Change in cysteine synthase gene function in Arabidopsis old3 mutant plants in response to oxidative stress-induced by cadmium chloride

Arabidopsis mutant old3 (Onset of Leaf Death3) has a EMS mutation in Cysteine synthase gene(AT4G14880). One of the important functions of this gene is plant detoxification against oxidative stress. Old3 plants exposed to cadmium go through plant cell death after 12 days at 22˚C. Since the growth and development of old3 plants return to a normal situation at 28˚C, this research was performed to evaluate old3 plant responses to cadmium at 28˚C and 22˚C and compared with the wild type plants, Landsberg erecta (Ler-0). Therefore several traits including germination rates, growth rates and fresh weights were studied. POD and CAT enzyme activities were assayed in mutant seedlings. In addition, the relative expression levels of two marker genes, DEFL and GST1, which are involved in oxidative stress was measured. Factorial statistical design based on a completely randomized design was used to analyze the data. The plants growth, fresh weight and germination rate under the cadmium stress at 28˚C were higher than those under 22˚C, and it happened more clearly in the mutant plants. The result suggested that the resistance of wild type was higher at both two 28˚C and 22˚C. The investigation of POD enzyme activity at 28˚C indicated higher activity in the mutant plants compare to wild type. Furthermore, the relative expression levels of DEFL and GST1 genes in the mutant old3 plants were enormously higher than those of wild type at 28˚C. As a result, it was found that although the growth and development of old3 plants could be recovered by the temperatures, but the mutant old3 plants were more sensitive to the cadmium contamination compared to the wild type Ler-0 plants at both temperature and could not be recovered into the wild type responses at 28˚C.