Regulatory Mechanism of Trap Formation in the Nematode-Trapping Fungi

Abstract

Nematode-trapping (NT) fungi play a significant role in the biological control of plant- parasitic nematodes. NT fungi, as a predator, can differentiate into specialized structures called “traps” to capture, kill, and consume nematodes at a nutrient-deprived condition. Therefore, trap formation is also an important indicator that NT fungi transition from a saprophytic to a predacious lifestyle. With the development of gene knockout and multiple omics such as genomics, transcriptomics, and metabolomics, increasing studies have tried to investigate the regulation mechanism of trap formation in NT fungi. This review summarizes the potential regulatory mechanism of trap formation in NT fungi based on the latest findings in this field. Signaling pathways have been confirmed to play an especially vital role in trap formation based on phenotypes of various mutants and multi-omics analysis, and the involvement of small molecule compounds, woronin body, peroxisome, autophagy, and pH-sensing receptors in the formation of traps are also discussed. In addition, we also highlight the research focus for elucidating the mechanism underlying trap formation of NT fungi in the future.

AMPK Is Involved in Regulating the Utilization of Carbon Sources, Conidiation, Pathogenicity, and Stress Response of the Nematode-Trapping Fungus Arthrobotrys oligospora

“…Of particular interest to nematode-trapping (NT) fungi are the special trapping devices (traps) involved in capturing and killing nematodes ( 13 – 16 ). The traps are specifically formed by the vegetative hyphae of NT fungi, divided into adhesive knobs and columns, adhesive networks, and constricting and nonconstricting rings according to their different predatory methods ( 17 – 19 ). Arthrobotrys oligospora is one of the best-known species of NT fungi, which can develop adhesive networks for nematode predation, and its whole genome has previously been sequenced ( 20 ).…”

SNARE Protein DdVam7 of the Nematode-Trapping Fungus Drechslerella dactyloides Regulates Vegetative Growth, Conidiation, and the Predatory Process via Vacuole Assembly

“…A number of genes involved in multiple signal transduction pathways, nitrate assimilation, intercellular communication, peroxisomes, autophagy, and pH sensing have been investigated in the model trapping fungus A. oligospora . Most of the genes involved in trap morphogenesis also participate in vegetative growth, asexual and sexual reproduction, and virulence ( 22 ). Examples include, Ste12 , Fus3 , and Bck1 in MAPK pathway ( 29 , 30 ), AoAtg8 , AoAtg5 , and AoAtg1 involved in autophagy ( 31 – 33 ), AoPEX1 and AoPEX6 involved in peroxisome biogenesis ( 34 ), and E3-ligase encoding gene AoUBR1 ( 35 ).…”

“…The trap formation is a morphological feature distinct for NTF. Signal transduction pathways and subcellular compounds involved in trap morphogenesis have been studied in the adhesive net-forming fungus Arthrobotrys oligospora , such as the G-protein signaling pathway, the mitogen-activated protein kinase (MAPK) signaling pathway, the cAMP-protein kinase A signaling pathway, the Ca 2+ -related signaling pathway, and the Woronin body, autophagy, and peroxisomes ( 22 ). However, the roles of SNAREs in trap morphogenesis in NTF remain poorly understood.…”

The Arf-GAP Proteins AoGcs1 and AoGts1 Regulate Mycelial Development, Endocytosis, and Pathogenicity in Arthrobotrys oligospora

“…Extracellular serine proteases are significant pathogenic factors in A. oligospora and other NT fungi during their infection of nematodes [ 26 , 27 , 28 ]. Since the genome of A. oligospora was sequenced in 2011, studies have focused on regulating mycelial growth, development, and pathogenicity of A. oligospora [ 29 , 30 , 31 , 32 , 33 , 34 , 35 ].…”