Studies on the effects of proteasome inhibition on tomato

Plants encounter many abiotic and biotic stress factors that will adversely affect their growth and development throughout their life cycles. As a result of these stress conditions, they produce reactive oxygen species (ROS) and are exposed to oxidative stress. Plants have various antioxidants that provide detoxification of ROS in order to survive and cope with oxidative stress. By regulating gene expression in the cell, antioxidant production is altered and the damage caused by oxidative stress is reduced. The ubiquitin proteosome system (UPS) has been identified as an important system that plays a role in the processes of cell division, development, and response to abiotic and biotic stress in plants. It protects the cellular balance by breaking or processing damaged, misfolded and short-lived proteins in the cell. Proteosome inhibitors have been the main means of determining the role of ubiquitin in different biological processes of the proteosome system. MG132 is a strong, reversible, synthetic peptide aldehyde group proteosome inhibitor which is the most widely used in the studies. Studies have shown that cells affected by proteosome inhibition have higher ROS production. Accordingly, proteosomes are the direct regulatory mechanism of ROS production in plants. The relationship between proteosome inhibition and oxidative stress is well defined in yeast and mammalian cells. However, there is limited information about the response mechanisms of proteosome inhibition in plants. In this thesis study, Lycopersicon esculentum wild species were grown in Alfred Heilbronn Botanical Garden of Istanbul University and the seeds were used in tissue culture. Gene expression levels of SLGR1, SLPhGPX, SLCAT1, SLFe-SOD, SLGPX, SLCu/Zn-SOD, SLcAPX and SLGST genes which are known to be associated with antioxidant mechanisms, were determined by real-time PCR. As a result of the analysis, it was observed that there was no significant change in SLPhGPX, SLCAT1, SL-Fe-SOD and SLcAPX genes in root, stem and leaf tissues. In addition, expression of SLGR1 and SLGST genes in root tissue was increased. In leaf tissue, expression of SLGPX, SLCu/Zn-SOD and SLGST genes increased significantly. There was no significant change in the expression of the genes studied in the shoot tissue. It is thought that this information obtained from tomato root, stem and leaf tissues by creating proteosome inhibition will help to understand the relationship between antioxidant system and proteosome system in plants. Keywords: proteosome inhibition, MG132, Lycopersicon esculentum, proteosomal activity, antioxidant gene.