Daily rhythms of PERIOD protein in the eyestalk of the American lobster, Homarus americanus

Abstract

The daily rhythm of PERIOD (PER) protein expression is an integral component of the circadian clock, which is found among a broad range of animal species including fruit flies, marine mollusks, and even humans. The use of antibodies directed against PER has provided a helpful tool in the discovery of PER homologs and the labeling of putative pacemaker cells, especially in animals for which an annotated genome is not readily available. In this study, Drosophila-PER antibodies were used to probe for PER in the American lobster, Homarus americanus. This species exhibits robust endogenous circadian rhythms but the circadian clock has yet to be located or characterized. PER was detected in the eyestalks of the lobster but not in the brain. Furthermore, a significant effect of the light/dark cycle on daily PER abundance was identified, and PER was significantly more abundant at mid-dark than in early light or mid-light hours. Our results suggest that PER is a part of the molecular machinery of the circadian clock located in the eyestalk of the lobster.

Keywords:

• lobster
• Homarus americanus
• biological clock
• circadian
• PERIOD protein
• PER
• daily
• rhythms
• eyestalk

Acknowledgments

The authors thank Luciana Ferraris for help with the Western blotting and Win Watson for many useful conversations on lobster behavior and physiology and to Susan Swope for help with Western blotting. The authors also thank the NSF (IOS-090342 to CCC and WHW III) and the New Hampshire IDeA Network of Biological Research Excellence with grants from the National Center for Research Resources (5P20RR030360-03) and the National Institute of General Medical Sciences (8P20GM103506-03), National Institutes of Health for support in writing the article.