A mutation in the α1-tubulin gene of Chlamydomonas reinhardtii einhardtii was isolated by using the amiprophos-methyl-resistant mutation apml-18 as a background to select new mutants that showed increased resistance to the drug. The upA12 mutation caused twofold resistance to amiprophos-methyl and oryzalin, and twofold hypersensitivity to the microtubule-stabilizing drug taxol, suggesting that the mutation enhanced microtubule stability. The resistance mutation was semi-dominant and mapped to the same interval on linkage group III as the tubulin gene. Two-dimensional gel immunoblots of proteins in the mutant cells revealed two electrophoretically altered α-tubulin isoforms, one of which was acetylated and incorporated into microtubules in the axoneme. The mutant isoforms co-segregated with the drug-resistance phenotypes when mutant upA12 was backcrossed to wild-type cells. Two-dimensional gel analysis of in vitro translation products showed that the non-acetylated variant α-tubulin was a primary gene product. DNA sequence analysis of the α1-tubulin genes from mutant and wild-type cells revealed a single missense mutation, which predicted a change in codon 24 from tyrosine in wild type to histidine in mutant upA12. This alteration in the predicted amino acid sequence corroborated the ~+1 basic charge shift observed for the variant α-tubulins. The mutant allele of the α1-tubulin gene was designated tua1-1.
|Original language||English (US)|
|Number of pages||10|
|Journal||Journal of cell science|
|State||Published - 1993|
- α-tubulin gene