Comparison of gene expression in trap cells and vegetative hyphae of the nematophagous fungus Monacrosporium haptotylum

Abstract

Nematode-trapping fungi enter the parasitic stage by developing specific morphological structures called traps. The global patterns of gene expression in traps and mycelium of the fungus Monacrosporium haptotylum were compared. The trap of this fungus is a unicellular spherical structure called the knob, which develops on the apex of a hyphal branch. RNA was isolated from knobs and mycelium and hybridized to a cDNA array containing probes of 2822 EST clones of M. haptotylum. Despite the fact that the knobs and mycelium were grown in the same medium, there were substantial differences in the patterns of genes expressed in the two cell types. In total, 23?3 % (657 of 2822) of the putative genes were differentially expressed in knobs versus mycelium. Several of these genes displayed sequence similarities to genes known to be involved in regulating morphogenesis and cell polarity in fungi. Among them were several putative homologues for small GTPases, such as rho1, rac1 and ras1, and a rho GDP dissociation inhibitor (rdi1). Several homologues to genes involved in stress response, protein synthesis and protein degradation, transcription, and carbon metabolism were also differentially expressed. In the last category, a glycogen phosphorylase (gph1) gene homologue, one of the most upregulated genes in the knobs as compared to mycelium, was characterized. A number of the genes that were differentially expressed in trap cells are also known to be regulated during the development of infection structures in plant-pathogenic fungi. Among them, a gas1 (mas3) gene homologue (designated gks1), which is specifically expressed in appressoria of the rice blast fungus, was characterized.

Nematophagous Fungi

“…The global patterns of gene expression has been studied in traps and mycelium of M. haptotylum (Ahre´n et al, 2005). The advantage of using M. haptotylum is that during growth in liquid cultures with heavy aeration, the connection between the traps (knobs) and mycelium can be broken easily and the knobs can be separated from the mycelium by filtration.…”

Proteome of the Nematode-Trapping Cells of the Fungus Monacrosporium haptotylum

“…The trapping cells of nematodetrapping fungi and the appressoria formed by plant-pathogenic fungi have several structural and functional similarities (9). Both are specialized infection structures that develop from hyphae.…”

“…The isolated knobs retain their function as infection structures, i.e., they can trap and kill nematodes (8). A microarray analysis based on a limited set of expressed sequence tag (EST) probes compared the gene expression in knobs with that in vegetative mycelia (9). The result showed that 23% of the genes were differentially expressed; many were homologous to genes involved in the regulation of morphogenesis and cell polarity, stress response, protein synthesis and protein degradation, transcription, and carbon metabolism.…”

Random mutagenesis analysis and identification of a novel C2H2-type transcription factor from the nematode-trapping fungus Arthrobotrys oligospora

“…While 12 nuclei were observed in A. amerospora stained by DAPI, and 6–20 nuclei were observed in A. conoides 8 . In the past 50 years, researchers have made great efforts in identifying pathogenicity-related genes 4–6, 9 , and in understanding the difference between vegetative mycelia and traps 10–13 . Recently, three species of NTF producing different traps were individually sequenced 11, 12, 14 , in which the trap cell proteome of the fungus M. haptotylum 15 , and the proteomic and transcriptional analyses of cell wall related proteins of Arthrobotrys oligospora 16 , were characterized.…”