Functional Study Of MAPKKs And The Contructions Of MicroRNAs Target Mimics

The abiotic factors including drought, salt, cold, severely restrict the crop production and quality. Especially, drought has become the important restriction factor of rice production in agriculture. The improvement of drought-resistant quality is particularly important when agricultural water is seriously of shortage.Mitogen activated protein kinase cascade plays a crucial role in translating the external stimuli into cellular responses, and is highly conserved in eukaryotes. In Arabidopsis MAPKKs can be rapidly activated when exposed to a variety of abiotic stresses including cold, drought, salinity. There have been six MAPKK genes cloned from rice and over-expressed in japonica in Previous experiments. Based on the analysis of transcript regulation by quantitative Real-timePCR and results of stress treatments of OsMKK-overexpressing transgenic seedling. We speculate that the function of OsMKK in stress resistance.There is a kind of mRNA,which is not cleaved but instead sequesters the corresponding miRNAs. Thus, the mRNA overexpression results in increased accumulation of corresponding miRNAs target mRNA. We coin the termtarget mimicry" to define this mechanism of inhibition of miRNAs activity. We tend to knockdown Oryza sativa miRNAs, which can be achieved by using artificial miRNAs target mimics. Thus, we can confirm the drought-resistant miRNAs according to the drought test. The main results are as follows:1. The expression of OsMKK gene family was analyzed using the Affymetrix rice genome array in three rice cultivars:Minghui 63, Zhenshan 97 and Shanyou 63 independently. Twenty-seven tissues sampled throughout the entire rice life-span were studied, with three hormone treatments (GA3, NAA and KT), which were applied to the seedling at the trefoil stage.OsMKK5 were up-regulated in the eheading stage andstamen showed that they may involved with flower development. OsMKK10-1 were expressed on the low level, but were up-regulated in calli, stamen and endosperm. The OsMKK genes were also found to be regulated in rice seedlings subjected to different hormone treatment conditions. 2. Analysis of transcript regulation by quantitative Real-timePCR revealed that these five members are differentially regulated by cold, heat, salinity and drought stresses except OsMKK10-2.3. Expression level is analyzed by Real-timePCR. Results show that OsMKK1 OsMKK3,OsMKK6 and OsMKK10 are over-expressed in their transplants except OsMKK4.4.OsMKK3 and OsMKK10-2 transgenic seedlings were treated with 150mM mannitol,150mM NaCl and 10M ABA.Results show that both the length and the fresh weight of OsMKK3 and OsMKK10-2 are insensitive to 150mM mannitol.5.OsMKK1,OsMKK3,OsMKK6 and OsMKK10-2 over-expressing lines are treated wite 30% PEG6000 until they are completely wilting. Then, translate the plants to normal condition. OsMKK1,OsMKK3 transplants recovered better than control,...