Adhesive Knobs Research Articles

DHXT1, a Virulence Factor of Dactylellina haptotyla, Regulates Pathogenicity by Participating in Trap Formation and Metabolite Synthesis.

The capsule-associated protein 10 gene (CAP10) is indispensable due to its involvement in pod formation and virulence maintenance in Cryptococcus neoformans. The function of the CAP10 gene in nematode-predatory fungi remains unreported. As a typical nematode-trapping fungus, Dactylellina haptotyla efficiently captures nematodes using adhesive knobs, which has potential applications in the biological control of plant-parasitic nematodes. In this study, we investigated the function of DHXT1 (a CAP10 homologous protein) in D. haptotyla-nematode interactions based on the disruption and overexpression of DHXT1, phenotypic analysis and metabolomic analysis. As a result, it was shown that the disruption of the DHXT1 gene causes a marked decrease in the number of adhesive knobs, and on the contrary, the overexpression of the DHXT1 gene causes a substantial increase in the number of adhesive knobs. Interestingly, the variety of metabolites increased with the disruption of the DHXT1 and decreased with the overexpression of the DHXT1 gene. The results suggest that DHXT1 effects pathogenicity through its involvement in adhesive knobs' formation and metabolite synthesis and serves as a key virulence factor in D. haptotyla.

Evaluation of nematophagous and biocontrol efficacy of Dactylellina phymatopaga against Meloidogyne graminicola on rice (Oryza sativa L.)

Dactylellina phymatopaga is a nematode-trapping fungus which traps, kills and parasitizes nematodes. The rice root-knot nematode, Meloidogyne graminicola, is an important plant-parasitic nematode that threatens rice production worldwide. Therefore, it is most important to find new substitute for chemical control of M. graminicola. The present study aimed to investigate the in vitro trapping, germination and nematophagous ability in soil and fungus efficacy to reduce the number and biomass of developing stages of M. graminicola in rice roots. Isolates of D. phymatopaga were found to produced sessile adhesive knobs on growing hypahe to trap and paralyze M. graminicola J2 up to 98.8 % within 120 h of inoculation, in in-vitro conditions. Test for germination and nematophagous activities in various soils showed that spores of D. phymatopaga frequently germinate in soil with formation of adhesive sessile knobs on their germ lings, capturing and parasitizing nearby free living nematodes. Application of D. phymatopaga in M. graminicola-infested soil at the time and prior to rice sowing showed significant reduction in the number of root galls, number and biomass of developing stages of M. graminicola in rice roots (62.65–80.73 %) increasing plant health as compared to plants grown in nematode infested soil. Application of D. phymatopaga 7 days before sowing showed the highest biocontrol ability by decreasing in the nematode biomass in the associated rice roots per plant and the expended nematode-to-root biomass ratio (NB:RB). The results showed that the nematode-trapping behavior of D. phymatopaga yields a bio-management potential in reducing the number of developing stages of M. graminicola and their biomass in rice roots.

Secondary Metabolites from the Nematode-Trapping Fungus Dactylellina haptotyla YMF1.03409.

As a representative nematode-trapping fungus, Dactylellina haptotyla can capture and kill nematodes by producing traps, known as adhesive knobs. In this paper, the strain of D. haptotyla YMF1.03409 was studied by means of medium screening, fermentation, and purification and identification of crude extracts. Eighteen compounds were obtained from D. haptotyla YMF1.03409, including two new metabolites, nosporins C (1) and D (2). The known metabolites were identified to be 3-chloro-4-methoxybenzaldehyde (3), 3-chloro-4-methoxybenzoic acid (4), 2-chloro-1-methoxy-4-(methoxymethyl)benzene (5), 3-hydroxy-3-methyloxindole (6), nicotinic acid (7), succinic acid (8), 3,4-dihydroxybutanoic acid (9), 5'-O-methyladenosine (10), uridine (11), 2'-deoxyuridine (12), thymidine (13), 3-(phenylmethyl)-2,5-morpholinedione (14), methyl-β-D-glucopyranoside (15), 1,2-benzenedicarboxylic acid bis(2-methyl heptyl) ester (16), β-sitosterol (17), and 3β,6α-diol-stigmastane (18). The bioactive assay showed that these compounds had no obvious nematicidal activity against the nematodes Meloidogyne incognita and Panagrellus redivivus.

