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FEBS Letters 580 (2006) 2–8 The biological clock of an hematophagous insect: Locomotor activity rhythms, circadian expression and downregulation after a blood meal Antonio C.A. Meireles-Filho, Gustavo B. da S. Rivas, Joa˜o S.M. Gesto, Ricardo C. Machado, Constanc¸a Britto, Nataly A. de Souza, Alexandre A. Peixoto* Department of Biochemistry and Molecular Biology, Instituto Oswaldo Cruz – Fiocruz, Av. Brasil 4365, Manguinhos, CEP 21045-900, Rio de Janeiro, Brazil Received 4 October 2005; revised 10 November 2005; accepted 13 November 2005 Available online 1 December 2005 Edited by Gianni Cesareni and PDP1e compete for the same site in the Clk promoter, reg- Abstract Despite the importance of circadian rhythms in vec- tor-borne disease transmission, very little is known about its ulating its transcription. molecular control in hematophagous insect vectors. In Drosoph- These two interlocked feedback loops create circadian ila melanogaster, a negative feedback loop of gene expression rhythms of gene expression of its components, except for has been shown to contribute to the clock mechanism. Here, cyc, which is constitutively expressed [1,5]. The repressor we describe some features of the circadian clock of the sandfly genes per and tim, for example, have their peaks of mRNA Lutzomyia longipalpis, a vector of visceral leishmaniasis. Com- expression around Zeitgeber Time (ZT)