Tubulins are encoded by small gene families in plants. Here we report the cloning and characterization of water foxtail α-tubulin genes (AaTUA), an economically important weed. The genome of water foxtail contains TUA family consisting of at least four genes. Using degenerate primers, four partial TUA genes were isolated from the complementary DNA (cDNA) of water foxtail. Using the partial gene sequences, specific primers for each TUA gene were designed and full-length TUA cDNAs were isolated. These genes were designated as AaTUA1 to AaTUA4. The deduced amino acid sequences of AaTUA genes showed significant homology to the TUA genes of barley, corn, and Arabidopsis. The coding sequences of the AaTUA1 and AaTUA3 genes were interrupted by three introns and there were four introns in the coding regions of AaTUA2 and AaTUA4. The organ-specific expression of AaTUA genes showed that AaTUA1 and AaTUA4 were predominantly expressed in all organs examined (root, stem, young leaf, mature leaf, and panicle), whereas AaTUA2 was expressed mainly in roots and AaTUA3 was expressed in stem, root, and panicle. Abscisic acid (ABA) and gibberellic acid (GA) differentially induced the expression of AaTUA1 and AaTUA3. Moreover, trifluralin, propham, and caffeic acid induced the expression of all AaTUA genes in a dose-dependent manner except AaTUA2. This is the first report of complete sequences of AaTUA genes and the first characterization of these genes for any Alopecurus species in the literature.

Nomenclature: Water foxtail, Alopecurus aequalis Sobol Arabidopsis, Arabidopsis thaliana L.; barley, Hordeum vulgare Lcorn, Zea mays L