Investigation of the alleviating effect of silicone against UV-B stress in Arabidopsis thaliana

Today, due to global warming and the problems it brings, agricultural lands and natural vegetation in the world are exposed to various biotic and abiotic stress factors. Agricultural lands are the basis for meeting the food needs that arise with the increasing world population, but not only in the field of food; it also plays a critical role in healthcare, cosmetics, and various industrial fields. Ensuring the adaptation of plants to stress conditions and elucidating the molecular mechanisms underlying this adaptation are of great importance. One of the biggest factors brought by global warming and the depletion of the ozone layer is ultraviolet-B (UV-B) type radiation reaching the Earth's surface. It has been shown in previous studies that UV-B-type radiation with a wavelength in the range of 280-320 nm has adverse effects on plants. In the study, the wild-type plant Arabidopsis thaliana Columbia (Col-0) was used as a model organism. UV-B radiation application was optimized to 800 µWatt/cm2 for 60 minutes on 17-day-old A. thaliana. In this thesis study, the effects of the silicon molecule on A. thaliana exposed to UV-B radiation were investigated by performing physiological, gene expression, and epigenetic level analyses. The effects of silicon molecule on plants on multi-stress resistance and especially UV-B radiation resistance have been shown in previous studies. However, the molecular mechanisms underlying this effect have not yet been elucidated. For this reason, osmolyte accumulation and cell membrane ion leakage analysis were performed within the scope of the thesis. In addition, expressions of DGK2, CHS, FLC, Rad51, and UVR8 genes, which are known to be associated with abiotic stress response in plants, were determined using real-time polymerase chain reaction. In this way, the relationship between the stress response of silicon to UV-B application and the expression of the specified genes has been demonstrated. In addition, DNA methylation percentages at the genome level were measured and compared in order to better understand the UV-B stress response, which is known to be associated with epigenetic regulation in plants. As a result of the thesis study, in vitro 1 mM silicon application has been shown to have physiological, gene expression, and epigenetic level effects on A. thaliana Col-0 under 800 µWatt/cm2 UV-B radiation stress. While osmolyte accumulation was found to be higher in the experimental groups to which only silicone was applied, compared to the control, cell membrane ion leakage was measured as low. In gene expression analyzes, significant changes were recorded in the expression of target genes, indicating that silicon plays a supportive role in the stress response. Finally, in measuring DNA methylation percentages at the genome level, the percentage of genomic DNA methylation increased in silicon-treated experimental groups compared to the control group. Within the scope of the study, it has been shown that the silicon molecule causes changes at the molecular level in plants. While this study contributes to the literature on the use of silicon as an agent in plant stress response, it is presented as an example of the use and testing of similar molecules against biotic and abiotic stresses.