A particle-based computational model to analyse remodelling of the red blood cell cytoskeleton during malaria infections.

Red blood cells can withstand the harsh mechanical conditions in the vasculature only because the bending rigidity of their plasma membrane is complemented by the shear elasticity of the underlying spectrin-actin network. During an infection by the malaria parasite Plasmodium falciparum, the parasite mines host actin from the junctional complexes and establishes a system of adhesive knobs, whose main structural component is the knob-associated histidine rich protein (KAHRP) secreted by the parasite. Here we aim at a mechanistic understanding of this dramatic transformation process. We have developed a particle-based computational model for the cytoskeleton of red blood cells and simulated it with Brownian dynamics to predict the mechanical changes resulting from actin mining and KAHRP-clustering. Our simulations include the three-dimensional conformations of the semi-flexible spectrin chains, the capping of the actin protofilaments and several established binding sites for KAHRP. For the healthy red blood cell, we find that incorporation of actin protofilaments leads to two regimes in the shear response. Actin mining decreases the shear modulus, but knob formation increases it. We show that dynamical changes in KAHRP binding affinities can explain the experimentally observed relocalization of KAHRP from ankyrin to actin complexes and demonstrate good qualitative agreement with experiments by measuring pair cross-correlations both in the computer simulations and in super-resolution imaging experiments.

Comparative Analyses of Mitochondrial Genomes Provide Evolutionary Insights Into Nematode-Trapping Fungi.

Predatory fungi in Orbiliaceae (Ascomycota) have evolved a diversity of trapping devices that enable them to trap and kill nematodes, other small animals, and protozoans. These trapping devices include adhesive hyphae, adhesive knobs, adhesive networks, constricting rings, and non-constricting rings. Their diversity and practical importance have attracted significant attention from biologists, making them excellent model organisms for studying adaptative evolution and as biological control agents against parasitic nematodes. The putative origins and evolutionary relationships among these carnivorous fungi have been investigated using nuclear protein-encoding genes, but their patterns of mitogenome relationships and divergences remain unknown. Here we analyze and compare the mitogenomes of 12 fungal strains belonging to eight species, including six species representing all four types of nematode trapping devices and two from related but non-predatory fungi. All 12 analyzed mitogenomes were of circular DNA molecules, with lengths ranging from 146,101 bp to 280,699 bp. Gene synteny analysis revealed several gene rearrangements and intron transfers among the mitogenomes. In addition, the number of protein coding genes (PCGs), GC content, AT skew, and GC skew varied among these mitogenomes. The increased number and total size of introns were the main contributors to the length differences among the mitogenomes. Phylogenetic analyses of the protein-coding genes indicated that mitochondrial and nuclear genomes evolved at different rates, and signals of positive selection were found in several genes involved in energy metabolism. Our study provides novel insights into the evolution of nematode-trapping fungi and shall facilitate further investigations of this ecologically and agriculturally important group of fungi.

The complete mitochondrial genomes of the nematode-trapping fungus Dactylellina cionopaga

Dactylellina cionopaga is a nematophagous fungus known to form unstalked adhesive knobs and simple two-dimension networks. In our study, we sequenced almost complete mitochondrial genome of D. cionopaga. The mitogenome has 194,125 base pairs with a GC content of 26.59% and made up of total of 32 genes (14 protein-coding genes, 16 transfer RNAs genes, and two ribosomal RNAs genes). The complete mitogenome of D. cionopaga will provide potential genetic resources for further evolutionary studies of this species.

