Investigation of self-incompatibility mechanism in some olive varieties using RNA-Seq method

Olive (Olea europaea) has three distinct fertilization traits: self-compatible, self-incompatible, and partially self-compatible. Self-incompatibility occurs as a result of the activation of a cellular response due to the coincidence of identical S alleles during pollen-pistil interaction. Incompatibility is a significant problem in olives, and it appears that significant gaps remain in the definition of the self-incompatibility mechanism. In this thesis, transcriptome analysis was conducted using the ILLUMINA High Seq 2000 sequencing platform, a Next Generation Sequencing technology, to elucidate the incompatibility mechanism and identify the genes causing incompatibility. In this study, flower tissues from the self-incompatible Kilis Yağlık and self-compatible Saurani varieties, collected at different times of year, were used, and histological analyses were performed to identify tissue samples from different developmental stages of the pollen tube. Sequencing yielded 11.14-19.28 GB of raw reads and 10-18 GB of clean reads for each library. Approximately 90% of the clean reads obtained were mapped to the reference genome, and approximately 20,000 transcripts belonging to each library were identified after mapping. Differences in the expression of genes causing discrepancies were detected in the 36-hour library. Significant changes were observed in the expression of genes related to cellular components such as thylakoids, photosystems, and cell membrane components; molecular functions including enzyme inhibitors, transmembrane transporters, and oxidoreductase activities; the ETS transporter system and hydrolysis enzymes; and biological processes such as cell recognition, pollination, pollen tube and pistil interaction, pollen recognition and elongation, and cell wall modification. KEGG analyses revealed significant roles in photosynthesis, pentose and glucuronate conversions, secondary metabolism and phenylpropanoid biosynthesis, ABC transporter proteins, and S-related pathways. As a result, it was determined that there were significant differences in the expression levels of S-locus, programmed cell death and pathogen resistance mechanisms in the self-compatible Saurani variety and the self-incompatible Kilis Yağlık variety.