Circadian rhythms in C. elegans: locomotor activity, stress tolerance and metabolism

SERGIO H. SIMONETTA; ANDRÉS ROMANOWSKI; M. LAURA MIGLIORI; DIEGO GOLOMBEK

Florida. USA

Congreso; Research on Biological Rhythms: 11th Biennial Meeting; 2008

Circadian rhythms in C. elegans: locomotor activity, stress tolerance and metabolism Sergio H. Simonetta1, Andrés Romanowski1, M. Laura Migliori1 and Diego Golombek11 Laboratorio de Cronobiología, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal, Buenos Aires, Argentina C. elegans is a model organism widely used in various areas of research but not well characterized in chronobiological studies. We have recently designed an automated device to track individual nematodes and demonstrated the existence of circadian activity rhythms in both LD (light : dark, 12 h : 12 h) and DD (constant darkness) conditions, periods were found to be of 24.2±0.44 h and 23.1±0.40 h respectively. In order to determine if the worms are able to see green wavelength, now we are studying the phototaxic response using green light filters (520nm). Phototaxis data showed a phototaxis index of 0,698 ± 0,096 towards the green wavelength of light. Another approach to uncover rhythmic outputs was the study of stress tolerance behaviors. We found that C. elegans showed rhythmic stress tolerance patterns for oxidative and osmotic stress with peaks at ZT 12 (lights on) and ZT 0 (lights off), respectively.  Stress related genes’ expresssion was determined by sqRT-PCR: gpdh-1 and gpx showed a significant diurnal variation.We have also studied circadian rhythms in metabolic variables, such food consumption and defecation.  Food consumption rate (determined by decreasing OD600 of OP50 E. coli) was shown to be rhythmic and a peak was found in the evening (ANOVA, p<0.0001). Defecation rhythms also showed to governed in a circadian manner. These results show that control animals have a 24 h period in the frequency of the ultradian defecation rythm (ANOVA, p< 0,0001). Furthermore, the defecation behaviour of the JT73 mutant strain depicts a normal rythmic pattern on a circadian level (ANOVA, p < 0,01).Finally, we have measured aaNAT actiivity and melatonin levels, also as a possible circadian output signal in C. elegans. Our results show that aaNAT activity peaks at ZT 12. In summary, our results show that several different circadian outputs can be recorded in C. elegans, and the circadian rhythm of locomotor activity cn be entrained to environmental signals. These data might be a basis for the screening of outative circadian mutants in this species.