Laboratory of Molecular Cytogenetics

We study the structure and function of nuclear genomes in insects and other arthropods with emphasis on key questions of chromosome biology and evolution. For chromosome research we use advanced methods of molecular cytogenetics along with standard cytogenetic techniques. The methods include various modification of fluorescence in situ hybridization (FISH) such as FISH with telomeric and rDNA probes, genomic in situ hybridization (GISH), comparative genomic hybridization (CGH), gene mapping with the help of bacterial artificial chromosome (BAC) probes (the so-called BAC-FISH), and comparative chromosome painting (Zoo-FISH) with chromosome-specific probes prepared by laser microdissection. We also construct and further use for research DNA sequence libraries of microdissected chromosomes.

Current research projects

Molecular differentiation and evolutionary history of sex chromosomes in Lepidoptera

Molecular evolution of sex chromosomes in Lepidoptera

Sex chromosomes and their differentiation belong to most interesting questions of evolutionary genetics. In animals, overwhelming majority of data on the sex chromosome evolution were obtained in organisms with male heterogamety (i.e. with XY sex chromosome systems) such as flies and mammals. Much less is known about organisms with female heterogamety, possessing a WZ sex chromosome system or its variations. This particularly regards moths and butterflies (Lepidoptera), the largest animal group with female heterogamety. In selected models we study physical features of lepidopteran genomes, perform synteny mapping of conserved genes, and examine molecular differentiation of sex chromosomes with the aim to uncover evolutionary history of lepidopteran karyotypes and contribute to understanding general mechanisms of sex chromosome evolution. This research is done in collaboration with Walther Traut (Lübeck, Germany) and Ken Sahara (Sapporo, Japan).

[PI: F. Marec]

Development of genetic sexing lines in the codling moth

Scheme of genetic sexing in Lepidoptera using transgenic females

The codling moth, Cydia pomonella, is the key pest of pome fruit and walnut orchards in the temperate regions of the world. The extensive use of insecticides used to control this pest has resulted in the development of resistance to these chemicals, and there is an increasing demand on the use of environment-friendly control tactics such the Sterile Insect Technique (SIT). Codling moth SIT relies on the mass rearing and release of genetically sterile both males and females into a wild population. Male-only releases could significantly reduce costs and increase efficiency of SIT. Our goal is to develop genetic sexing lines of the codling moth by inserting a selectable transgene (a dominant conditional lethal mutation of the Notch gene) into the female-specific W chromosome.  Under restrictive conditions the transgene would abort development of females and thus, non-transgenic male-only offspring would be produced for irradiation and release. Research steps to achieve this goal include identification of molecular markers of the sex chromosomes, isolation of codling moth ortholog of the Notch gene, creation of plasmid constructs carrying a temperature-sensitive mutant allele of the Notch gene, generation of transgenic lines, and mapping of the inserted transgene on the W chromosome. This research is part of international project co-ordinated by IAEA (Vienna, Austria) and is done in collaboration with Lisa G. Neven (Wapato, WA, USA).

[PI: F. Marec]

Molecular and cytogenetic analysis of Drosophila telomeres

Drosophila telomere. A. Telomere structure. B. Telomeric heterochromatin.

In most eukaryotes, telomeric DNA consists of a long array of short DNA repeats maintained at the ends of chromosomes by telomerase; a (TTAGG)n sequence was found in telomeres of many insects. In our previous research, we proved that the (TTAGG)n sequence is an ancestral motif of telomeres not only in insects but in all arthropods. However, the motif was lost in some taxons and replaced with another yet-unknown motif or with an alternative mechanism of telomere maintenance. For example,telomeres in Drosophila are composed of three telomeric retroelements ((HeT-A, TART, and TAHRE). Multiple repeats of these elements form a terminal region of the telomere, the so-called HTT array. Length of Drosophila telomeres is maintained by transposition of the telomeric retroelements targeted to the chromosome ends. The HTT arrays are adjacent to the heterochromatin telomere-associated sequence (TAS). Due to properties of the heterochromatin, the TAS has a silencing effect on gene expression in the HTT array participating, according to our results, in the control of telomere length. Presently, we study the Drosophila telomere length control in relation to the transcription of telomeric elements and telomeric chromatin structure.

[PI: R. Čapková Frydrychová]

Repetitive DNA in the genome of Lepidoptera

Genome sizes in moths and butterflies differ dramatically not only between distant species, but alsobetween close relatives. This feature is general in eukaryotic organisms and is caused by differentamounts of the so-called selfish (repetitive) DNA, i.e. satellites and mobile elements. In a short-term perspective, the selfish DNAs are considered to be genomic parasites, with either neutral or negative impact the host (e.g. waste of cell energy), changes in gene expression); however, they can be advantage in a long-term perspective (e.g. some satellite DNAs are necessary for proper function of some chromosome structuressuch as telomeres). Moreover, repetitive DNAs have been repeatedly shown to play an important role in the evolution of their hosts (e.g. duplication/deletion of genomic regions, origin of new genes).In our laboratory, we study structure and composition of repetitive DNAs in selected species of Lepidoptera, namely in the codling moth (Cydia pomonella) and the Indianmeal moth (Plodia interpunctella). To be more specific, we are concerned with the identification and localization of new satellite DNAs and new mobile elements and also with their chromosomal mapping. In the Indianmeal moth and its relative, the Mediterranean flour moth (Ephestia kuehniella), we focus mainly on the W sex chromosome, which considerably differs from the other genomic regions due to the absence of recombination and which is rich in repetitive DNAs.

[PI: M. Vítková]

CONTACT

Biology Centre CAS
Institute of Entomology
Branišovská 1160/31
370 05 České Budějovice

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