5S ribosomal DNA of peach blossom Thyatira batis L.

Abstract

Genomic regions encoding 5S ribosomal RNA represent a convenient source of molecular markers. These genomic regions are composed of tandemly organized repeated units. Each unit consists of a highly conserved 5S rRNA coding region and a variable intergenic spacer (IGS). Within the IGS, regulatory elements involved in 5S rDNA transcription are located. Given that 5S rDNA is present in the genomes of all eukaryotes, this region can be used as a universal model to study molecular evolution in different taxa. Molecular studies of Lepidoptera have always been of considerable practical interest, because this group includes a large number of crop pests. Accordingly, the results of molecular studies can be used for molecular genotyping and correct identification of insect pests. Taking into account that the molecular organization and polymorphism of 5S rDNA remain still unexplored in species of the Drepanidae family, the aim of our work was to investigate the 5S rDNA of peach blossom (Thyatira batis L.), a representative of this family. The repeated unit of 5S rDNA was amplified by PCR, and the obtained DNA fragments were ligated into a plasmid vector. Plasmids containing the inserts were sequenced. It was found that two variants of IGS, 75- and 120-bp-long, respectively, are present in the 5S rDNA of T. batis, and the level of similarity between them amounts to 32% only. Therefore, T. batis possess the smallest size of the 5S rDNA IGS among all lepidopterans studied to date. Within the IGS, several variants of microsatellite sequences were found. In the long variant of the IGS in the position -22 bp a TATA-like motif was identified, which may be involved in transcription initiation, whereas in the short variant of the IGS this motif was lost due to deletion.