Circadian biological clocks are found in most living organisms and their fundamental properties are highly conserved in vertebrates and invertebrates. The fruitfly, Drosophila melanogaster served as a premier insect species for the molecular analysis of the circadian rhythms. Because of the functional similarities of the circadian clocks among all metazoans, it was suggested that the molecular mechanisms underlying the clock function would be conserved as well. Surprisingly, we have found striking differences between the molecular regulations of the circadian timing system even among holometabolous insects. The long-term goal of our laboratory is to gain a better understanding of the cellular and molecular mechanisms that underlie circadian rhythmicity.
Although seasonal clocks are widespread in animals, their molecular mechanism is not understood. The key reason for this is the absence of solid photoperiodic phenotype in typical genetic model organisms. Therefore, we have found suitable model with robust photoperiodic and circadian phenotypes and recently we are introducing genetics and functional tools into this organism, Pyrrhocoris apterus.
[P.I. David Dolezel]
Dolezel D., Zdechovanova L., Sauman I., Hodkova M. (2008) Endocrine-dependent expression of circadian clock genes in insects. Cell. Mol. Life Sci. 65: 964-969. (pdf)
Košťál V., Tollarová M., Doležel D. (2008) Dynamism in physiology and gene transcription during reproductive diapause in a heteropteran bug, Pyrrhocoris apterus. J. Insect Physiol. 54: 77-88.
Dolezel D., Sauman I., Kostal V., Hodkova M. (2007) Photoperiodic and food signals control expression pattern of the clock gene, period, in the linden bug, Pyrrhocoris apterus. J. Biol. Rhythms 22: 335-342. (pdf)
The circadian transcription of the tim gene is tightly regulated by the protein complex dCLK/CYC, which directly interacts with a series of closely spaced E-box and E-box-like elements in the Drosophila timeless promoter. The tim promoter from D. melanogaster has been studied in detail both in tissue cultures and in living flies, yet has never been investigated in other species.
Therefore we performed a detailed functional analysis of the tim promoter from the drosophilid fly, Chymomyza costata in Drosophila tissue cultures. A comparison of tim promoters from wt and npd-mutants confirmed that the 1855 bp deletion in the latter removes crucial regulatory cis-elements as well as the minimal promoter, being subsequently responsible for the lack of tim mRNA expression.
[P.I. David Dolezel]
Alena Kobelková, Adam Bajgar, David Dolezel (in press) Functional molecular analysis of a circadian clock gene timeless promoter from the drosophilid fly Chymomyza costata J. Biol. Rhythms