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

Abstract

The genomic clone encoding an α-tubulin OsTubAI, has been isolated from rice (Oryza sativa L.). The gene consists of our exons and three introns, RNA-blot analysis showed that the gene is strongly expressed in actively dividing tissues, including root tips, young leaves, and young flowers. Analysis of chimeric fusions between OsTubA1 and β-glucuronidase (GUS) revealed that the intron I was required for high-level GUS expression in acitively 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 I was placed at the distal region from 5'-upstream region or at the 3'-untranslated region, no enhancement of GUS expression was observed. Sequential deletions of the OsTubA1 intron I brought about a gradual reduction of GUS activity in calli. These results suggest that tissue-preferential expression of the OsTubAI gene is mediated by the intron I and that it may be involved in a mechanism for an efficient RNA splicing that is position dependent.