Cloning, Identification And Functional Analysis Of OsRAA1 Gene In Rice

FPF1 protein was firstly studied as a flowering promoting factor in mustard. It was indicated that FPF1 is involved in GA-dependent signaling pathway. And it may work synergistically with AP1 and LFY to modulate the competence to flowering in the shoot apical meristem. In the dissertation,AtFPF1 gene was transformed into rice. It is unfortunately that it just weakly promoted the heading of rice. On the contrary,it inhibited the root growth and promoted mature adventitious roots formation. These functions were just like those of the gene Oryza sativa Root Architecture Associated 1 (OsRAA1) which was cloned in rice. The protein shared 58% homology to the AtFPFI in Arabidopsis. It is the first report that the AtFPF1/OsRAA1 gene has a function to control root development in rice.The gene OsRAAl was located in chromosome 1 of rice based on the data of bioinformatics. Now this gene has been characterized molecularly. The OsRAAl gene encodes a 12.0 kDa protein. The results of in situ hybridization showed that its expression was detectable clearly in the apical meristem,the elongation zone of root tip,steles of the branch zone and the young lateral root. At the same time,its transcript also appeared in the young spike and lateral root primordia. Analysis of GUS activity,which was controlled by the promoter of OsRAAl gene,suggested that OsRAAl may be also expressed in the anther and palea/low palea. Constitutive expression of the gene under control of maize ubiquitin promoter resulted in inhibiting the growth of primary root,promoting the formation of adventitious roots,forming helix primary root in rice,which is similar to the phenotype of the plant treated with auxin. Its constitutive expression also caused the longer leaves and sterile of part florets at the late stage of plant development. The data of scan electronic microscope showed that flag leafs cells of the transgenic plant has been elongated more than those of the control. The analyses of Northen blot and GUS activity,which was controlled under OsRAAl promoter,demonstrated that the transcription of OsRAAl was induced by auxin. The gravitropic response was also delayed in the transgenicrice,which constitutively expressed OsRAAl. These data suggested that OsRAAl might be involved in the pathway of Auxin/IAA signal transduction in establishing the root architecture in rice.At the same time,many genes or ESTs were mined from the database showed that they have high homology to FPF1/OsRAA1 gene. From others and our data,it was suggested that there may be a FPF1/OsRAAl gene family in the plant which may be regulated by GA and auxin to control many aspects of plant development.