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

Abstract

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-␣ gene, ef1-␣; 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.

Underground leaves ofPhilcoxiatrap and digest nematodes

“…Moreover, we document a case of a plant that traps and digests nematodes with adhesive leaves. Nematode digestion has been extensively described in fungi (23,24) but is rare in plants. The discovery of carnivory in Philcoxia and its unique trapping method highlight the diversity of nutrient-acquisition mechanisms among plants in severely nutrient-impoverished environments, as shown in similar systems elsewhere in the world (25).…”

How carnivorous fungi use three-celled constricting rings to trap nematodes

“…Based on two fossil records and molecular clock calibration, fungal carnivorism diverged from saprophytism about 248.1 million years ago (Mya), shortly after the occurrence of the Permian-Triassic extinction event about 251.4 Mya. Active carnivorism (fungi with constricting rings) and passive carnivorism (fungi with adhesive traps) are distinct trapping mechanisms (Yang et al, 2007) that diverged from each other about 197.3 Mya, shortly after the occurrence of the Triassic-Jurassic extinction event about 201.4 Mya. The temporal correlation of the origin and evolution of fungal carnivorism in Ascomycota with major extinction events suggests that the presumably carbon-rich, nitrogen-poor environments created by mass extinctions might have been selected for fungi with the ability to capture and consume microscopic animals (unpublished data)…”

Búsqueda y aislamiento de hongos nematófagos vs Meloidogyne spp. en el norte de Sinaloa, México

“…Son considerados un grupo importante de microorganismos del suelo que pueden suprimir las poblaciones de nematodos parásitos de las plantas y animales. Se clasifican cuatro grupos de manera general en base a los mecanismos de ataque a los nematodos a) trampeo de nematodos: estos utilizan mecánicamente nódulos o hifas adhesivas, pertenecen a un grupo de ascomicetos asexuales con especies definidas por su tipo de dispositivos de captura (Scholler et al, 1999;Li et al, 2005;Yang y Liu, 2006;Yang et al, 2007); b) hongos endoparásitos usando sus esporas; c) los hongos que utilizan las puntas de sus hifas para invadir hembras y huevecillos; y d) hongos productores de toxinas que inmovilizan a los nematodos (Kendrick, 2001;Liu et al, 2009). …”

“…This are considered an important group of soil microorganisms that can suppress parasitic nematode populations of plants and animals. Four groups were classified overall based on the mechanisms of attack to nematodes a) trapping nematodes: these use mechanically nodules or adhesive hyphae, belong to a group of asexual ascomycete with defined species by its type of capture devices (Scholler et al, 1999;Li et al, 2005;Yang and Liu, 2006;Yang et al, 2007); b) endoparasitic fungi using its spores; c) fungi that use the tips of their hyphae to invade females and eggs; and d) fungi producing toxins that immobilizes nematodes (Kendrick, 2001;Liu et al, 2009). …”