Predation is one of the universal features of the natural world which help shape the evolution and diversity of species throughout the tree of life. Since every organism within the animal kingdom acts as either a consumer or the consumed, predation plays an important role in maintaining the balance of the ecosystem.
Some species of plants have evolved to capture and consume small animals to allow them to survive nutrient-poor environments. Similarly, there are also members of the fungal kingdom which have evolved strategies for killing and consuming nematodes.
Intriguing Carnivorous Fungus
A seemingly innocent fungus called Arthrobotrys oligospora has caught the attention of biologists due to its apparently split personality. Behind its fascinating characteristics is its tendency to be systematic predators or worms.
In a new study, scientists have shed light on the molecular processes involved in the killing mechanisms of the carnivorous fungus species. Led by Hung-Che Lin of Academia Sinica in Taipei, Taiwan, the research team investigated how Arthrobotrys oligospora traps and consumes a worm.
Previous study has revealed some of the secrets behind this predatory relationship, particularly the certain genes involved in A. oligospora's trap formation. However, the molecular details of these processes are still shrouded in mystery.
To deepen their understanding on this matter, Lin and colleagues conducted a series of laboratory experiments where they investigated the various stages of A. oligospora predation. They focused on the genes and processes involved in consuming a species of worm called Caenorhabditis elegans.
The team used a technique called RNAseq, which provided information on the level of activity of various A. oligospora genes at different points in time. The research findings have revealed many biological processes which play key roles in A. oligospora predation.
In the study entitled "Key processes required for the different stages of fungal carnivory by a nematode-trapping fungus", the researchers suggest that when the fungus first senses a worm, it shows an increase in DNA replication and ribosome production. Then, the activity increases many proteins that encode proteins which assist in the formation and function of traps. Finally, A. oligospora extends filamentous structures called hyphae into a worm to digest it, an activity boosted by gene coding for proteases.
The researchers believe that their comprehensive transcriptomics and functional analyses highlight the role of increased DNA secretion, translation, and replication in trap development and efficacy. Additionally, a gene family expanded in the genomes of nematode-trapping fungi was discovered to be enriched in traps for hunting nematodes.
Understanding Fungal Evolution
Arthrobotrys oligospora usually derives its nutrients from decaying organic matter. However, starvation and the presence of nearby worms can prompt this fungus to form traps to capture and consume nematodes. This worm-hunting fungus is just one of many fungal species with the ability to trap and eat very small animals.
Carnivorous can be found in divergent lineages, an indication that predation in fungi has evolved independently multiple times during their evolution. The findings of the study have confirmed the evolutionary expansion of fungal genes which is potentially linked to the predatory lifestyle of A.oligospora. The researchers conclude that the evolution and expansion of predatory fungus in specific lineages resulted from dramatic size differences between family members. It is also attributed to pressures in adapting to a wide diversity of nematode species.
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