Nematode-Trapping Fungi

Nematode-trapping fungi are a unique and intriguing group of carnivorous microorganisms that can trap and digest nematodes by means of specialized trapping structures. They can develop diverse trapping devices, such as adhesive hyphae, adhesive knobs, adhesive networks, constricting rings, and nonconstricting rings. Nematode-trapping fungi have been found in all regions of the world, from the tropics to Antarctica, from terrestrial to aquatic ecosystems. They play an important ecological role in regulating nematode dynamics in soil. Molecular phylogenetic studies have shown that the majority of nematode-trapping fungi belong to a monophyletic group in the order Orbiliales (Ascomycota). Nematode-trapping fungi serve as an excellent model system for understanding fungal evolution and interaction between fungi and nematodes. With the development of molecular techniques and genome sequencing, their evolutionary origins and divergence, and the mechanisms underlying fungus-nematode interactions have been well studied. In recent decades, an increasing concern about the environmental hazards of using chemical nematicides has led to the application of these biological control agents as a rapidly developing component of crop protection.

Lecophagus vermicola sp. nov., a nematophagous hyphomycete with an unusual hunting strategy

Lecophagus vermicola sp. nov. is described and illustrated as a predacious (carnivorous) hyphomycete living in bark fissures of living trees of Platanus and other angiosperm and gymnosperm trees, recorded in Hungary, Luxembourg and France. The fungus captures nematodes unlike other Lecophagus species, which are predators of rotifers and tardigrades. The morphology of the sessile, adhesive knobs differ from all previously described species of the genus which form adhesive pegs. Molecular data confirms that the new species belongs to the Lecophagus clade but without matching existing sequences. The fungus captures victims with adhesive knobs and colonizes its prey with a mycelium of rather broad hyphae on which, again, adhesive knobs are formed which penetrate the cuticule of the victim. Clusters of colonized nematodes form a network utilized to capture more prey. The fungus lives in the xeric, ephemerally aquatic habitat of bark fissures of standing, living or dead, corticated trunks and branches. The genus Haptocara is compared, which has similar adhesive knobs capturing nematodes and similar broad hyphae, but for which no molecular data was available.

Induction of trap formation in nematode-trapping fungi by bacteria-released ammonia.

A total of 11 bacterial strains were assayed for bacteria-induced trap formation in the nematode-trapping fungus Arthrobotrys oligospora YMF1·01883 with two-compartmented Petri dish. These strains were identified on the basis of their 16S rRNA gene sequences. Volatile organic compounds (VOCs) of eight isolates were extracted using solid-phase micro-extraction (SPME) and their structures were identified based on gas chromatography-mass spectrometry (GC-MS). At the same time, all isolates were used for quantitative measurement of ammonia by the indophenol blue method. The effects of pure commercial compounds on inducement of trap formation in A.oligospora were tested. Taken together, results demonstrated that the predominant bacterial volatile compound inducing trap formation was ammonia. Meanwhile, ammonia also played a role in other nematode-trapping fungi, including Arthrobotrys guizhouensis YMF1·00014, producing adhesive nets; Dactylellina phymatopaga YMF1·01474, producing adhesive knobs; Dactylellina cionopaga YMF1·01472, producing adhesive columns and Drechslerella brochopaga YMF1·01829, producing constricting rings.

Zygomycetes: an emerging problem in the clinical laboratory.

