Cloning And Functional Study Of Two Nitrate Reducase Genes In Rice

Functioning as a signal molecule, NO was reported to be involved in a variety of physiological processes in plant and animal. Up to present the resource and function of NO in plant remain unclear.Two putative nitrate reducase coding genes AK102363 (OsNR1) and AK102178 (OsNR2)in rice were cloned and Further qRT-PCR assays were performed to profile their expression responsing to various environmental factors.Our results showed that both of genes OsNR1 and OsNR2 were down regulated by the treatments of NaCI and 15% PEG which we used to mimic the salt and drought stresses and genes OsNR1 were down regulated significantly responding to low temperature. Consistent with the results of RealtimePCR a weaken fluorescence was observed in the root of rice under the treatments of NaCI and 15% PEG for 24h compared to the control.Both of two genes were able to be induced by SNP Which was used as a NO releaser. Both of genes displayed an asymmetric expression in shoot base of rice after gravistimulation. The expression of OsNR1 and OsNR2 were up regulated in the lower half of rice shoot base, at 6 hours after gravistimulation more than six-fold increase in expression of OsNR1 and OsNR2 were observed in the lower half shoot base compared to the upper half shoot base. In addition, the nia1nia2 and Atnoa1/rif1 mutants shown later response to the gravity,and which confirmed that NO involved in plant's gravity.Our data provided here showed that the two genes related to the generation of NO in vivo were dynamically regulated by environment factors including abio-stresses and gravistimulation suggested a essential role of NO to enhance plant fitness to withstand a variety of environmental constraints like salt, drought,cold and gravity.The ORF sequence of OsNR1 was cloned into plant transformation vector pcambia1302 and this construct was transformed into the wild type Arabidopsis Col-0,and NO deficient mutants Atnoa/rif and Atnia1/Atnia2. Our results showed that the rice NR encoding gene was able rescued the accumulation of NO and the tolerance to salts, in mutants Atnoa/rif and Atnia1/Atnia2. Furthermore, overexpression of OsNR1 in wild type Arabidopsis Col-0 resulted in early bolting and flowering suggesting that OsNR1gene may regulate important processes including plant stresses responses and development.