The Studies On Cat Isoenzymes Form Rice (Oryza Sativa L.) Response To Salinity Stresses

Plants frequently encounter stresses such as salinity, drought, heavy metal, radiation, low temperature, microbic infection; they adversely affect plant growth, development and productivity. The stability of plant internal redox environment and plant tolerance to stresses are closely related with system of scavenge the reactive oxygen.Catalase (EC 1.11.1.6 CAT) is one of the main antioxidant enzymes in Organisms that catalyzes the dismutation of H₂O₂ to water and dioxygen. CAT, along with hydroperoxidases and superoxide dismutases, serves as an efficient scavenger of reactive oxygen species (ROS), preventing cellular damage. As the modal plant of molecular biology research, the whole genome information of rice had been known to us, and the CAT gene of rice had been cloned. In rice, three catalase isozymes have been identified and characterized in various tissues. .The developmental expression pattern of each CAT is unique and complex. In this study, we did a particular research for the isoenzymes CAT1; CAT2; CAT 3 genes of riceTo understand the responsive relationship between CAT of rice and environmental stress, the transcription expression profile of CAT was studied by RT-PCR and Northern blot analysis using rice leaf and root in NaCl, NaHCO₃, Na₂CO₃, PEG6000, H₂O₂, and 4℃cool conditions. The results show that the accumulation of CAT mRNA was observed in these stresss, and the intensity of stresses influenced the expression of CAT. The tendency of increases and the time to the greater expression, between three isozymes, in different adverse circumstance demonstrate different. In the leaf, the increase of CAT1 gene expression to NaHCO₃, Na₂CO₃ stress compares CAT2 and CAT3 gene tendency to be obvious, in the root, the increase of CAT2 gene expression to NaCl, NaHCO₃, Na₂CO₃ stress tendency to be obvious, and in leaf and root, the increase of CAT3 gene expression to be more obvious with PEG6000 and cold treatment. The result show that, the identical CAT gene, is more sensitive to several different adverse circumstance stress, but to other adverse circumstance stress was inferior that other CAT is sensitive, in different organization, the CAT can also be different.To understand the genes function in vitro, the CAT1 and CAT3 genes were cloned into the prokaryotic vector. After the inducement with IPTG, the His-CAT1and His-CAT3 fusion protein were obtained.finally purified by Ni⁺-sepharose affinity column from denatured inclusionbody and analyzed by SDS-PAGE. There are some different between His-CAT1and His-CAT3 fusion protein. The recombinant His-CAT1, His-CAT3 protein activity was measured after renaturation. We obtained the protein with biological activities.The above research indicated that, the rice catalase gene is playing the vital role in the plant resistance external environment stress, the responsive relationship between CAT of rice and environmental stress, between the isozymes has certain difference, the fusion protein with biological activities was obtained after denaturation purifies and renaturation.