engleski

How satellite DNAs in the “library” are created?

A pool of satellite DNAs amplified in differing abundances in a taxonomic group is referred to as a satellite DNA library. Major satellite DNAs in two closely related nematodes, Meloidogyne chitwoodi and M. fallax have been characterized previously (1, 2). We studied evolution and organization of these sequences in the genomes of the two species. Results reveal a pool of satellite DNAs common to both of them, in accordance to the “library” model. To understand genesis of the library we cloned and analysed in details long satellite arrays from both species. Long tracts are composed of monomers of different satellite DNAs, organized in tandem together with inserted segments of unrelated sequence, showing complex organization in the form of higher order repeats (HORs). These HORs could be the origin of expanded tandem arrays in the “library” and/or the place of creation of novel satellite repeats based on extensive rearrangements between different satellite monomers. In addition, search in Expressed Sequence Tags (ESTs) database from parasitic nematodes revealed significant similarity of the analysed HOR sequence with mRNA of unknown function from a cDNA library of M. chitwoodi. These results suggest the transcriptional activity of the HOR in both M. chitwoodi and M. fallax species, which may be the basis of HOR persistence in both genomes.

genome; repetitive sequences; satellite DNA library

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