A NUCLEOTIDE SUBSTITUTION IN ONE OF THE BETA-TUBULIN GENES OF TRICHODERMA-VIRIDE CONFERS RESISTANCE TO THE ANTIMITOTIC DRUG METHYL BENZIMIDAZOLE-2-YL-CARBAMATE

We characterized a Trichoderma viride strain that is resistant to the antimitotic drug methyl benzimidazole-2-yl-carbamate (MBC). This species has two beta-tubulin genes (tub1 and tub2) and by reverse genetics we showed that a mutation in the tub2 gene confers MBC resistance in this strain. Comparison of the tub2 sequence of the mutant strain with that of the wild type revealed that a single amino acid substitution of tyrosine for histidine at position 6 is responsible for the MBC tolerance. Furthermore, we showed that this gene can be used as a homologous dominant selectable marker in T viride transformation. Both tubulin genes were completely sequenced. They differ by 48 residues and the degree of identity between their deduced amino acid sequences is 86.3%.