title: Molecular analysis and characterization of the Cochliobolus heterostrophus beta-tubulin gene and its possible role in conferring resistance to benomyl.
abstract: Cochliobolus heterostrophus Tub1 described here is the first beta-tubulin gene characterized from a naturally occurring benomyl-resistant ascomycete plant pathogen. The gene encodes a protein of 447 amino acids. The coding region of Tub1 is interrupted by three introns, of 116, 55, and 56 nt, situated after codons 4, 12, and 53, respectively. As a result of the preference for pyrimidines in the third position of the codons when a choice exists between purines and pyrimidines, codon usage in the Tub1 gene is biased. Tub1 shows high homology with beta-tubulin genes of other ascomycete species. However, Tub1 is exceptional in having Tyr(167), compared with Phe(167), possessed by beta-tubulin genes of other ascomycetes sequenced thus far. The Tyr(167) residue has been associated with benomyl resistance in other organisms. In contrast, all other benomyl-implicated residues of Tub1 correspond to sensitivity. Based on these results, we suggest that benomyl resistance in the fungus probably is attributed to Tyr(167).
authors.affiliation: Faculty of Agriculture, Kinki University, Nara 631-8505, Japan.
authors.forename: Abdul
authors.initials: A
authors.lastname: Gafur
authors.forename: Chihiro
authors.initials: C
authors.lastname: Tanaka
authors.forename: Kiminori
authors.initials: K
authors.lastname: Shimizu
authors.forename: Seiji
authors.initials: S
authors.lastname: Ouchi
authors.forename: Mitsuya
authors.initials: M
authors.lastname: Tsuda