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High conservation of the differentially amplified MPA2 satellite DNA family in parthenogenetic root-knot nematodes

Sequence variability and distribution of a newly characterized MPA2 satellite DNA family are described in five root-knot nematode species of the genus Meloidogyne, the mitotic parthenogens M. paranaensis, M. incognita, M. arenaria and M. javanica, and the meiotic/mitotic M. hapla (isolates A and B, respectively). The lack of distinctive mutations and the considerable contribution (40.8%) of ancestral changes disclose an ancient satellite DNAwhich existed in the common ancestor of extant parthenogenetic species in the same or similar form and remained preserved for a period of at least 43 My. Nonuniformly distributed polymorphic sites along the satellite monomer suggest differences in constraints acting on particular sequence segments. Sequence diversity is clearly unaffected by significant differences in genomic abundance of the MPA2 satellite DNA in the examined species. Observed results suggest that the dynamics of this satellite DNA family might be in the first instance a consequence of characteristics of its nucleotide sequence and possible constraints imposed on it. Under conditions of mitotic and meiotic parthenogenesis, slow accumulation of mutations and slow replacement of old MPA2 sequence variants with new ones may be equivalent to the dynamics of some satellite DNA sequences conserved for extremely long evolutionary periods in sexual species.

sequence variability; ancestral mutations; satellite DNA evolution; copy number; Meloidogyne

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