This supplement of ‘Mycoses’ is devoted to infections caused by a group of fungi traditionally known as the zygomycetes. The Zygomycota represent an important group of medically important opportunistic fungi, which cause devastating fungal infections in humans and animals with severe underlying immune or metabolic disorders. These infections are increasing in numbers due to the growing populations of patients with uncontrolled diabetes and immunosuppression, as well as the increased use of prophylactic measures against other hospital infections using drugs that are ineffective against Zygomycota organisms. The Zygomycota has been one of the ancestral phyla in the fungal Kingdom. The second class, the Trichomycetes contains phylogenetically diverged groups of organisms united based on their ecological requirement as endocommensals in the digestive tract of the aquatic insect larvae or other arthropods. Under the influence of molecular phylogeny the Zygomycota as a distinct phylum has changed significantly over the past decades. The group disintegrated into the five subphyla of Entomophthoromycotina, Kickxellomycotina, Mortierellomycotina, Mucoromycotina and Zoopagomycotina. These subphyla are too distantly related from each other to compose a single group higher up in the hierarchy. These changes have little impact on medical mycology, since just the umbrella term has disappeared and the major types of mycoses are still distinguishable into: (i) the preponderantly chronic entomophthoromycoses; (ii) the rapidly progressive mucormycoses; and (iii) the few representatives of Mortierellomycotina causing bovine abortion. Clinical parameters in main traits coincide with the above taxonomic and phylogenetic tripartition. The Mucorales is by far the largest order of the lower fungi, with nearly 240 species in 48 genera. In the interest of nomenclatural stability, common generic names such as Mucor and Rhizopus were preserved as presently applied. In their natural habitat the fungi comprise a wide morphological and ecological diversity as saprobes or opportunistic pathogens. The Mucorales are generalistic fungi having importance as biotransforming agents of pharmacological and chemical compounds and are extensively used in the food industry. The same, thermotolerant species – mostly belonging to the genera Lichtheimia, Rhizomucor and Rhizopus – are found to occur as agents of infection. This remarkable duality of good and bad united in the same individual must be explained by properties needed in their natural habitat, which are as yet only fragmentarily understood. The Mucorales are cosmopolitan, and are amongst the most widespread fungi, but regional differences exist in prevalence between different patient populations. The Entomophthorales is an order of mainly pathogenic fungi on insects with highly adapted killing mechanisms. Spores are actively discharged to become airborne and are adhesive knobs to invade between segments of the host's abdomen. These fungi are obviously not adapted to human infection, but nevertheless severe systemic infections in sinus and gastrointestinal tract have frequently been reported from the tropics caused by species found in the intestinal tract of cold-blooded vertebrates. Only limited numbers of species in the genera Basidiobolus and Conidiobolus are involved. This special issue touches numerous aspects of opportunism in Mucorales and Entomophthorales, ranging from clinical aspects and different patient populations to taxonomy and virulence studies.

Metabolites from Carnivorous Fungus Arthrobotrys entomopaga and Their Functional Roles in Fungal Predatory Ability

The carnivorous fungus Arthrobotrys entomopaga (Drechsler) can develop adhesive knobs to capture nematodes. Chemical study on the culture medium of A. entomopaga producing adhesive knobs led to isolation of six trace amounts of metabolites, including two new metabolites, paganins A and B (1 and 2), blumenol A (3), talathermophilins A and B (4 and 5), and cyclo(glycyltryptophyl) (6). Compounds 3-6 were reported for the first time from carnivorous fungi. Compounds 1 and 2 promoted the formation of the predatory adhesive knobs with an increasing rate up to 118% at a concentration of 50 μM but showed moderate inhibitory activity at a concentration of 5 μM. Moreover, compounds 1 and 2 displayed strong inhibitory activities toward the formation of A. entomopaga conidiophores with inhibitory rates of 40-75%. Growth experiments suggested that compounds 1 and 2 could be involved in the regulation of the fungal predatory and reproductive abilities. Nematode chemotaxis bioassay indicated that compounds 1 and 3 displayed strong nematode-attracting abilities. These findings provided a new type of regulatory metabolite and support for the hypothesis that predators often evolve to respond to their metazoan prey.

First report of an unrecorded nematode-trapping fungus species Dactylellina candidum in Korea

Dactylellina candidum, a fungus that captures nematodes by means of non-constricting rings and stalked adhesive knobs, was isolated from rotten wood in the Euiseong area, South Korea. This fungus produces 1–3 fusiform or clavi-fusiform conidia, which are 2–4-septate (mainly 4-septate) and sized 36.0–45.4 × 7.3–9.7 µm (L × W), at the conidiophore apex. This is the first report of Dactylellina candidum in Korea. This fungus should be considered a potential biological control agent for plant-parasitic nematodes. Key words: Dactylellina candidum, nematode-trapping fungus, non-constricting rings, stalked adhesive knob, unrecorded species.

First Report of an Unrecorded Nematode-Trapping Fungus Species Monacrosporium phymatopagum in Korea

A fungus that can capture nematodes by means of sessile adhesive knobs was isolated from rotten wood in Uiseong, Korea. It was found to produce single, spindle-shaped, 3-4 septate (commonly 4-septate) conidia, (range, ) long and (range, ) wide. Conidiophores were found to be hyaline, erect, straight, and high. On the basis of these morphological features, the fungus was identified as Monacrosporium phymatopagum. This is the first report of M. phymatopagum in Korea which can be a potential biological control resource of plant parasitic nematode.

