Abstract：Abstract Mediator is a large, modular protein complex, and plays the important roles in regulating transcription in eukaryotes. Growth and development of a plant are controlled by programmed expression of suits of genes at the appropriate time, tissue and abundance. Although mediator has been studied rapidly in recent years in Arabidopsis thaliana, but the expression profiling patterns of mediator subunits remains largely unknown. In this study, using the coding sequences (CDS) of mediator subunits in Arabidopsis thaliana as searching sequences, a total of 24 mediator subunits CDS were found in rice(Oryza sativa) by BLAST with nucleonic acid data base of NCBI. Med19 had two copies, all the rest had only one copy in rice among the obtained 24 genes. The expression profiles of 23 subunit genes based on 59 Affymetrix GeneChip samples of japonica rice were obtained by clustering method. In these subunit genes, OsMed12 had the highest specificity expression, the fellowing was OsMed11, all the rest 21 genes had differential expression even close to constitutive expression. Analysis of OsMed8 promoter activity by GUS expression showed that OsMed8 highly expressed in meristems, early stages of vegetative and reproductive development, which consistented with the expression profile of OsMed8 in clustering analysis. Results of subcellular locations of mediator subunits in Nicotiana benthamiana leaves indicated that OsMed6 was localized in nucleus, and OsMed8 was localized in both the nucleus and the plasma membrane. The results of the expression profiling patterns and subcellular locations of mediator subunits can provide useful informations for studying of their biological roles in rice.
