The isolation, characterization and sequence of two divergent β-tubulin genes from soybean (Glycine max L.)

Mark Guiltinan, Din Pow Ma, Richard F. Barker, Mauricio M. Bustos, Richard Cyr, Ramin Yadegari, Donald E. Fosket

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Two divergent β-tubulin genes (designated Sβ-1 and Sβ-2) were isolated by screening a soybean genomic library with a Chlamydomonas reinhardtii β-tubulin cDNA probe. Restriction fragment analysis of the clones recovered, and of soybean genomic DNA, indicated that these represent two unique classes of structurally different β-tubulin genes in the soybean genome. However, it is possible that unidentified members of these classes or additional highly divergent classes of β-tubulin genes (thus far undetected) exist in the soybean genome. The Sβ-1 and Sβ-2 genomic clones were sequenced, revealing that both are potentially functional genes which would encode β-tubulins of 445 and 449 amino acids, respectively. A comparison of their derived amino acid sequences with β-tubulins from several organisms showed that they are most homologous to Chlamydomonas β-tubulin (85-87%), with lesser degrees of homology to β-tubulins of vertebrate species (79-83%), Trypanosoma brucei (80-81%) and Saccharomyces cerevisiae (66-68%). The amino acid sequences of Sβ-1 and Sβ-2 are as divergent from each other as they are from the Chlamydomonas β-tubulin. The amino acids at the diverged positions in Sβ-2 are nearly all conservative substitutions while in Sβ-1, 18 of the 69 substitutions were non-conservative. Both soybean β-tubulin genes contain two introns in exactly the same positions. The first soybean intron is located in the same position as the third intron of the Chlamydomonas β-tubulin genes. Codon usage in the two soybean β-tubulins is remarkably similar (D2=0.87), but differs from codon usage in other soybean genes.

Original languageEnglish (US)
Pages (from-to)171-184
Number of pages14
JournalPlant Molecular Biology
Issue number2
StatePublished - Mar 1 1987

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • General Biochemistry, Genetics and Molecular Biology


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