The β-tubulin gene family of Arabidopsis thaliana: preferential accumulation of the β1 transcript in roots

Abstract

The genome of Arabidopsis thaliana (L.) Heynh. was shown to contain a β-tubulin gene family consisting of at least seven distinct genes and/or pseudogenes. Genomic clones of five different β-tubulin genes and/or pseudogenes have been isolated and partially characterized. The complete nucleotide sequence of one A. thaliana β-tubulin gene, designated β1, has been determined. A comparison of the predicted amino acid sequence of the A. thaliana β1-tubulin with the predicted sequences of β-tubulins of animals and protists indicated that this plant β-tubulin shows a high degree of homology with other β-tubulins. However, the β1-tubulin contains a novel single amino acid insertion at position 41. The A. thaliana β1-tubulin gene is transcribed, as shown by RNA blot hybridization and S1 nuclease analyses. A 3'-noncoding gene-specific probe was used to examine the expression of the β1-tubulin gene in leaves, roots, and flowers by blot hybridization analyses of total RNA isolated from these tissues. The results showed that the transcript of the β1 gene accumulates predominantly in roots, with low levels of transcript in flowers, and barely detectable levels of transcript in leaves. A second genomic clone was shown to contain two essentially identical β-tubulin coding sequences in direct tandem orientation and separated by 1 kb.