The intergenic spacer region of the rDNA in Olea europaea L.

Abstract

The intergenic spacer (IGS) region of rDNA in Olea europaea is 5,629 bp long and it can be subdivided, on the basis of the different features, into six regions; two of them, located upstream and downstream of the putative transcription initiation site (TIS), respectively, contain prominent and unrelated subrepeats (s.r.). The upstream s.r. are 75–86 bp in length and the downstream ones are about 160 bp in length. The first type is represented by a high number (36) of iterations, which share a mutual similarity of 82.5%. A single sequence (TATTATAGGGGGGAGG) is found, which fits the reported TIS of plants and the position +1 would correspond to the adenine at position 3,622 after the 3′ end of 25 S ribosomal RNA (rDNA) genes. Moreover, in Olea IGS region some unusual features are observed and discussed in relation to analogous data present in the literature.