Crustacean s-PDH I but not s-PDH II rescues circadian rhythmicity in PDF-deficient

BECKWITH, EJ; DE LA IGLESIA, HO; CERIANI, MF

Huerta Grande, Córdoba

Congreso; II Reunión Conjunta de Neurociencias; 2010

Sociedad Argentina de Neurociencias

Internal circadian clocks control rhythms in physiology and behavior as an adaptation to the external day¡Vnight cycle. This daily clocks are present in virtually all living systems. Furthermore, plants and animal that live in the intertidial zone live not only in altering day and night, and are also subjected to cycling exposure to air and inundation. Indeed, biological clocks that oscillate in synchrony with the tide, namely circatidial clocks, have been describe in several species Drosophila melanogaster has served as a model organism for the study of circadian rhythms mainly due to the availability of molecular genetic tools and the robustness of the locomotor behavioral profile. Among the peacemaking neurons in the fly brain, a group of eight ventral lateral neurons (LNvs) in each brain hemisphere express the neuropeptide pigment dispersing factor (PDF). This group could be subdivided in two subgroups, the large LNvs (lLNvs) and small (sLNvs). This last group is essentially important as circadian peacemakers for locomotor rhythms in constant darkness.Given the major adaptative value of biological clocks, the presence of tow clocks, circadian and circatidial, raise an evolutionary question: Could circatidial biological timing systems have evolved from preexisting ubiquitous circadian systems? Searching for putative common components of biological clocks we have cloned two ƒÒ-pigment-dispersing hormone (ƒÒ-PDH) isoforms from the intertidal crab Cancer productus. The distribution of ƒÒ-PDH I indicates that this peptide most likely acts as a neuromodulator, whereas ƒÒ-PDH II is the neurohorme present in the sinus gland. To test the circadian relevance of the ƒÒ-PDH isoforms we transformed Drosophila pdf null mutants and performed rescue experiments by overexpressing the neuropeptides in the PDF circuit. The results clearly show that ƒÒ-PDH I is able to replace PDF, while ƒÒ-PDH II could just accomplish a modest rescue of same behavioral characteristics of the pdf01 mutant.