GENETIC ANALYSIS OF LEARNING AND MEMORY IN C. elegans

• Published in: Genes & Genetic Systems Vol. 75; no. 6; p. 368
• Main Authors: MOHRI Akiko, KOIKE Mizuho, MORI Ikue
• Format: Journal Article
• Language: Japanese
• Published: The Genetics Society of Japan 2000
• ISSN: 1341-7568

Thermotaxis is an important behavior that C. elegans uses to ensure its survival and reproduction in the natural habitat. On a temperature gradient, C. elegans migrates toward its cultivation temperature after well-fed experience, whereas it migrates away from the cultivation temperature after starved experience (1). Here, we closely examined thermotaxis of wild type (N2) animals in order to investigate components required for the reversal of temperature preference. We found that C. elegans can associate cultivation temperature with feeding state information, and then modifies behavioral outputs in response to environmental changes. As already reported, exogenous serotonin can mimic well-fed state (2). We also obtained the evidence to suggest that serotonin can act as a food signal in thermotaxis. Negative thermotaxis turned into positive thermotaxis after cultivation at 25-degree on unseeded plate containing serotonin as well as on seeded plate. However, serotonin-related monoamine mutants showed almost normal responses in the reversal of thermotaxis behavior, except for cat-1 (e1111) mutant. Although these results seem to be inconsistent with the importance of serotonin release in well-fed state, these results suggest that serotonin is not a sole determinant of feeding signal. To identify genes and cells required for associating temperature memory with the feeding state, mutants were sought that can respond to feeding states normally, but are defective in the reversal of thermotaxis behavior. About 3,700 genomes were screened for animals that constitutively migrate to cultivation temperatures regardless of the starvation experience. Several mutant candidates, which exhibit the aimed behavioral abnormality, were obtained, and they were designated aho (abnormal hunger Orientation) mutants. We are grateful to G. Ruvkun, Y. Shibata and S. Takagi for serotonin-related mutants. (1)Hedgecock and Russell, 1975, PNAS 72, 4061-4065. (2)Horvitz et al., 1982, Science 216, 1-12-1014.