Temporal and spatial expression patterns of TUB9, a beta-tubulin gene of Arabidopsis thaliana.

Transgenic plants carrying chimeric genes composed of segments of the 5'-flanking region of the Arabidopsis 9-tubulin gene (TUB9) fused to the coding region of the beta-glucuronidase (GUS) gene of Escherichia coli were used to investigate the temporal and spatial patterns of TUB9 expression. Chimeric genes that contained at least 800 bp of TUB9 5'-flanking DNA were expressed primarily in floral tissues, with high levels of expression observed in pollen, elongating pollen tubes and ovules. The expression of the reporter genes in ovules ceased at the time of fertilization. In situ hybridization was used to verify that the reporter gene expression in pollen of transgenic plants is representative of the patterns of expression of the endogenous TUB9 gene. In situ hybridization also provided new insight into TUB9 transcript accumulation in ovules. The possible role of TUB9 and the functional implication of the largely non-overlapping expression patterns of tubulin genes are discussed.