Intercellular communication is required for trap formation in the nematode-trapping fungus Duddingtonia flagrans

Abstract

Nematode-trapping fungi (NTF) are a large and diverse group of fungi, which may switch from a saprotrophic to a predatory lifestyle if nematodes are present. Different fungi have developed different trapping devices, ranging from adhesive cells to constricting rings. After trapping, fungal hyphae penetrate the worm, secrete lytic enzymes and form a hyphal network inside the body. We sequenced the genome of Duddingtonia flagrans , a biotechnologically important NTF used to control nematode populations in fields. The 36.64 Mb genome encodes 9,927 putative proteins, among which are more than 638 predicted secreted proteins. Most secreted proteins are lytic enzymes, but more than 200 were classified as small secreted proteins (< 300 amino acids). 117 putative effector proteins were predicted, suggesting interkingdom communication during the colonization. As a first step to analyze the function of such proteins or other phenomena at the molecular level, we developed a transformation system, established the fluorescent proteins GFP and mCherry, adapted an assay to monitor protein secretion, and established gene-deletion protocols using homologous recombination or CRISPR/Cas9. One putative virulence effector protein, PefB, was transcriptionally induced during the interaction. We show that the mature protein is able to be imported into nuclei in Caenorhabditis elegans cells. In addition, we studied trap formation and show that cell-to-cell communication is required for ring closure. The availability of the genome sequence and the establishment of many molecular tools will open new avenues to studying this biotechnologically relevant nematode-trapping fungus.

Nematode-Trapping Fungi Produce Diverse Metabolites during Predator–Prey Interaction

“…Specifically, NTF in response to the lifestyle switch enrich the production of thousands of metabolites, containing hundreds of structural families, as revealed by molecular networking. Our results and previous studies have collectively shown that the lifestyle switching of NTF is accompanied by physiological changes in transcriptome [7,8], proteome [7], and metabolome. Furthermore, such changes in the metabolome exhibit species-specificity.…”

“…The underlying physiochemical processes in developing the trapping devices are of great interest in biological research. Studies on genomic, transcriptomic, and proteomic aspects have collectively shown that the trap formation is associated with the upregulation of multiple signal transduction pathways, biosynthesis of adhesive proteins [7], intercellular communication [8], and nitrate assimilation [9]. On the other hand, little is known about the metabolome of NTF.…”

Natural diversity in the predatory behavior facilitates the establishment of a new robust model strain for nematode-trapping fungi

“…However, only recently have the molecular mechanisms underlying the singular biology of these specialized predators began to be uncovered. For example, a recent work has generated a strain lacking the signaling scaffold protein Soft and shown that cell-cell fusion is required for ring closure in Duddingtonia flagrans (41). In A. oligospora , ATCC24927-background trapping-deficient mutants have been isolated: adhesin protein Mad1 (42), autophagy protein Atg8 (43), mitogen-activated protein kinase Slt2 (44), pH sensor PalH (45), NADPH oxidase NoxA (46), low-affinity calcium uptake system proteins Fig1 and Fig2 (47), Rab GTPase Rab7A (48), actin-associated protein Crn1 (49), Woronin body component Hex1 (50), malate synthase Mls (51), glycogen phosphorylase Gph1 (52), transcription factors VelB (53) and StuA (54), and microRNA processing protein Qde2 (55), to which we add the G-protein β subunit Gpb1.…”

Stimulating Duddingtonia flagrans chlamydospore production through dehydration

“…A few limitations of the use of D. flagrans include the necessity of cell-cell signaling in trap formation and constriction that requires hyphal fusion and a significant mycelial growth to achieve a switch from saprotrophic to zootrophic nutrition intake (Youssar et al 2019). This denotes a requirement of a certain threshold chlamydospore administration to cause sufficient growth for this transformation.…”