E. Drosopoulou et Zg. Scouras, THE ORGANIZATION OF THE ALPHA-TUBULIN GENE FAMILY IN THE DROSOPHILA-MONTIUM SUBGROUP OF THE MELANOGASTER SPECIES GROUP, Genome, 41(4), 1998, pp. 504-509
The alpha 1-, alpha 2-, alpha 3-, and alpha 4-tubulin genes have been
mapped by in situ hybridization to the polytene chromosomes of five sp
ecies representative of the Drosophila montium subgroup geographical d
istribution. A lambda phage clone containing al-tubulin specific seque
nces was isolated from a genomic DNA library of Drosophila auraria and
its restriction endonuclease pattern is presented. Both well-characte
rized heterologous and homologous probes were used to assess orthogona
lity of gene members between species groups. The in situ hybridization
pattern observed in all species studied is consistent with that of Dr
osophila melanogaster, since alpha 1-, a2-, and alpha 3-tubulin genes
are located on the same polytene arm, and the a4-tubulin gene is found
on a different arm. Cross-hybridization was observed among alpha 1-,
alpha 2-, and alpha 3-tubulin specific sequences in all species studie
d, using either heterologous or homologous probes. However, unlike D,
melanogaster, in all montium species studied, both alpha 1- and alpha
3-tubulin specific probes hybridize to the same polytene band, indicat
ing a clustered organization of the above genes. The chromosomal organ
ization of this gene family would suggest that taxa within the montium
subgroup are closer to their common ancestor than are the taxa in the
melanogaster species group. A mode of evolution for this gene family
in Drosophila is proposed.