EnglishCancella i cookie per ripristinare le impostazioni di lingua associate al browser in uso
Titolo/Abstract/Parole chiave

EVOLUTION OF THE CIRCADIAN CLOCK IN EXTREME ENVIRONMENT: LESSONS FROM CAVEFISH.

Cavallari, Nicola (2010) EVOLUTION OF THE CIRCADIAN CLOCK IN EXTREME ENVIRONMENT: LESSONS FROM CAVEFISH. Tesi di Dottorato , Università degli Studi di Ferrara.

[img]
Anteprima
File PDF
EVOLUTION_OF_THE_CIRCADIAN_CLOCK_IN_EXTREME_ENVIRONMENT.pdf

Download (17MB) | Anteprima

    Abstract

    Evolution has been strongly influenced by the daily cycles of temperature and light imposed by the rotation of the Earth. Fascinating demonstrations of this are seen in extreme environments such as caves where some animals have remained completely isolated from the day-night cycle for millions of years. Most of these species show convergent evolution, sharing a range of striking physical properties such as eye loss. One fundamental issue is whether “hypogean” species retain a functional circadian clock. This highly conserved, physiological timing mechanism allows organisms to anticipate daily environmental changes and is synchronized primarily by light. The Somalian cavefish, Phreatichthys andruzzii does possess a circadian clock that is entrained by a daily regular feeding time but strikingly, not by light. Under constant conditions the P. andruzzii clock oscillates with an extremely long period and also lacks normal temperature compensation. We document multiple mutations affecting a light-induced clock gene, Period2 as well as the genes encoding the extra-retinal photoreceptors Melanopsin (Opn4m2) and TMT-opsin. Remarkably, we show that ectopic expression of zebrafish homologs of these opsins rescues light induced clock gene expression in P. andruzzii cells. Thus, by studying this natural mutant we provide direct evidence for a peripheral light-sensing function of extra-retinal opsins in vertebrates. Furthermore, the properties of this cavefish illustrate that evolution in constant darkness leads not only to anatomical changes but also to loss of gene function linked with the detection and anticipation of the day-night cycle.

    Tipologia del documento:Tesi di Dottorato (Tesi di Dottorato)
    Data:26 Marzo 2010
    Relatore:Bertolucci, Cristiano
    Coordinatore ciclo:Barbujani, Guido
    Istituzione:Università degli Studi di Ferrara
    Dottorato:XXII Anno 2007 > BIOLOGIA EVOLUZIONISTICA E AMBIENTALE
    Struttura:Dipartimento > Biologia ed evoluzione
    Soggetti:Area 05 - Scienze biologiche > BIO/05 Zoologia
    Parole chiave:orologio circadiano, pesci ipogei, fotorecezione, geni orologio, compensazione della temperatura, opsine, circadian clock, cavefish, zebrafish, light pathway, clock mechanism, temperature compensation, opsins
    Depositato il:26 Lug 2010 08:20

    Staff:

    Accesso riservatoAccesso riservato