| Sister chromatid cohesion is essential for accurate chromosome separation and segregation during meiosis and mitosis. Cohesion is established in the S phase, by a phylogenetically conserved multi-protein complex called cohesin, to link newly replicated sister chromatids together until removed from chromosomes in proper time. In budding yeast, cohesin at least includes Scc1, Scc3, Smc1 and Smc3 four subunits in mitosis, but Scc1 is replaced by its meiosis-specific variant, Rec8 in meiosis. At present, many genes associated with cohesin have been isolated from several higher eukaryotic organisms such as Caenorhabditis elegans, Drosophila melanogaster, Homo sapiens, Mus musculus and Arabidopsis thaliana. However, functional analysis for these genes has not been widely carried out. And many basic issues about meiosis and mitosis are still unclear even in yeast. Furthermore there are great differences about the mechanisms of meiosis between different organisms.We have isolated all the four RAD21/REC8-like genes from Oryza sativa; and each of them exists in genome with a single copy. There is no similarity between them at nucleotide level. The similarity for the 4 polypeptides encoded by the 4 genes is mainly concentrated in their N- and C-terminal domains. Their middle sequences between the two conserved domains contain potential nuclear targeting motif, PEST motif, separase recognition site and many phosphorylation sites.Results from semi-quantitative RT-PCR, in situ hybridization and Western blotting have showed that the 4 genes have different expression dynamics during flower development although they all are expressed preferentially in reproductive organs. Both OsRAD21-1 mRNA and OsRAD21-3 mRNA have the highest accumulation amount in flowers at meiosis stage, but there is also high amount for OsRAD21-3 mRNA in pollen. The highest accumulation amount for OsRAD21-4 mRNA presents in flowers at pre-meiotic stage, however for OsRAD21-2 mRNA at... |
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