Purpureocillium lavendulum is a fungus with promising biocontrol applications. Here, transcriptome data acquired during the infection of Caenorhabditis elegans by Purpureocillium lavendulum showed that the transcription of metabolite synthesis genes was significantly up-regulated after 24 and 48 h of the fungus-nematode interaction. Then, the up-regulated transcription level of lipoxygenase was confirmed by RT-qPCR. The ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis of differential metabolites revealed that this interaction resulted in the emergence of new metabolites or enhanced the production of metabolites. The results of the UPLC-MS analysis and the nematicidal assay were used to establish optimal culturing conditions under which 12 metabolites, including 3 hydroxylated C18 fatty acids and 9 steroids, were isolated and identified. Among them, hydroxylated fatty acids showed pronounced nematicidal activity against Meloidogyne incognita, and two degradative sterols showed chemotaxis activity to M. incognita. This study lays a foundation for the function of lipoxygenase and its products during the infection of Purpureocillium lavendulum.

Purpureocillium lavendulum is a biological control agent with several registered products that can parasitize the eggs and larvae of various pathogenic nematodes. In this study, the pathogenicity and secondary metabolites of the fungus P. lavendulum YMF1.00683 were investigated. The strain YMF1.00683 had infection efficiency against the plant root-knot nematode Meloidogyne incognita. The strain’s process of infecting nematodes was observed under a microscope. Moreover, seven metabolites, including a new sterol (1), were isolated and identified from cultures of YMF1.0068 in Sabouraud’s dextrose agar. A bioassay showed that 5-methoxymethyl-1H-pyrrole-2-carboxaldehyde (7) is toxic to M. incognita and affects the egg hatching. It caused 98.23% mortality in M. incognita and could inhibit 80.78% of the hatching eggs at 400 μg/mL over a period of 96 h. Furthermore, 5-methoxymethyl-1H-pyrrole-2-carboxaldehyde (7) showed a strong avoidance effect at 40 ppm, and its chemotactic index value was −0.37. The results indicate that P. lavendulum could produce active metabolites against M. incognita.