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Published online by Cambridge University Press: 12 February 2007
Membranous cDNA microarrays containing 2200 unique rice transcripts were designed for screening the characteristics of spatially expressed genes in post-germination rice seedlings. By comparing the profiles obtained, 31 genes were identified as expressed specifically in the plumule, 36 in the mesocotyl and 73 in the radicle. Several genes, such as polyubiquitin, UDP-glucose pyrophosphorylase, sucrose synthase and phosphoglycerate kinase, which encode components of the carbohydrate or protein metabolic reaction cascades, were expressed specifically in the mesocotyl, indicating that degradation reactions of the endospermous reserve starch and proteins occur mainly in the mesocotyl during the post-germination stage. A number of genes involved in defence mechanisms or in the processes of replication, transcription and translation were identified as expressed specifically in the plumule or radicle. Among plumule specifically expressed genes, translation initiation factor 5a, 40s ribosomal protein s28 and ribosomal protein 136 are considered to have a critical role in protein biosynthesis; while allergenic protein, β-D-glucan exohydrolase and actin 11 are genes with defending functions. Among the catalogue of radicle specifically expressed genes, EF-1a, Tat binding protein, replication protein A2, histone h3.2, ribosomal protein s29a and 40s ribosomal protein s19 are genes that function in the process of replication, transcription or translation; whereas glycine-rich protein, wound-induced basic protein, Bowman-Birk proteinase inhibitor and lipid transfer protein-2 are genes involved in defence responses. Results of this experiment have provided insight into post-germination molecular physiology at the genomic level of gene expression.