engleski

Satellite DNAs library in the process of forming: the nematode view

The noncoding DNA sequences repeated in tandem, satellite DNAs (satDNAs) compose significant portion of every eukaryotic genome. Despite tremendous advances in sequencing and assembly of genomic DNA, satellite repeats are underrepresented in outputs of genome projects, which are still focused on non-repetitive, gene- rich euchromatic segments. However, more and more attention is given to the noncoding genomic fraction, because it gives an organizational framework to every eukaryotic genome, underlies pivotal genomic functions and may represent a major trigger in speciation. Unlike the coding part, satDNAs vary greatly in size and sequences even in closely related species and this extreme diversity raised difficulties in deriving general conclusions about the origin, evolution and function of satDNAs in higher organisms. The overview of our present studies on a group of root-knot nematodes (RKN) of genus Meloidogyne species will be presented. Moderate abundance and complex organization of different satellite repeats, defined phylogenetic relationships and available source of genome sequencing data make root-knot-nematode species an attractive model system to study satellite DNAs. Our studies focused on satDNAs evolution in Meloidogyne genomes will be delineated (i) results relate stochastic processes and selective pressure in the evolution of satellite DNAs, (ii) explaination of the origins of different forms of satellite DNAs coexisting in genomes in the form of a common library and (iii) role of recombination mechanisms in structuring complex satellite repeats. Although concluded on a limited sample of RKN species, we suggest that obtained information describes general behavior characteristics of satellite DNAs in eukaryotic genomes.

non-coding DNA; evolution; nematodes

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