Predation of Ancylostoma spp. dog infective larvae by nematophagous fungi in different conidial concentrations

In the present work, it was evaluated the in vitro effect of 12 isolates from the fungal species Arthrobotrys, Duddingtonia, Nematoctonus and Monacrosporium genera in different conidial concentrations on the capture of Ancylostoma spp. dog infective larvae (L 3), on 2% water-agar medium at 25 °C, at the end of a period of 7 days. The concentrations used for each nematophagous fungus were 1000, 5000, 10,000, 15,000 and 20,000 conidia/Petri dish plated with 1000 Ancylostoma spp. L 3. All nematode-trapping fungi isolates tested reduced the averages of the uncaptured Ancylostoma spp. L 3 recovered, with the increase of the fungal inoculum concentration, in comparison to the fungus-free control ( p < 0.05). The adhesive network producing species were better predators than the constricting ring or adhesive knob producing species. Duddingtonia flagrans (Isolate CG768) was the most effective, reducing the averages of the uncaptured Ancylostoma spp. L 3 recovered in 92.8%, 96.3%, 97.5%, 98.3% and 98.9%, respectively in five fungal inoculum concentrations established. Other effective nematophagous fungi were Arthrobotrys robusta (Isolate I31), which reduced the averages of the uncaptured Ancylostoma spp. L 3 recovered in 85.4%, 88.3%, 90.7%, 92.5% and 95.2%, and Arthrobotrys oligospora (Isolate A183), with reductions of 66.6%, 79.8%, 86.8%, 89.5% and 90.8%, respectively for both, in the five fungal inoculum concentrations established. No difference was found between Isolates A183 and I31 in the conidial concentrations of 15,000/Petri dish. Nematoctonus robustus (Isolate D1) and Arthrobotrys bronchophaga (Isolate AB) had the smallest percentages of reduction among the tested isolates and showed the lowest predacious activity. The Isolates CG768, I31 and A183 were considered potential biological control agents of Ancylostoma spp. dog free-living stages, being directly influenced by the fungal inoculum concentration.

Costa Rican species ofNematoctonus(anamorphic Pleurotaceae)

Nematoctonus (Hyphomycetes) and Hohenbuehelia (Agaricales, Pleurotaceae) are the names for the asexual and sexual stages of a genus of nematode-destroying fungi (Basidiomycota). Six morphospecies of Nematoctonus, all previously described, were isolated from fruiting bodies of Hohenbuehelia and from 439 samples of soil and organic debris collected in all 12 Holdridge life zones in Costa Rica. Nematoctonus was recorded in all but three life zones at the lowest and highest altitudes: tropical dry forest, tropical moist forest, and subalpine rain paramó. Isolates of Nematoctonus were identified by the micromorphology of their conidia and adhesive knobs, which are usually an hourglass-shaped secretory cell surrounded by a drop of mucilage. Adhesive knobs were found either exclusively on hyphae in predatory species ( Nematoctonus robustus F.R. Jones), exclusively on germinated conidia in parasitoid species ( Nematoctonus leptosporus Drechsler, Nematoctonus pachysporus Drechsler, and Nematoctonus tylosporus Drechsler) or on both hyphae and germinated conidia in a group we term “intermediate predators” ( Nematoctonus angustatus Thorn &amp; G.L. Barron, Nematoctonus geogenius Thorn &amp; G.L. Barron, and one monokaryotic isolate of N. robustus). Teleomorph–anamorph connections, made by culturing the anamorph from a teleomorph fruiting body, were made for N. angustatus (Hohenbuehelia angustata (Berk.) Singer), N. geogenius (Hohenbuehelia petalodes (Fr.) Schulz.), N. leptosporus (an unidentified Hohenbuehelia), and N. robustus ( Hohenbuehelia grisea (Peck) Singer).

