Study On The Effects Of Ectopic Expression Of A Glutamate Dehydrogenase Gene,MgGDH,from Magnaporthe Grisea On Dehydration Stress In Rice

Background GDH may be act as a stress-responsive enzyme in detoxification of high intracellular ammonia and production of glutamate for proline synthesis under stress conditions. GDHs in higher plants have lower affinities for ammonium, GDHs from lower organisms were introduced into plants so as to improve the drought resistance. To breed the new varieties of rice that are tolerant to sereve drought, MgGDH was cloned and introduced into rice, then objective the influence of drought stress and osmotic stress. The main results of this study are as follows:1. MgGDH with size of 1392 bp was cloned from the Magnaporthe grisea2. Aims the objective of this study was t o investigate MgGDH, Methods Prokaryotic expression and purified recombinant His-TF-MgGDH and His-TF-Os GDH proteins, receive the recombinant proteins size of 106.5 k Da and 126.1 k Da. respectively were used to analyze their kinetic properties. Results the NADP（H）-GDH activity of His-T F-MgGDH was significantly higher than that of His-TF-Os GDH. T he amination activity wa s significantly higher than deamination activity in both His-T F-MgGDH and His-T F-Os GDH. It is noteworthy that the affinity of His-TF-MgGDH for ammonium（Km = 0.67 ± 0.05 mM） was substantially higher than that for glutamate（Km = 22.3 ± 0.81 m M）. The results indicate that His-TFMgGDH tends to utilize ammonium to produce L-glutamate3. Aims the objective of study was to investigate transgenic rice plants with over-expression of MgGDH tolerance to dehydration stress. PEG and soil drought were disposed the Transgenic rice plants and wild-type plants. Results Transgenic rice plants with over-expression of MgGDH show higher tolerance to dehydration str ess than wild-type plants.4. Results the NADP（H）-GDH activity of transgenic plants was significantly higher than that of wild-type plants. Moreover, the amination activity wa s significantly higher than deamination activity. Compared with wild-type plants, the transgenic plants accumulated significantly lower NH₄⁺ and more glutamate, proline and soluble sugar under dehydration stress conditions. Real-time PCR results demonstrated that the expression levels of proline synthetase and proline transport genes w ere significantly higher in transgenic plants than in the wild-type plants. These results indicate that heterologous expression of MgGDH can accumulated much less NH4 but higher amounts of proline and soluble sugar under dehydration stress conditions to prevent toxic accumulation of ammonium and in return improve dehydration stress tolerance in rice.Conclusions Heterologous expression of MgGDH could improve the dehydration stress tolerance in rice.