Among 81 α-tubulin cDNA clones prepared from RNA from maize seedling shoot, endosperm and pollen, we identified six different α-tubulin coding sequences. The DNA sequence analysis of coding and non-coding regions from the clones showed that they can be classified into three different α-tubulin gene subfamilies. Genes within each subfamily encode proteins that are 99 to 100% identical in amino acid sequence. Deduced amino acid sequence identity between genes in different subfamilies ranges from 89 to 93 %. The results of hybridizations of genomic DNAs to α-tubulin coding region probes and to 3′ non-coding region probes constructed from six different α-tubulin cDNA clones indicated that the maize α-tubulin gene family contains at least eight members. Comparison of deduced α-tubulin amino acid sequences from maize and the dicot species Arabidopsis thaliana showed that α-tubulin isotypes encoded by genes in maize subfamilies I and II are more similar to specific Arabidopsis gene products (96 to 97% amino acid identity) than to isotypes encoded by genes in the other maize subfamilies. Phylogenetic analyses revealed that genes in these two subfamilies were derived from two ancient α-tubulin genes that predate the divergence of monocots and dicots. These same analyses revealed that the gene in maize subfamily III is more closely related to sequences from subfamily I genes than to those from subfamily IT genes. However, the subfamily III gene has no close counterpart in Arabidopsis. We found evidence of a transposable element-like insertion in the subfamily III gene in some maize lines.
Bibliographical noteFunding Information:
We thank Dan Geraghty and Irwin Rubenstein for contributing the maize cosmid library for this study. We also thank Burle Gengenbach and the Department of Agronomy and Plant Genetics, University of Minnesota for providing field space and valuable advice. We thank John Larkin, Scott Schechter and Wang Duo for their help in the initial screening of cDNA libraries. We thank Mark Berres and John Doebley for their help in the phylogenetic analyses. This work was supported by funds from U.S. Department of Agriculture competitive research grants USDA 85-CRCR-l-1754, USDA 89-37261-4891, and USDA 89-37261-4910.
Copyright 2014 Elsevier B.V., All rights reserved.
- DNA insertion
- gene evolution
- gene family