Tissue-preferential expression of a rice alpha-tubulin gene, OsTubA1, mediated by the first intron

The genomic clone encoding an ol-tubulin, OsTubA1, has been isolated from r ice (Oryza sativa L.). The gene consists of four exons and three introns. R NA-blot analysis showed that the gene is strongly expressed in actively div iding tissues, including root tips, young leaves, and young flowers. Analys is of chimeric fusions between OsTubA1 and beta-glucuronidase (GLIS) reveal ed that the intron 1 was required for high-level GUS expression in actively dividing tissues, corresponding with normal expression pattern of OsTubA1. Fusion constructs lacking the intron 1 showed more GUS staining in mature tissues rather than young tissues. When the intron 1 was placed at the dist al region from S'-upstream region or at the 3'-untranslated region, no enha ncement of GUS expression was observed. Sequential deletions of the OsTubA1 intron 1 brought about a gradual reduction of GUS activity in calli. These results suggest that tissue-preferential expression of the OsTubA1 gene is mediated by the intron 1 and that it may be involved in a mechanism for an efficient RNA splicing that is position dependent.