Transcriptional profiling of genes responsive to abscisic acid and gibberellin in rice: phenotyping and comparative analysis between rice and Arabidopsis.

We collected and completely sequenced 32,127 full-length complementary DNA clones from Oryza sativa L. ssp. japonica cv. "Nipponbare." Mapping of these clones to genomic DNA revealed approximately 20,500 transcriptional units (TUs) in the rice genome. For each TU, we selected 60-mers using an algorithm that took into account some DNA conditions such as base composition and sequence complexity. Using in situ synthesis technology, we constructed oligonucleotide arrays with these TUs on glass slides. We targeted RNAs prepared from normally grown rice callus and from callus treated with abscisic acid (ABA) or gibberellin (GA). We identified 200 ABA-responsive and 301 GA-responsive genes, many of which had never before been annotated as ABA or GA responsive in other expression analysis. Comparison of these genes revealed antagonistic regulation of almost all by both hormones; these had previously been annotated as being responsible for protein storage and defense against pathogens. Comparison of the cis-elements of genes responsive to one or antagonistic to both hormones revealed that the antagonistic genes had cis-elements related to ABA and GA responses. The genes responsive to only one hormone were rich in cis-elements that supported ABA and GA responses. In a search for the phenotypes of mutants in which a retrotransposon was inserted in these hormone-responsive genes, we identified phenotypes related to seed formation or plant height, including sterility, vivipary, and dwarfism. In comparison of cis-elements for hormone response genes between rice and Arabidopsis thaliana, we identified cis-elements for dehydration-stress response as Arabidopsis specific and for protein storage as rice specific.