ABSTRACT: As a dynamic structure with a barrier between the cell and the outside world, maintenance of cell wall integrity (CWI) is important for fungal growth, development and pathogenicity processes. Here we characterized a MADS-box transcription factor RlmA (AoRlmA) downstream of the CWI regulatory pathway in the nematode-trapping fungus Arthrobotrys oligospora. Deletion of AorlmA caused a reduction in mycelial growth and the number of nuclei, and significant downregulation of transcript levels of genes related to nucleus synthesis and DNA damage repair, such as rad3, spo11, and rad25. Meanwhile, the ΔAorlmA mutant strains showed a significant reduction in spore production compared with the wild-type (WT) strain, and the transcript levels of sporulation-related genes was downregulated in the ΔAorlmA mutant during the early and middle stages of condiation, such as flbA, medA, and vosA. Meanwhile, the mycelial cell wall of the ΔAorlmA mutant strain showed breakage. Also, the transcript levels of genes related to cell wall synthesis were significantly down-regulated in the mutant strain compared to the WT strain, and the mutant strain was more sensitive to stresses of cell wall synthesis disruptors, oxidative stress and osmotic stress than the WT strain. Compared with the WT strain, the ΔAorlmA mutant strain not only had a reduced number of traps and nematicidal ability, but also, the shape of the traps of the mutants has also changed. In addition, In addition, AoRlmA also regulates autophagy and endocytosis. Transcriptome analysis of ΔAorlmA mutant strains showed that AorlmA regulates redox, cell wall synthesis, DNA replication and damage repair, and pathogenic processes. Metabolomic analysis showed that AorlmA is involved in the biosynthesis of secondary metabolites of A. oligospora. To summarise, our data suggest that AorlmA is involved in growth, sporulation, spore germination, maintenance of cell wall integrity, DNA replication and damage repair, pathogenesis, autophagy and secondary metabolite biosynthesis processes.
