As a higher eukaryotic organism, rice is a good model system to study the differences of gene expressions between differentiatedorgans and tissues on various developmental stages. Transcriptome profiling of these organs and tissues might serve as tools to understand basic mechanisms such as morphogenesis and organogenesis and can be exploited to develop organ markers and transcription factors which might be used to improve the agronomic traits in this important organism.
To understand tissue- and stage-specific gene expression, microarray experiments using rice 300k- and 60k chips were performed with 7 tissues including seed, root, leaf, flower and callus. All experiments were replicated to get reliable results and were compared between the microarrays. The hierarchical clustering of significantly expressed genes showed that thousands of genes were clustered showing organ specificity thus suggesting different set of genes were expressed in these organs and tissue. Especially, we couldclassify 1,200 genes exclusively expressed in each tissue and confirmed their expression patterns of several genes with semi-quantitative PCR(qPCR). Gus reporter under the control of those organ-specific genes are also being constructed to test the in-vivo gene expression. Furthermore, we found around 140 transcription factors expressed in tissue-specific manner among these organs and tissues. Additional analyses adopting over-expression of the transcription factors to reveal their functions and mechanisms are being in progress. Organ (Tissue)-specific transcriptome may serve as an important tool to understand gene expressions patterns and their relationship of organs at different developmental stages.

• Yeon-Ki Kim(GreenGene Biotech Inc. Genomics and Genetics Ins.)