Phylogenetic analyses of Nematoctonus and Hohenbuehelia (Pleurotaceae)

Hohenbuehelia (Agaricales, Pleurotaceae) and Nematoctonus (Hyphomycetes) are the names for the sexual and asexual stages of a genus of nematode-destroying fungi (Basidiomycota). We obtained partial sequences of nuclear ribosomal DNA, including the internal transcribed spacer region and the 5′ end of the large subunit, of 37 isolates of Hohenbuehelia and Nematoctonus representing 13 of the 16 described species in Nematoctonus. Phylogenetic analyses support Hohenbuehelia–Nematoctonus as a monophyletic clade of the Pleurotaceae, within which the species were placed in five main subclades. Exclusively predatory species ( Nematoctonus brevisporus Thorn &amp; G.L. Barron, Nematoctonus campylosporus Drechsler, Nematoctonus robustus F.R. Jones, and Nematoctonus sp. UAMH 5317) appear to be basal. In these species, adhesive knobs to capture prey are produced on their hyphae but not on their conidia. A single mycelial individual may feed on many nematodes. From these have arisen both exclusively parasitoid species ( Nematoctonus cylindrosporus Thorn &amp; G.L. Barron, Nematoctonus leiosporus Drechsler, Nematoctonus leptosporus Drechsler, Nematoctonus pachysporus Drechsler, Nematoctonus tylosporus Drechsler), and species that we call intermediate predators ( Nematoctonus angustatus Thorn &amp; G.L. Barron, Nematoctonus concurrens Drechsler, Nematoctonus geogenius Thorn &amp; GL. Barron, Nematoctonus hamatus Thorn &amp; G.L. Barron, and Nematoctonus subreniformis Thorn &amp; G.L. Barron). Exclusively parasitoid species have conidia that germinate to form sticky knobs that attach to passing nematodes but lack adhesive knobs on the hyphae. Each mycelial individual feeds on only one nematode. Intermediate predators have adhesive knobs both on hyphae and on germinated conidia and can act in both predatory and parasitoid modes. Most morphospecies are resolved as monophyletic, but sequences of additional gene regions are required to clarify species limits within the N. angustatus – N. geogenius group.

Evolution of nematode-trapping cells of predatory fungi of the Orbiliaceae based on evidence from rRNA-encoding DNA and multiprotein sequences.

Among fungi, the basic life strategies are saprophytism, parasitism, and predation. Fungi in Orbiliaceae (Ascomycota) prey on animals by means of specialized trapping structures. Five types of trapping devices are recognized, but their evolutionary origins and divergence are not well understood. Based on comprehensive phylogenetic analysis of nucleotide sequences of three protein-coding genes (RNA polymerase II subunit gene, rpb2; elongation factor 1-alpha gene, ef1-alpha; and ss tubulin gene, bt) and ribosomal DNA in the internal transcribed spacer region, we have demonstrated that the initial trapping structure evolved along two lineages yielding two distinct trapping mechanisms: one developed into constricting rings and the other developed into adhesive traps. Among adhesive trapping devices, the adhesive network separated from the others early and evolved at a steady and gentle speed. The adhesive knob evolved through stalk elongation, with a final development of nonconstricting rings. Our data suggest that the derived adhesive traps are at a highly differentiated stage. The development of trapping devices is felicitous proof of adaptive evolution.

Two new species of nematode-trapping fungi: relationships inferred from morphology, rDNA and protein gene sequence analyses

