In the Chlamydomonas reinhardtii cultures determination of the putrescine role on the tolerance of salinity and cold stress

Low temperature and salt stress are among the most important environmental stresses that limit the growth, development and yield of photosynthetic organisms. Polyamines and especially putresin have important roles in response to most environmental stresses. In this thesis, Chlamydomonas reinhardtii cultures were subjected to exogenous putrescine under low temperature and salinity stress. The changes in the expression of the psbA gene encoding the photosystem II D1 protein and the expression of the tba1 gene, which is one of the translational factors of the psbA gene, was determined by real-time PCR. In addition to genes for the repair mechanism of photosynthesis, genes encoding heat shock proteins (hsp70c, hsp90a, hsp90c), polyamine biosynthesis genes (odc2, spd1) under stress conditions and exogenous putrescine application were also determined. Physiologically, cell growth rate, amount of lipid peroxidation, antioxidant enzyme contents, and intrinsic ABA levels were also determined. It has been observed that low temperature and salinity stress causes a significant decrease in cell growth, an increase in lipid peroxidation rate, and a change in APX and CAT enzyme activities. It has been determined that in cultures in which exogenous putrescine is applied, gene expressions of heat-shock proteins are promoted in the first 24 hours in response to low temperature and in salt stress response in all concentrations at 7th days. According to the obtained results, the application of external putresin increased the level of intrinsic ABA, and increased the expression of psbA and tba1 genes in response to low temperature stress and salinity stress.