The molecular and neural regulation of ultraviolet light phototaxis and its food-associated learning behavioral plasticity in C. elegans

Stress tolerance in entomopathogenic nematodes: Engineering superior nematodes for precision agriculture

Entomopathogenic nematodes (EPNs) are soil-dwelling parasitic roundworms commonly used as biocontrol agents of insect pests in agriculture. EPN dauer juveniles locate and infect a host in which they will grow and multiply until resource depletion. During their free-living stage, EPNs face a series of internal and environmental stresses. Their ability to overcome these challenges is crucial to determine their infection success and survival. In this review, we provide a comprehensive overview of EPN response to stresses associated with starvation, low/elevated temperatures, desiccation, osmotic stress, hypoxia, and ultra-violet light. We further report EPN defense strategies to cope with biotic stressors such as viruses, bacteria, fungi, and predatory insects. By comparing the genetic and biochemical basis of these strategies to the nematode model Caenorhabditis elegans, we provide new avenues and targets to select and engineer precision nematodes adapted to specific field conditions.

Association of Two Opposing Responses Results in the Emergence of a Novel Conditioned Response

Recent studies examining association of opposing responses, contrasting emotional valences, or counter motivational states have begun to elucidate how learning and memory processes can translate to clinical therapies for trauma or addiction. In the current study, association of opposing responses is tested in C. elegans. Due to its relatively simple and well-described nervous system, it was hypothesized that association of two oppositional stimuli presented in a delayed conditioning protocol would strengthen the behavioral response to the first stimulus (alpha conditioning). To test this, C. elegans were exposed to a tone vibration stimulus (to activate a mechanosensory-driven locomotor reversal response) paired with a blue light (to activate a forward locomotor response) at a 2-s delay. After five pairings, behavior was measured following a tone-alone stimulus. Worms that received stimulus pairing did not show an enhanced response to the first presented stimulus (tone vibration) but rather showed a marked increase in time spent in pause (cessation of movement), a new behavioral response (beta conditioning). This increase in pause behavior was accompanied by changes in measures of both backward and forward locomotion. Understanding the dynamics of conditioned behavior resulting from pairing of oppositional responses could provide further insight into how learning processes occur and may be applied.