AfLaeA, a Global Regulator of Mycelial Growth, Chlamydospore Production, Pathogenicity, Secondary Metabolism, and Energy Metabolism in the Nematode-Trapping Fungus .

Arthrobotrys flagrans () is a typical nematode-trapping fungus which has been used for nematode biocontrol. The global regulator LaeA is widely distributed in filamentous fungi and plays a crucial role in secondary metabolism and development in addition to pathogenicity in fungal pathogens. In this study, the chromosome-level genome of CBS 565.50 was sequenced and homologous sequences of LaeA were identified in . () knockout resulted in slower hyphal growth and a smoother hyphal surface. Importantly, deletion of resulted in the absence of chlamydospores and attenuated glycogen and lipid accumulation in hyphae. Similarly, disruption of the gene led to fewer traps and electron-dense bodies, lower protease activity, and a delay in capturing nematodes. The gene had a large effect on the secondary metabolism of , and both the deletion and overexpression of could yield new compounds, whereas some compounds were lost due to the absence of the . Protein-protein interactions between AfLaeA and another eight proteins were detected. Furthermore, transcriptome data analysis showed that 17.77% and 35.51% of the genes were influenced by the gene on days 3 and 7, respectively. gene deletion resulted in the higher expression level of the gene cluster, and multiple differentially expressed genes involved in glycogen and lipid synthesis and metabolism showed opposite expression patterns in wild-type and Δ strains. In summary, our results provide novel insights into the functions of in mycelial growth, chlamydospore production, pathogenicity, secondary metabolism, and energy metabolism in . The regulation of biological functions, such as the secondary metabolism, development, and pathogenicity of LaeA, has been reported in multiple fungi. But to date, no study on LaeA in nematode-trapping fungi has been reported. Moreover, it has not been investigated whether or not LaeA is involved in energy metabolism and chlamydospore formation has not been investigated. Especially in the formation mechanism of chlamydospores, several transcription factors and signaling pathways are involved in the production of chlamydospores, but the mechanism of chlamydospore formation from an epigenetic perspective has not been revealed. Concurrently, an understanding of protein-protein interactions will provide a broader perspective on the regulatory mechanism of AfLaeA in . This finding is critical for understanding the regulatory role of AfLaeA in the biocontrol fungus and establishes a foundation for developing high-efficiency nematode biocontrol agents.