Isolation and characterization of 1-deoxy-d-xylulose 5 phosphate reductoisomerase (DXR) and terpene synthase genes in Sütçüler oregano (Origanum minutiflorum)

Origanum minutiflorum, also known as 'Sütçüler Kekiği', is an endemic species that grows in the Sütçüler region of Isparta province, Turkey. The aim of this study is to isolate and characterize the 1-deoxy-D-xylulose 5-phosphate reductoisomerase (OmDXR) and terpene synthase 1 (OmTPS1) genes involved in the synthesis of essential oil from Origanum minutiflorum plant. In accordance with this objective, total RNA was isolated from thyme leaves, and a series of molecular procedures were carried out using specific primers targeting the target genes. As a result of the study, it was determined that the full-length cDNA nucleotide length of the OmDXR gene is 1 700 bp, and it contains the open reading frame region of the gene, which is 1 446 bp. The gene was found to contain a 5'-UTR of 138 bp and a 3'-UTR of 116 bp, with the coding region encoding a protein of 481 amino acids in length. Furthermore, the nucleotide sequence obtained in this study showed a similarity of 74.22% to 81.07% with previously obtained nucleotide sequences from other studies. Similarly, the protein sequence showed a similarity of 70.92% to 72.95% with the protein sequences from those previous studies. The full-length cDNA nucleotide sequence of the OmTPS1 gene was found to be 1 836 bp long, and 1 806 bp of the gene was identified to be the open reading frame region. The protein encoded by the OmTPS1 gene was found to be 601 amino acids long. Additionally, in the aim of this study, it was determined that the nucleotide sequence obtained showed similarity with the sequence lengths obtained from previous studies at a range of 75.99% to 89.58%, while the protein sequence showed similarity at a range of 51.66% to 69.88%. In addition, within the scope of the thesis, a 'Southern Blot' analysis was conducted to determine the copy number of the OmDXR and OmTPS1 genes in the Origanum minutiflorum genome. The results of the 'Southern Blot' analysis of the characterized genes revealed that both genes (OmDXR and OmTPS1), when digested with three different enzymes (EcoRI, BamHI, and HindIII), produced a single DNA band, indicating that they exist as single copies in the genome.