Two new nematode-trapping fungi, Dactylellina sichuanensis and D. varietas from China, which capture nematodes by both adhesive knobs and non-constricting rings, are described and illustrated. D. sichuanensis is characterized by both adhesive knobs and non-constricting rings, solitary conidiophores and 3-(4)-6 septate conidia, as compared with species such as D. appendiculata, D. candida, D. leptospora and D. lysipaga. Although D. sichuanensis shares similar types of trapping devices, the presence of simple conidiophores and spindle-shaped conidia with these species, it can be distinguished by its larger conidia and presence of more than four septa. In D. sichuanensis, a single conidium is born at the tip of conidiophore, while in D. candida, 3–10 conidia are born near the apex of conidiophore in a capitate arrangement. It produces spindle-shaped conidia with 3–6 septa, whereas D. leptospora produces cylindrical-shaped conidia with 5–15 septa. D. appendiculata captures nematodes by adhesive knobs whereas D. sichuanensis captures nematodes by both adhesive knobs and non-constricting rings. They also differ in conidial size (35–82.5 μm in D. sichuanensis as compared with 57–108 μm in D. appendiculata). D. varietas is characterized by conidiophores that are branched at right-angles, and elongate to fusoid conidia, with 7–8 septa (more than 25% of which are curved). D. varietas resembles D. asthenopaga, Dactylella oxyspora and Monacrosporium multiseptatum, but has elongate-fusoid conidia, whereas D. asthenopaga possesses obconical or clavate conidia. D. varietas forms both adhesive knobs and non-constricting rings whereas Dactylella oxyspora does not produce any trapping device. M. multiseptatum differs from D. varietas in having larger conidia with an inflated middle cell. Phylogenetic analyses based on nuclear and protein coding DNA sequences (18 S, and a combined 28 S + 5.8 S + β-tubulin dataset) indicate that these two taxa should be assigned to the family Orbiliaceae.

Phylogenetics and evolution of nematode-trapping fungi (Orbiliales) estimated from nuclear and protein coding genes

The systematic classification of nematode-trapping fungi is redefined based on phylogenies inferred from sequence analyses of 28S rDNA, 5.8S rDNA and beta-tubulin genes. Molecular data were analyzed with maximum parsimony, maximum likelihood and Bayesian analysis. An emended generic concept of nematode-trapping fungi is provided. Arthrobotrys is characterized by adhesive networks, Dactylellina by adhesive knobs, and Drechslerella by constricting-rings. Phylogenetic placement of taxa characterized by stalked adhesive knobs and non-constricting rings also is confirmed in Dactylellina. Species that produce unstalked adhesive knobs that grow out to form loops are transferred from Gamsylella to Dactylellina, and those that produce unstalked adhesive knobs that grow out to form networks are transferred from Gamsylella to Arthrobotrys. Gamsylella as currently circumscribed cannot be treated as a valid genus. A hypothesis for the evolution of trapping-devices is presented based on multiple gene data and morphological studies. Predatory and nonpredatory fungi appear to have been derived from nonpredatory members of Orbilia. The adhesive knob is considered to be the ancestral type of trapping device from which constricting rings and networks were derived via two pathways. In the first pathway adhesive knobs retained their adhesive material forming simple two-dimension networks, eventually forming complex three-dimension networks. In the second pathway adhesive knobs lost their adhesive materials, with their ends meeting to form nonconstricting rings and they in turn formed constricting rings with three inflated-cells.

Phylogenetics and evolution of nematode-trapping fungi (Orbiliales) estimated from nuclear and protein coding genes

The systematic classification of nematode-trapping fungi is redefined based on phylogenies inferred from sequence analyses of 28S rDNA, 5.8S rDNA and β-tubulin genes. Molecular data were analyzed with maximum parsimony, maximum likelihood and Bayesian analysis. An emended generic concept of nematode-trapping fungi is provided. Arthrobotrys is characterized by adhesive networks, Dactylellina by adhesive knobs, and Drechslerella by constricting-rings. Phylogenetic placement of taxa characterized by stalked adhesive knobs and non-constricting rings also is confirmed in Dactylellina. Species that produce unstalked adhesive knobs that grow out to form loops are transferred from Gamsylella to Dactylellina, and those that produce unstalked adhesive knobs that grow out to form networks are transferred from Gamsylella to Arthrobotrys. Gamsylella as currently circumscribed cannot be treated as a valid genus. A hypothesis for the evolution of trapping-devices is presented based on multiple gene data and morphological studies. Predatory and nonpredatory fungi appear to have been derived from nonpredatory members of Orbilia. The adhesive knob is considered to be the ancestral type of trapping device from which constricting rings and networks were derived via two pathways. In the first pathway adhesive knobs retained their adhesive material forming simple two-dimension networks, eventually forming complex three-dimension networks. In the second pathway adhesive knobs lost their adhesive materials, with their ends meeting to form nonconstricting rings and they in turn formed constricting rings with three inflated-cells.