Characterization of a new prominent satellite DNA of Cucumis metuliferus and differential distribution of satellite DNA in cultivated and wild species of Cucumis and in related genera of Cucurbitaceae

A new species-specific, tandemly arranged satellite (pMetSat) DNA was characterized by Southern hybridization, cloning and sequencing for Cucumis metuliferus, a cultivated species that originated in Africa. The 346 bp repeats share short stretches of remarkable sequence similarity with satellite DNA of other cultivated Cucumis species, in particular types I-IV of C. sativus (cucumber) and the 352 bp satellite of C. melo (melon), although no crosshybridization occurs applying stringent conditions. Minor arrays of the respective repeat types were also detected in other less cultivated or wild Cucumis species by PCR amplification or long exposure of Southern blots. For the Cucumis species, the pattern of satellite distribution appears to reflect the taxonomic classification. This suggests that in ancestral species a set of differential but related repeats was already present. During speciation and cultivation, specific members of this set underwent amplifications and modifications. Differential distribution of small arrays of the Cucumis satellites within the genomes of other Cucurbitaceae (tribus Benincaseae, Trichosantheae, Sicyeae) is shown.