seq, DAP-Seq and Y2H assay showed that AoMbp1 interacted with AoSwi6, and involved in regulating cell cycle, meiosis, lipid metabolism, DNA replication, mismatch repair and nucleotide excision repair. Our study elucidated the functions and potential regulatory mechanism of APSES protein Mbp1 in the mycelial development and trap morphogenesis of nematode-trapping fungi. WT (represented by AO) and ΔAombp1 (represented by AoMbp1) strains were cultured in PD broth at 28℃ with agitation (180 r/min) for 5 days. Mycelia were collected, washed three times with 0.1 M phosphate buffer (pH 6.8–7.2), divided into four groups, and induced with approximately 600 nematodes for 0, 12, and 24 h, respectively; three replicates were used for each sample. RNA was extracted using the AxyPrep Multisource RNA Miniprep Kit (Axygen, Jiangsu, China) and sequenced using the Illumina MiSeq platform at Majorbio Bio-Pharm Technology Co., Ltd. (Shanghai, China). High-throughput sequencingdata were analyzed using the OmicShare online platform.